Patent Publication Number: US-2012030995-A1

Title: Processes for producing alcohols from a mixed acid feed

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. application Ser. No. 12/889,260, filed Sep. 23, 2010, which claims priority to U.S. Provisional Application No. 61/300,815, filed Feb. 2, 2010, U.S. Provisional Application No. 61/332,727, filed May 7, 2010, and U.S. Provisional Application No. 61/332,696, filed May 7, 2010, the entireties of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to processes for producing mixed alcohol compositions and, in particular, to processes for producing mixed alcohol compositions via the hydrogenation of acetic acid and a higher acid to form ethanol and a higher alcohol. 
     BACKGROUND OF THE INVENTION 
     Ethanol is often produced for and utilized as a component in various consumable products, e.g., beer, wine, and spirits. Typically, ethanol intended for such uses is produced via fermentation. Many government agencies impose high duties or taxes on consumable ethanol, thereby increasing the cost to consumers. 
     There are, however, many other uses for ethanol that do not involve consumption, e.g., fuels, chemical solvents, or pharmaceuticals. As such, in an effort to provide inexpensive ethanol for non-consumable uses, the duties or taxes imposed on consumable ethanol are typically not required for ethanol that is not intended to be consumed. To ensure that such ethanol compositions are used for non-consumable applications, most countries have laws and regulations requiring that these ethanol compositions include a denaturant, which is added to an otherwise substantially pure ethanol composition in order to render the ethanol non-potable. Thus, ethanol compositions that include a denaturant and which are not intended for consumption are commonly referred to as “denatured ethanol” or “denatured alcohol.” Conventional denaturants include methanol, isopropyl alcohol, acetone, methyl ethyl ketone, ethyl acetate, methyl isobutyl ketone, and acetaldehyde. 
     The processing step of adding a denaturant to an otherwise potable ethanol composition adds complication and cost to in conventional processes for forming denatured ethanol. Thus, the need exists for new and improved processes for forming denatured ethanol. 
     SUMMARY OF THE INVENTION 
     In a first embodiment, the present invention is directed to a process for producing an alcohol composition, the process comprising the steps of hydrogenating a mixed acid feed comprising acetic acid in an amount from 80 to 99 wt. % and a higher acid, e.g., propionic acid, in an amount from 0.01 to 20 wt. %, optionally at least 0.04 wt. % or at least 0.08 wt. %, in the presence of a catalyst to form a crude alcohol product comprising ethanol and a higher alcohol, e.g., propanol; and separating the crude alcohol product in one or more separation units to form an alcohol composition and one or more derivative streams, wherein the alcohol composition comprises ethanol in an amount greater than 80 wt. %. The alcohol composition may comprise a small quantity of higher alcohols, e.g., less than 1.0 wt. % or less than 0.5 wt. %, or a more appreciable quantity of higher alcohols, e.g., from at least 0.5 wt. %, from 0.01 to 20 wt. %, from 0.04 to 20 wt. %, from 0.5 to 10 wt. %, from 1 to 8 wt. %, or from 2 to 5 wt. %. 
     In another embodiment, the invention is to a process for producing a mixed alcohol composition, the process comprising the steps of hydrogenating a mixed acid feed comprising acetic acid and a higher acid in the presence of a catalyst to form a crude alcohol product comprising ethanol and a higher alcohol; and separating the crude alcohol product in one or more separation units to form a mixed alcohol composition and one or more derivative streams, wherein the mixed alcohol composition comprises ethanol in an amount greater than 60 wt. % and the higher alcohol in an amount from 0.01 wt. % to 40 wt %, based on the total weight of the mixed alcohol composition. 
     The resulting alcohol composition optionally comprises from 92 wt. % to 99 wt. % ethanol and from 0.01 to 8 wt % propanol, e.g., from 0.04 to 8 wt %, from 0.5 to 8 wt %, from 1 to 8 wt % or from 2 to 5 wt. %. The crude alcohol product may further comprise other components such as from 0.01 wt. % to 20 wt. % ethyl acetate; from 0.01 wt. % to 10 wt. % acetaldehyde; from 0.01 wt. % to 10 wt. % isopropanol; from 0.01 wt. % to 20 wt. % diethyl ether; from 0 wt. % to 90 wt. % acetic acid; from 0.001 to 5 wt. % higher ester; and from 5 wt. % to 35 wt. % water, based on the total weight of the crude ethanol product. 
     In one aspect, the mixed acid feed comprises acetic acid, the higher acid and acetone, and the crude alcohol product further comprises isopropanol. In this aspect, the process optionally comprises contacting acetic acid and hydrogen, in an auxiliary reactor, under conditions effective to form the acetone. The alcohol composition, as formed, may comprise from 0.1 wt. % to 10 wt % isopropanol, based on the total weight of the alcohol composition. 
     The separating step may vary widely, but in one embodiment comprises eparating a first portion of the crude alcohol product into an ethanol stream and a higher alcohol stream; purifying the ethanol stream to form a purified ethanol stream; and combining at least a portion of the higher alcohol stream with the purified ethanol stream to form the alcohol composition. 
     In another embodiment, the invention is to a process for producing a denatured mixed alcohol composition, the process comprising the steps of hydrogenating acetic acid and one or more higher acids in the presence of a catalyst to form a crude alcohol product comprising ethanol and a higher alcohol; separating the crude alcohol product into: (i) a mixed alcohol composition comprising ethanol in an amount greater than 60 wt. % and the higher alcohol in an amount greater than 0.01 wt. %, e.g., greater than 0.04 wt. %, greater than 0.08 wt. % or greater than 1 wt. %, and (ii) one or more derivative streams; and blending the mixed alcohol composition with a minor amount of a fuel denaturant to form a denatured mixed alcohol composition. The denatured mixed alcohol composition preferably comprises the fuel denaturant in an amount from 1.5 to 3.0 wt. %. In one aspect, the denatured mixed alcohol composition comprises from 92 to 98 wt. % ethanol, from 0.01 to 20 wt. % propanol (e.g., from 0.5 to 8 wt % propanol) and from 1.5 to 3 wt. % fuel denaturant. The denatured mixed alcohol composition preferably comprises no more than 1.0 wt. % water. The fuel denaturant optionally is selected from the group consisting of natural gasoline, gasoline blendstocks or unleaded gasoline or comprises diesel fuel. The invention also relates to methods of blending the denatured mixed alcohol composition with a basestock such as diesel fuel or gasoline to form a fuel blend, e.g., E10, E15, E85 or E-Diesel. 
     In another embodiment, the invention is to a process for producing a mixed alcohol composition, the process comprising the steps of hydrogenating a mixed acid feed in the presence of a catalyst to form a crude alcohol product comprising ethanol and a higher alcohol; separating the crude alcohol product into an ethanol stream and a higher alcohol stream; further purifying the ethanol stream to form a purified ethanol stream; and combining at least a portion of the purified ethanol stream with at least a portion of the higher alcohol stream to produce the mixed alcohol composition. In exemplary aspects of this embodiment, the mixed alcohol composition comprises from 50 to 99 wt. % ethanol, and from 0.01 to 40 wt. % higher alcohol, e.g., propanol, or from 92 to 99 wt. % ethanol and from 0.5 to 8 wt % higher alcohol, e.g., propanol. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention is described in detail below with reference to the appended drawings, wherein like numerals designate similar parts. 
         FIG. 1A  is a schematic diagram of a hydrogenation system in accordance with one embodiment of the present invention. 
         FIG. 1B  is a schematic diagram of the system shown in  FIG. 1A  with a return of the distillate of a second column to the reactor zone. 
         FIG. 1C  is a schematic diagram of a hydrogenation system in accordance with one embodiment of the present invention. 
         FIG. 2  is a schematic diagram of a separation scheme comprising two separation columns and a water separation unit in accordance with one embodiment of the present invention. 
         FIG. 3  is a schematic diagram of a separation scheme comprising two separation columns in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Introduction 
     Conventional denatured ethanol preparation processes begin with the production of a purified ethanol. In these processes, ethanol may be formed and subsequently purified by conventional methods. A denaturant is then added to the purified ethanol to form the denatured ethanol. 
     The present invention relates to processes for producing alcohols such as ethanol and propanol from a mixed acid feedstock. It has now been discovered that catalysts suitable for the hydrogenation of acetic acid to form ethanol also may tolerate higher acids, such as propionic acid. Moreover, the catalysts may beneficially catalyze the hydrogenation of the one or more higher acids to the corresponding higher alcohols, such as propanol. In this context, the term “higher” means C 3+  compounds. The resulting crude mixed alcohol product may be separated to form a product ethanol stream and a product higher alcohol stream (preferably a product propanol stream), or may be purified as a mixed alcohol product and made salable, for example, as a mixed alcohol composition, optionally a denatured ethanol composition, in which the denaturant comprises one or more higher alcohols, preferably propanol. 
     Thus, in one embodiment, the invention is to a process comprising the steps of hydrogenating acetic acid and one or more higher acids in the presence of a catalyst to form a crude alcohol product comprising ethanol and one or more higher alcohols, preferably propanol. As used herein, unless otherwise specified, the term “propanol” refers to n-propanol and isopropanol in combination. Preferably, the crude alcohol product comprises ethanol in an amount greater than 60 wt. % and the one or more higher alcohols, preferably propanol, in an amount from 0.1 to 40 wt. %. 
     In one embodiment, the higher alcohols may act as denaturants that are co-produced with the ethanol. In another embodiment, the higher alcohols are formed as a by-product of the hydrogenation reaction. In other words, the higher alcohols are formed in situ with the ethanol. The processes of the present invention, in one embodiment, further comprise separating the crude ethanol product into a mixed alcohol composition, optionally a denatured ethanol composition, and one or more derivative streams. The separating may be performed in one or more, e.g., two or more, or three or more, separation units, e.g., distillation columns. The resultant mixed alcohol composition, as formed, is derived from acetic acid and one or more higher acids and comprises from 0.01 wt. % to 40 wt. % higher alcohols, e.g., from 0.01 wt. % to 25 wt. %, from 0.01 wt. % to 20 wt. %, or from 1 wt. % to 15 wt. %, and from 50 wt. % to 99 wt. % ethanol, e.g., from 60 wt. % to 99 wt. % or from 70 wt. % to 95 wt. %, based on the total weight of the mixed alcohol composition. Thus, by forming the higher alcohol in situ along with the ethanol in the hydrogenation step, the inventive processes may produce a mixed alcohol composition, e.g., a denatured ethanol composition, more efficiently and may reduce processing steps. In particular, the processes of the present invention may eliminate the need for separately producing or obtaining a denaturant and subsequently adding the denaturant to ethanol. 
     The processes of the invention may be beneficial, for example, in forming mixed alcohol compositions that are suitable for blending into various petroleum fuels. As an example, at ethanol contents of 20% and higher, ethanol/Diesel blends (“E-Diesel”) cannot be uniformly mixed or blended into one phase without rapid phase separation at temperatures lower than 10° C. Since they cannot be uniformly mixed into one phase and stored for easy use, the components typically must be mixed just prior to use and temperatures below 10° C. should be avoided. One solution to this problem is to blend ethanol with higher alcohols resulting in a mixed alcohol composition that may be blended into diesel fuel oil with reduced or eliminated phase separation issues at normal ambient conditions. See, e.g., U.S. Pat. Nos. 4,527,995 and 5,720,784, and L. R. Waterland et al.,  Safety and Performance Assessment of Ethanol/Diesel Blends  ( E - Diesel ), NREL/SR-540-34817, at p. 1-1 (September 2003), the entireties of which are incorporated herein by reference. 
     Thus, in one embodiment, the invention is a process for forming a mixed alcohol composition for diesel fuel use comprising the steps of hydrogenating acetic acid and one or more higher acids in the presence of a catalyst to form a crude alcohol product comprising ethanol and one or more higher alcohols, preferably propanol, although for improved blending C 4+  acids in the feed and C 4+  alcohols in the crude alcohol product may be desired. The crude alcohol product is separated into a mixed alcohol composition comprising ethanol and the higher alcohol, and one or more derivative streams. The mixed alcohol composition may then be blended with a minor amount of diesel fuel denaturant, e.g., diesel fuel oil, to form a denatured mixed alcohol composition for diesel fuel use. The denatured mixed alcohol composition for diesel fuel use preferably comprises from 0.5 to 4 wt. % diesel fuel denaturant, at least 15 wt. % ethanol (e.g., 75-98 wt. % ethanol or 90-98 wt. % ethanol), and at least 0.01 wt. % heavier alcohol (e.g., propanol), e.g., at least 0.04 wt. %, at least 0.5 wt. %, at least 1 wt. %, at least 2 wt. % or at least 5 wt. % heavier alcohol. The invention also relates to processes for blending such denatured mixed alcohol compositions with diesel fuel to form an E-Diesel fuel composition, preferably comprising from 10 to 15 wt % ethanol. 
     Alternatively, the mixed alcohol composition may be blended with a minor amount of a gasoline fuel denaturant, e.g., natural gasoline, gasoline blendstocks or unleaded gasoline, as defined in ASTM D4806-11, the entirety of which is incorporated herein by reference, to form a denatured mixed alcohol composition. The denatured mixed alcohol composition for gasoline fuel use preferably comprises from 1.5 to 3.0 wt. % gasoline fuel denaturant, at least 92.1 wt. % ethanol (as determined by ASTM D5501, the entirety of which is incorporated herein by reference), and at least 0.01 wt. % heavier alcohol (e.g., propanol), e.g., at least 0.04 wt. %, at least 0.5 wt. %, at least 1 wt. %, at least 2 wt. % or at least 5 wt. % heavier alcohol. The denatured mixed alcohol composition preferably comprises no more than 1.0 wt. % water as determined by ASTM E203. The invention also relates to processes for blending such denatured mixed alcohol compositions with a gasoline fuel to form an ethanol/gasoline composition, optionally an E10, E15, or E85 fuel composition, optionally comprising from 5 to 40 wt. % ethanol, e.g., from 10 to 15 wt % ethanol, about 10 wt. % ethanol, or about 15 wt. % ethanol, or about 85 wt. % ethanol, the remainder consisting essentially of gasoline. 
     Hydrogenation Process 
     Suitable hydrogenation catalysts include catalysts comprising a first metal and optionally one or more of a second metal, a third metal or additional metals, optionally on a catalyst support. The first and optional second and third metals may be selected from Group IB, IIB, IIIB, IVB, VB, VIIB, VIIB, VIII transitional metals, a lanthanide metal, an actinide metal or a metal selected from any of Groups IIIA, IVA, VA, and VIA. Preferred metal combinations for some exemplary catalyst compositions include platinum/tin, platinum/ruthenium, platinum/rhenium, palladium/ruthenium, palladium/rhenium, cobalt/palladium, cobalt/platinum, cobalt/chromium, cobalt/ruthenium, silver/palladium, copper/palladium, nickel/palladium, gold/palladium, ruthenium/rhenium, and ruthenium/iron. Exemplary catalysts are further described in U.S. Pat. No. 7,608,744 and U.S. Publication Nos. 2010/0029995 and 2010/0197485, the entireties of which are incorporated herein by reference. 
     In one exemplary embodiment, the catalyst comprises a first metal selected from the group consisting of copper, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, titanium, zinc, chromium, rhenium, molybdenum, and tungsten. Preferably, the first metal is selected from the group consisting of platinum, palladium, cobalt, nickel, and ruthenium. More preferably, the first metal is selected from platinum and palladium. When the first metal comprises platinum, it is preferred that the catalyst comprises platinum in an amount less than 5 wt. %, e.g., less than 3 wt. % or less than 1 wt. %, due to the high demand for platinum. 
     As indicated above, the catalyst optionally further comprises a second metal, which typically would function as a promoter. If present, the second metal preferably is selected from the group consisting of copper, molybdenum, tin, chromium, iron, cobalt, vanadium, tungsten, palladium, platinum, lanthanum, cerium, manganese, ruthenium, rhenium, gold, and nickel. More preferably, the second metal is selected from the group consisting of copper, tin, cobalt, rhenium, and nickel. More preferably, the second metal is selected from tin and rhenium. 
     If the catalyst includes two or more metals, e.g., a first metal and a second metal, the first metal optionally is present in the catalyst in an amount from 0.1 wt. % to 10 wt. %, e.g., from 0.1 wt. % to 5 wt. %, or from 0.1 wt. % to 3 wt. %. The second metal preferably is present in an amount from 0.1 wt. % and 20 wt. %, e.g., from 0.1 wt. % to 10 wt. %, or from 0.1 wt. % to 5 wt. %. For catalysts comprising two or more metals, the two or more metals may be alloyed with one another or may comprise a non-alloyed metal solution or mixture. Thus, in one embodiment, the catalyst is substantially free of alloys. In one embodiment, where the catalyst comprises a first metal that is a Group VIII noble metal, the catalyst may be substantially free of any additional metals capable of alloying with the Group VIII noble metal, e.g., containing less than 10 wppm, less than 1 wpmm or less than 0.1 wppm of such second metals. 
     The preferred metal ratios may vary depending on the metals used in the catalyst. In some exemplary embodiments, the mole ratio of the first metal to the second metal is from 10:1 to 1:10, e.g., from 4:1 to 1:4, from 2:1 to 1:2, from 1.5:1 to 1:1.5 or from 1.1:1 to 1:1.1. 
     The catalyst may also comprise a third metal selected from any of the metals listed above in connection with the first or second metal, so long as the third metal is different from the first and second metals. In preferred aspects, the third metal is selected from the group consisting of cobalt, palladium, ruthenium, copper, zinc, platinum, tin, and rhenium. It should be noted, however, that in some embodiments, the catalyst is substantially free of rhenium meaning that it contains less than 10 wppm rhenium, less than 1 wppm or less than 0.1 wppm. 
     In another aspect, the catalyst is substantially free of rhenium, tungsten and molybdenum, e.g., containing less than 10 wppm rhenium, less than 1 wppm or less than 0.1 wppm of such metals, individually or collectively. More preferably, the third metal is selected from cobalt, palladium, and ruthenium. When present, the total weight of the third metal preferably is from 0.05 wt. % and 4 wt. %, e.g., from 0.1 wt. % to 3 wt. %, or from 0.1 wt. % to 2 wt. %. 
     In addition to one or more metals, the exemplary catalysts further comprise a support or a modified support, meaning a support that includes a support material and a support modifier, which adjusts the acidity of the support material. The total weight of the support or modified support, based on the total weight of the catalyst, preferably is from 75 wt. % to 99.9 wt. %, e.g., from 78 wt. % to 97 wt. %, or from 80 wt. % to 95 wt. %. In preferred embodiments that use a modified support, the support modifier is present in an amount from 0.1 wt. % to 50 wt. %, e.g., from 0.2 wt. % to 25 wt. %, from 0.5 wt. % to 15 wt. %, or from 1 wt. % to 8 wt. %, based on the total weight of the catalyst. 
     Suitable support materials may include, for example, stable metal oxide-based supports or ceramic-based supports. Preferred supports include silicaceous supports, such as silica, silica/alumina, a Group IIA silicate such as calcium metasilicate, pyrogenic silica, high purity silica, and mixtures thereof. Other supports may include, but are not limited to, iron oxide, alumina, titania, zirconia, magnesium oxide, carbon, graphite, high surface area graphitized carbon, activated carbons, and mixtures thereof. 
     In the production of ethanol, the catalyst support may be modified with a support modifier. Preferably, the support modifier is a basic modifier that has a low volatility or no volatility. Such basic modifiers, for example, may be selected from the group consisting of: (i) alkaline earth oxides, (ii) alkali metal oxides, (iii) alkaline earth metal metasilicates, (iv) alkali metal metasilicates, (v) Group IIB metal oxides, (vi) Group IIB metal metasilicates, (vii) Group IIIB metal oxides, (viii) Group IIIB metal metasilicates, and mixtures thereof. In addition to oxides and metasilicates, other types of modifiers including nitrates, nitrites, acetates, and lactates may be used. Preferably, the support modifier is selected from the group consisting of oxides and metasilicates of any of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc, as well as mixtures of any of the foregoing. Preferably, the support modifier is a calcium silicate, and more preferably calcium metasilicate (CaSiO 3 ). If the support modifier comprises calcium metasilicate, it is preferred that at least a portion of the calcium metasilicate is in crystalline form. 
     A preferred silica support material is SS61138 High Surface Area (HSA) Silica Catalyst Carrier from Saint Gobain N or Pro. The Saint-Gobain N or Pro SS61138 silica contains approximately 95 wt. % high surface area silica; a surface area of about 250 m 2 /g; a median pore diameter of about 12 nm; an average pore volume of about 1.0 cm 3 /g as measured by mercury intrusion porosimetry and a packing density of about 0.352 g/cm 3  (22 lb/ft 3 ). 
     A preferred silica/alumina support material is KA-160 (Sud Chemie) silica spheres having a nominal diameter of about 5 mm, a density of about 0.562 g/ml, in absorptivity of about 0.583 g H 2 O/g support, a surface area of about 160 to 175 m 2 /g, and a pore volume of about 0.68 ml/g. 
     As will be appreciated by those of ordinary skill in the art, support materials are selected such that the catalyst system is suitably active, selective and robust under the process conditions employed for the formation of ethanol. 
     The metals of the catalysts may be dispersed throughout the support, coated on the outer surface of the support (egg shell) or decorated on the surface of the support. 
     The catalyst compositions suitable for use with the present invention preferably are formed through metal impregnation of the modified support, although other processes such as chemical vapor deposition may also be employed. Such impregnation techniques are described in U.S. Pat. No. 7,608,744, U.S. Publication No. 2010/0029995, and U.S. application Ser. No. 12/698,968, referred to above, the entireties of which are incorporated herein by reference. 
     Some embodiments of the process of hydrogenating a mixed acid feed to form ethanol and one or more higher alcohols according to one embodiment of the invention may include a variety of configurations using a fixed bed reactor or a fluidized bed reactor, as one of skill in the art will readily appreciate. In many embodiments of the present invention, an “adiabatic” reactor can be used; that is, there is little or no need for internal plumbing through the reaction zone to add or remove heat. In other embodiments, radial flow reactor or reactors may be employed, or a series of reactors may be employed with or with out heat exchange, quenching, or introduction of additional feed material. Alternatively, a shell and tube reactor provided with a heat transfer medium may be used. In many cases, the reaction zone may be housed in a single vessel or in a series of vessels with heat exchangers therebetween. 
     In preferred embodiments, the catalyst is employed in a fixed bed reactor, e.g., in the shape of a pipe or tube, where the reactants, typically in the vapor form, are passed over or through the catalyst. Other reactors, such as fluid or ebullient bed reactors, can be employed. In some instances, the hydrogenation catalysts may be used in conjunction with an inert material to regulate the pressure drop of the reactant stream through the catalyst bed and the contact time of the reactant compounds with the catalyst particles. 
     The hydrogenation reaction may be carried out in either the liquid phase or vapor phase. Preferably, the reaction is carried out in the vapor phase under the following conditions. The reaction temperature may range from 125° C. to 350° C., e.g., from 200° C. to 325° C., from 225° C. to 300° C., or from 250° C. to 300° C. The pressure may range from 10 KPa to 3000 KPa (about 1.5 to 435 psi), e.g., from 50 KPa to 2300 KPa, or from 100 KPa to 1500 KPa. The reactants may be fed to the reactor at a gas hourly space velocity (GHSV) of greater than 500 hr −1 , e.g., greater than 1000 hr −1 , greater than 2500 hr −1  or even greater than 5000 hr −1 . In terms of ranges the GHSV may range from 50 hr −1  to 50,000 hr −1 , e.g., from 500 hr −1  to 30,000 hr −1 , from 1000 hr −1  to 10,000 hr −1 , or from 1000 hr −1  to 6500 hr −1 . 
     The hydrogenation optionally is carried out at a pressure just sufficient to overcome the pressure drop across the catalytic bed at the GHSV selected, although there is no bar to the use of higher pressures, it being understood that considerable pressure drop through the reactor bed may be experienced at high space velocities, e.g., 5000 hr −1  or 6,500 hr −1 . 
     Although the reaction consumes two moles of hydrogen per mole of acid to produce one mole of ethanol (or higher alcohol for the higher acids), the actual molar ratio of hydrogen to total acid (including acetic acid and higher acid) in the feed stream may vary from about 100:1 to 1:100, e.g., from 50:1 to 1:50, from 20:1 to 1:2, or from 12:1 to 1:1. Most preferably, the molar ratio of hydrogen to total acid is greater than 2:1, e.g., greater than 4:1 or greater than 8:1. 
     Contact or residence time can also vary widely, depending upon such variables as amount of acetic acid, amount of higher acid, catalyst, reactor, temperature and pressure. Typical contact times range from a fraction of a second to more than several hours when a catalyst system other than a fixed bed is used, with preferred contact times, at least for vapor phase reactions, of from 0.1 to 100 seconds, e.g., from 0.3 to 80 seconds or from 0.4 to 30 seconds. 
     The raw materials, acetic acid, the higher acid and hydrogen, used in connection with the process of this invention may be derived from any suitable source including natural gas, petroleum, coal, biomass, and so forth. As examples, acetic acid may be produced via methanol carbonylation, acetaldehyde oxidation, ethylene oxidation, oxidative fermentation, and anaerobic fermentation. The higher acid, in particular propionic acid, may be formed as a byproduct of the carbonylation process, particularly in the Cativa™ process for producing acetic acid, as described in J. Jones et al.,  Platinum Metals Review , Vol. 44, No. 3, pp. 94-104 (July 2000) and U.S. Pat. No. 6,140,535, the entireties of which are incorporated herein by reference. Alternatively, the higher acid may be separately synthesized, e.g., in the carbonylation of ethanol to make propionic acid. As petroleum and natural gas prices fluctuate, becoming either more or less expensive, methods for producing acetic acid and intermediates such as methanol and carbon monoxide from alternate carbon sources have drawn increasing interest. In particular, when petroleum is relatively expensive compared to natural gas, it may become advantageous to produce acetic acid from synthesis gas (“syn gas”) that is derived from any available carbon source. U.S. Pat. No. 6,232,352, the disclosure of which is incorporated herein by reference, for example, teaches a method of retrofitting a methanol plant for the manufacture of acetic acid. By retrofitting a methanol plant, the large capital costs associated with carbon monoxide generation for a new acetic acid plant are significantly reduced or largely eliminated. All or part of the syn gas is diverted from the methanol synthesis loop and supplied to a separator unit to recover carbon monoxide and hydrogen, which are then used to produce acetic acid and optionally the higher acid. In addition to acids, such a process can also be used to make hydrogen which may be utilized in connection with this invention. 
     Methanol carbonylation processes suitable for production of acetic acid are described in U.S. Pat. Nos. 7,208,624, 7,115,772, 7,005,541, 6,657,078, 6,627,770, 6,143,930, 5,599,976, 5,144,068, 5,026,908, 5,001,259, and 4,994,608, the disclosures of which are incorporated herein by reference. Optionally, the production of ethanol may be integrated with such methanol carbonylation processes. 
     U.S. Pat. No. RE 35,377 also incorporated herein by reference, provides a method for the production of methanol by conversion of carbonaceous materials such as oil, coal, natural gas and biomass materials. The process includes hydrogasification of solid and/or liquid carbonaceous materials to obtain a process gas which is steam pyrolized with additional natural gas to form synthesis gas. The syn gas is converted to methanol which may be carbonylated to acetic acid. The method likewise produces hydrogen which may be used in connection with this invention as noted above. U.S. Pat. No. 5,821,111, which discloses a process for converting waste biomass through gasification into synthesis gas as well as U.S. Pat. No. 6,685,754, the disclosures of which are incorporated herein by reference. 
     As indicated above, the feed stream that is fed to the hydrogenation reaction comprises acetic acid and one or more higher acids, e.g., propionic acid. For example, the acid feed stream may comprise a higher acid, e.g., such as propionic acid, in an amount greater than 0.01 wt. %, e.g., greater than 0.04 wt. %, greater than 0.08 wt. %, greater than 1 wt. %, greater than 2 wt. % or greater than 5 wt. %. In terms of ranges, the mixed acid feed stream may comprise the higher acid in an amount from 0.001 wt. % to 40 wt. %, e.g., from 0.01 wt. % 20 wt. %, from 0.04 wt. % to 20 wt. %, from 0.5 to 10 wt. %, from 1 to 8 wt. % or from 2 to 5 wt. %, or in other embodiments, in an amount ranging from 0.001 wt. % to 20 wt. %, e.g., from 0.001 wt. % to 15 wt. %, from 0.01 wt. % to 14 wt. %, from 0.13 wt. % to 13.2 wt. %, from 1.3 wt. % to 11.9 wt. %, or from 4 wt. % to 9.3 wt. %. In some exemplary embodiments, the molar ratio of acetic acid to the higher acids (collectively) in the feed stream ranges from 1:1 to 10,000:1, e.g., from 1:1 to 1000:1, from 1:1 to 200:1, from 2:1 to 150:1, from 10:1 to 120:1 or from 50:1 to 100:1. The feed stream may also comprise esters and/or anhydrides as well as acetaldehyde and acetone. Thus, the feed stream may be a cruder acetic acid feed stream, e.g., a less-refined acetic acid feed stream. In these embodiments, the propionic acid in the acetic acid feed stream is hydrogenated to form n-propanol, which may serve as a denaturant (e.g., for non-fuel uses). The n-propanol may be present in the resulting mixed alcohol composition in an amount ranging from 0.001 wt. % to 40 wt. %, e.g., from 0.01 wt. % 20 wt. %, from 0.04 wt. % to 20 wt. %, from 0.5 to 10 wt. %, from 1 to 8 wt. % or from 2 to 5 wt. %., or in other embodiments, in an amount ranging from 0.001 wt. % to 20 wt. %, e.g., from 0.001 wt. % to 15 wt. %, from 0.01 wt. % to 14 wt. %, from 0.13 wt. % to 13.2 wt. %, from 1.3 wt. % to 11.9 wt. %, or from 4 wt. % to 9.3 wt. %. 
     Alternatively, acetic acid and higher acids in vapor form may be taken directly as crude product from the flash vessel of a methanol carbonylation unit of the class described in U.S. Pat. No. 6,657,078, the entirety of which is incorporated herein by reference. The crude vapor product, for example, may be fed directly to the ethanol synthesis reaction zones of the present invention without the need for condensing the acetic acid, the higher acid and light ends or removing water, saving overall processing costs. 
     In one embodiment, acetone is added to the reactor as a reactant in addition to the acetic acid, the higher acid and hydrogen. Without being bound by theory, it is believed that the addition of acetone to the reaction provides for the production of isopropanol, which may serve as a denaturant (e.g., for non-fuel uses) or enhance blending ability for fuel uses. In another aspect, acetone is formed as a by-product of the hydrogenation of acetic acid and the higher acid. Once formed, the acetone may be hydrogenated to form isopropanol. In some embodiments, where the presence of isopropanol is desired, e.g., as a denaturant, separate catalysts may be utilized to yield a higher concentration of acetone, which, upon subsequent hydrogenation, would result in a higher concentration of isopropanol in the crude ethanol composition. As an example, a catalyst composition comprising a support such as TiO 2 , ZrO 2 , Fe 2 O 3 , or CeO 2  may be used. Other exemplary catalyst compositions include ruthenium supported by SiO 2 , iron supported by carbon, or palladium supported by carbon. 
     In one embodiment, the acetone is formed in an auxiliary reaction performed in an auxiliary acetone reactor. As an example, acetic acid and optionally the higher acid may be reacted in the auxiliary reactor under conditions effective to form acetone, e.g., ketonization. The acetic acid and optional higher acid fed to the auxiliary reactor may be drawn from the mixed acid feed stream fed to the hydrogenation reactor. The auxiliary reactor may be of the types discussed above. For example, the auxiliary reactor may be a fixed bed reactor that has a catalyst disposed therein. Preferably, the auxiliary reactor is in the shape of a pipe or tube, where the reactants, typically in the vapor form, are passed over or through the catalyst, which is disposed in the pipe or tube. In some embodiments, the auxiliary reactor utilizes a catalyst that promotes ketonization and/or favors the production of acetone. As an example, the catalyst may comprise a basic catalyst, e.g., thorium oxide. In some embodiments, the acetone yielded by the auxiliary reactor is directed to the hydrogenation reactor as a reactant in addition to the acetic acid, the higher acid and the hydrogen. 
     The acetic acid and the higher acid may be vaporized at the reaction temperature, following which the vaporized mixed acid feed can be fed along with hydrogen in an undiluted state or diluted with a relatively inert carrier gas, such as nitrogen, argon, helium, carbon dioxide and the like. For reactions run in the vapor phase, the temperature should be controlled in the system such that it does not fall below the dew point of acetic acid or the higher acid. In one embodiment the acid may be vaporized at the boiling point of the acid at the particular pressure, and then the vaporized acid may be further heated to the reactor inlet temperature. In another embodiment, the acetic acid and the heavier acid are transferred to the vapor state by passing hydrogen, recycle gas, another suitable gas, or mixtures thereof through the mixed acid feed at a temperature below the boiling point of the acids, thereby humidifying the carrier gas with acetic acid and heavier acid vapors, followed by heating the mixed vapors up to the reactor inlet temperature. Preferably, the acetic acid and the heavier acid are transferred to the vapor by passing hydrogen and/or recycle gas through the mixed acid feed at a temperature at or below 125° C., followed by heating of the combined gaseous stream to the reactor inlet temperature. 
     In particular, the hydrogenation of the acetic acid may achieve favorable conversion of acetic acid and favorable selectivity and productivity to ethanol. Similarly, the hydrogenation of higher acids may achieve favorable conversion, selectivity and productivity to higher alcohols. For purposes of the present invention, the term “conversion” refers to the amount of acetic acid in the feed that is converted to a compound other than acetic acid. Conversion is expressed as a mole percentage based on specified acid in the feed. The conversion may be at least 10%, e.g., at least 20%, at least 40%, at least 50%, at least 60%, at least 70% or at least 80%. Although catalysts that have high conversions are desirable, such as at least 80% or at least 90%, in some embodiments a low conversion may be acceptable at high selectivity for ethanol. It is, of course, well understood that in many cases, it is possible to compensate for conversion by appropriate recycle streams or use of larger reactors, but it is more difficult to compensate for poor selectivity. 
     Selectivity is expressed as a mole percent based on the converted acid. It should be understood that each compound converted from the specified acid has an independent selectivity and that selectivity is independent from conversion. For example, if 50 mole % of the converted acetic acid is converted to ethanol, we refer to the ethanol selectivity as 50%. Preferably, the catalyst selectivity to ethoxylates is at least 60%, e.g., at least 70%, or at least 80%. As used herein, the term “ethoxylates” refers specifically to the compounds ethanol, acetaldehyde, and ethyl acetate. Preferably, the selectivity of acetic acid to ethanol is at least 80%, e.g., at least 85% or at least 88%. Similar selectivities may be achieved for the higher acid to the higher alcohol. Preferred embodiments of the hydrogenation process also have low selectivity to undesirable products, such as methane, ethane, and carbon dioxide. The selectivity to these undesirable products preferably is less than 4%, e.g., less than 2% or less than 1%. More preferably, these undesirable products are not detectable. Formation of alkanes may be low, and ideally less than 2%, less than 1%, or less than 0.5% of the acetic acid and higher acid passed over the catalyst is converted to alkanes, which have little value other than as fuel. 
     The term “productivity,” as used herein, refers to the grams of a specified product, e.g., ethanol, formed during the hydrogenation based on the kilograms of catalyst used per hour. A productivity of at least 200 grams of ethanol per kilogram catalyst per hour, e.g., at least 400 grams of ethanol per kilogram catalyst per hour or at least 600 grams of ethanol per kilogram catalyst per hour, is preferred. In terms of ranges, the productivity preferably is from 200 to 3,000 grams of ethanol per kilogram catalyst per hour, e.g., from 400 to 2,500 per kilogram catalyst per hour or from 600 to 2,000 per kilogram catalyst per hour. 
     In various embodiments, the crude ethanol product produced by the hydrogenation process, before any subsequent processing, such as purification and separation, will typically comprise unreacted acetic acid, unreacted higher acid, ethanol, one or more higher alcohols, and water. As used herein, the term “crude alcohol product” refers to any composition comprising from 5 wt. % to 70 wt. % ethanol and higher alcohols and from 5 wt. % to 35 wt. % water. In some exemplary embodiments, the crude alcohol product comprises ethanol and higher alcohols in an amount from 5 wt. % to 70 wt. %, e.g., from 10 wt. % to 60 wt. %, or from 15 wt. % to 50 wt. %, based on the total weight of the crude ethanol product. Preferably, the crude ethanol product comprises at least 10 wt. % ethanol, at least 15 wt. % ethanol, or at least 20 wt. % ethanol. The crude alcohol product preferably comprises the higher alcohol or alcohols in an amount greater than 0.01 wt. %, e.g., greater than 0.04 wt. %, greater than 0.5 wt. %, greater than 0.8 wt. %, greater than 1 wt. %, greater than 2 wt. %, greater than 3 wt. % or greater than 5 wt. %. In terms of ranges, the crude alcohol product optionally comprises the higher alcohol or alcohols in an amount from 0.01 to 20 wt. %, e.g., from 0.04 to 20 wt. %, from 0.5 to 10 wt. %, from 1 to 8 wt. % or from 2 to 5 wt. %. In some exemplary embodiments, the molar ratio of ethanol to the higher alcohol in the crude alcohol product optionally ranges from 1:1 to 1000:1, e.g., from 1:1 to 200:1, from 2:1 to 150:1, from 10:1 to 120:1 or from 50:1 to 100:1. 
     The crude alcohol product typically will further comprise unreacted acetic acid and unreacted higher acid, depending on conversion, for example, in an amount of less than 90 wt. %, e.g., less than 80 wt. % or less than 70 wt. %. In terms of ranges, the unreacted acetic acid and unreacted higher acid is optionally present in amounts from 0 to 90 wt. %, e.g., from 5 wt. % to 80 wt. %, from 15 wt. % to 70 wt. %, from 20 wt. % to 70 wt. % or from 25 wt. % to 65 wt. %. Where acetone is included as a reactant, the crude alcohol product may comprise from 0.01 wt. % to 10 wt. % isopropanol, e.g., from 0.1 wt. % to 10 wt %, from 1 wt. % to 9 wt. % or from 3 wt. % to 7 wt. %. In other embodiments, the crude alcohol product comprises from 0.01 wt. % to 20 wt. % diethyl ether, e.g., from 0.1 wt. % to 10 wt. %, from 1 wt. % to 9 wt. % or from 3 wt. % to 7 wt. %. As water is formed in the reaction process, the crude alcohol product will generally comprise water, for example, in amounts ranging from 5 wt. % to 35 wt. %, e.g., from 10 wt. % to 30 wt. % or from 10 wt. % to 26 wt. %. Ethyl acetate and higher esters, e.g., propyl acetate or ethyl propionate, may also be produced during the hydrogenation of acetic acid and higher acids or through side reactions. In these embodiments, the crude alcohol product may comprise esters in an amount ranging from 0 to 20 wt. %, e.g., from 0 to 15 wt. %, from 1 to 12 wt. % or from 3 to 10 wt. %. Acetaldehyde may also be produced through side reactions. Higher esters, such as propyl acetate and ethyl propionate, may be present in an amount from 0.001 to 5 wt. %, e.g., from 0.01 to 3 wt. % or from 0.1 to 1 wt. %. In these embodiments, the crude alcohol product comprises acetaldehyde in amounts ranging from 0 to 10 wt. %, e.g., from 0 to 3 wt. %, from 0.1 to 3 wt. % or from 0.2 to 2 wt. %. In some embodiments, where propionic acid is included as a reactant, the n-propanol formed via hydrogenation may be present in the crude alcohol product in an amount ranging from 0.001 wt. % to 40 wt. %, e.g., from 0.01 wt. % 20 wt. %, from 0.04 wt. % to 20 wt. %, from 0.5 to 10 wt. %, from 1 to 8 wt. % or from 2 to 5 wt. %, or in other embodiments, in an amount ranging from 0.001 wt. % to 20 wt. %, e.g., from 0.001 wt. % to 15 wt. %, from 0.01 wt. % to 14 wt. %, from 0.13 wt. % to 13.2 wt. %, from 1.3 wt. % to 11.9 wt. %, or from 4 wt. % to 9.3 wt. %. 
     Thus, the hydrogenation reaction produces a crude alcohol product that may comprise, inter alia, denaturants such as n-propanol, isopropanol, alkyl acetates such as ethyl acetate, diethyl ether, and/or acetaldehyde. Each of these in situ-formed compounds, alone or in combination with one another, may serve as a denaturant in a denatured ethanol composition. In some embodiments, all or a portion of the crude alcohol product may be combined with a purified ethanol stream to form a denatured ethanol composition. It is within the scope of the invention to adjust the reaction parameters to achieve desired crude alcohol product and, thus, a desired denatured ethanol composition. In one embodiment, the amount of reactants, e.g., acetic acid, higher acid (e.g., propionic acid), acetone, etc., fed to the hydrogenation reactor may be adjusted so as to achieve a specific amount of one or more components, e.g., denaturants, in the crude alcohol product. The denaturant, thus produced, may be combined with a purified ethanol stream to form a denatured ethanol composition. For example, a denatured ethanol composition comprising about 5 parts isopropanol to 100 parts ethanol, may be produced by feeding an acetic acid stream comprising acetic acid and acetone. As another example, a denatured ethanol composition comprising about 5 parts n-propanol to 100 parts ethanol, may be produced by feeding an acetic acid stream comprising acetic acid and propionic acid. It is further within the scope of the invention to adjust additional hydrogenation reactor parameters to achieve a crude alcohol product comprising a desired amount of a particular denaturant or combination of denaturants. For example, in order to produce a crude alcohol product comprising about 10 parts diethyl ether, a hydrogenation catalyst having an acidic support may be utilized as described in co-pending U.S. application Ser. No. 12/850,414, entitled “Processes for Making Diethyl Ether from Acetic Acid,” filed on Aug. 4, 2010, the entire contents and disclosure of which is hereby incorporated by reference. 
     In one embodiment, because it is difficult to separate propanol, e.g., isopropanol or n-propanol, and ethanol from one another, all or a portion of the propanol formed in the hydrogenation reaction may follow the ethanol through the separation scheme. Because the crude ethanol composition, as formed, may contain in situ-formed denaturant(s), at least a portion of the crude ethanol composition, with or without further separation, may be combined with a purified ethanol stream to form a denatured ethanol composition. In one embodiment, one or more of the in situ-formed denaturants may be separated from the crude alcohol product and combined with a purified ethanol stream. In other embodiments, at least a portion, e.g., an aliquot portion, of the crude alcohol product may be combined with a purified ethanol stream. For example, when the crude alcohol product comprises n-propanol, at least a portion of an n-propanol-containing crude alcohol product may be combined with a purified ethanol stream to form a denatured ethanol composition comprising an n-propanol denaturant. In another embodiment, at least a portion of the n-propanol is separated from the crude alcohol product and combined with a purified ethanol stream to form an n-propanol denatured ethanol composition. 
     Other components, such as, for example, esters, ethers, aldehydes, ketones, alkanes, and carbon dioxide, if detectable, collectively may be present in amounts less than 10 wt. %, e.g., less than 6 wt. %, or less than 4 wt. %. In terms of ranges, the crude alcohol product composition may comprise the other components in an amount from 0.1 wt. % to 10 wt. %, e.g., from 0.1 wt. % to 6 wt. %, or from 0.1 wt. % to 4 wt. %. Exemplary crude alcohol product compositional ranges are provided in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 CRUDE ALCOHOL PRODUCT COMPOSITIONS 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Conc. 
                 Conc. 
                 Conc. 
                 Conc. 
               
               
                 Component 
                 (wt. %) 
                 (wt. %) 
                 (wt. %) 
                 (wt. %) 
               
               
                   
               
               
                 Ethanol 
                 5 to 70 
                 10 to 60  
                 15 to 50 
                 25 to 50 
               
               
                 Acetic Acid 
                 0 to 90 
                 5 to 80 
                 15 to 70 
                 20 to 70 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.04 to 20   
                 1 to 8 
                 2 to 5 
               
               
                 Higher Acid** 
                 &lt;20 
                 0.04 to 20   
                 1 to 8 
                 2 to 5 
               
               
                 Water 
                 5 to 35 
                 5 to 30 
                 10 to 30 
                 10 to 26 
               
               
                 Ethyl Acetate 
                 0 to 20 
                 0 to 15 
                  1 to 12 
                  3 to 10 
               
               
                 Acetaldehyde 
                 0 to 10 
                 0 to 3  
                 0.1 to 3   
                 0.2 to 2   
               
               
                 Others 
                 0.1 to 10   
                 0.1 to 6   
                 0.1 to 4   
                 — 
               
               
                   
               
               
                 *preferably propanol (n-propanol, isopropanol or both). 
               
               
                 **preferably propionic acid. 
               
            
           
         
       
     
     In one embodiment, the crude ethanol product may comprise acetic acid in an amount less than 20 wt. %, e.g., less than 15 wt. %, less than 10 wt. % or less than 5 wt. %. In embodiments having lower amounts of acetic acid, the conversion of acetic acid is preferably greater than 75%, e.g., greater than 85% or greater than 90%. In addition, the selectivity to ethanol may also be preferably high, and is preferably greater than 75%, e.g., greater than 85% or greater than 90%. 
     As shown in Table 1, in some embodiments the crude alcohol product may be a denatured ethanol composition. For example, the crude ethanol composition may comprise ethanol and at least one denaturant, which preferably comprises one or more higher alcohols, preferably propanol. In other aspects, in addition to or as an alternative to the higher alcohol(s), acetic acid, ethyl acetate, or acetaldehyde may be the denaturant. In other embodiments, the crude ethanol composition may be a denatured ethanol composition comprising at least one of the denaturants discussed above. 
     Purification 
       FIG. 1A  shows a hydrogenation system  100  suitable for the hydrogenation of acetic acid and higher acids and separating a mixed alcohol product from the crude reaction mixture according to one embodiment of the invention. System  100  comprises reaction zone  101  and distillation zone  102 . Reaction zone  101  comprises reactor  103 , hydrogen feed line  104  and feed line  105 . As discussed above, a mixed acid feed comprising acetic acid and one or more heavier acids, e.g., propionic acid, is preferably fed to the reaction zone  101 . The acetic acid and the one or more heavier acids may be fed separately or together to the reaction zone. In other embodiments, where acetone utilized as a reactant, reaction zone  101  further comprises an acetone feed line (not shown). In other embodiments, where the heavier acid is fed separately to as a reactant, reaction zone  101  may further comprise a heavier acid feed line, e.g., propionic acid feed line (not shown). 
     Distillation zone  102  comprises flasher  106 , first column  107 , second column  108 , and third column  109 . Hydrogen, acetic acid, the heavier acid(s) and optionally acetone are fed to a vaporizer  110  via lines  104  and  105 , respectively, to create a vapor feed stream in line  111  that is directed to reactor  103 . In one embodiment, lines  104  and  105  may be combined and jointly fed to the vaporizer  110 , e.g., in one stream containing both hydrogen, acetic acid and the heavier acid. The temperature of the vapor feed stream in line  111  is preferably from 100° C. to 350° C., e.g., from 120° C. to 310° C. or from 150° C. to 300° C. Any feed that is not vaporized is removed from vaporizer  110 , as shown in  FIG. 1A , and may be recycled thereto. In addition, although  FIG. 1A  shows line  111  being directed to the top of reactor  103 , line  111  may be directed to the side, upper portion, or bottom of reactor  103 . Although one reactor and one flasher are shown in  FIGS. 1A ,  1 B and  1 C, additional reactors and/or components may be included in various optional embodiments of the present invention. For example, the hydrogenation system may optionally comprise dual reactors, dual flashers, heat exchanger(s), and/or pre-heater(s). 
     Reactor  103  contains the catalyst that is used in the hydrogenation of the carboxylic acid, preferably acetic acid and the heavier acid. In some embodiment where acetone is a reactant and isopropanol is a desired co-product with ethanol, the catalyst in reactor  103  is selected such that, in addition to ethanol, isopropanol is also produced, optionally in addition to one or more higher alcohols. As an example, a catalyst composition comprising a support such as TiO 2 , ZrO 2 , Fe 2 O 3 , or CeO 2  may be used. In some embodiments, these catalysts promote higher acetone formation. Other exemplary catalyst compositions include ruthenium supported by SiO 2 , iron supported by carbon, or palladium supported by carbon. In other embodiments, the temperature of reactor  103  may be adjusted to achieve a desired higher alcohol, e.g., propanol, concentration. For example, maintaining the reaction temperature in a range of 200° C. to 350° C., e.g., from 225° C. to 300° C., may lead to an ethanol composition comprising from 0.1 wt. % to 10 wt. % isopropanol, e.g., from 1 wt. % to 9 wt. % or from 3 wt. % to 7 wt. %. In one embodiment, one or more guard beds (not shown) may be used to protect the catalyst from poisons or undesirable impurities contained in the feed or return/recycle streams. Such guard beds may be employed in the vapor or liquid streams. Suitable guard bed materials are known in the art and include, for example, carbon, silica, alumina, ceramic, or resins. In one aspect, the guard bed media is functionalized to trap particular species such as sulfur or halogens. During the hydrogenation process, a crude alcohol product stream is withdrawn, preferably continuously, from reactor  103  via line  112 . The crude alcohol product stream may be condensed and fed to flasher  106 , which, in turn, provides a vapor stream and a liquid stream. The flasher  106  in one embodiment preferably operates at a temperature of from 50° C. to 500° C., e.g., from 70° C. to 400° C. or from 100° C. to 350° C. In one embodiment, the pressure of flasher  106  preferably is from 50 KPa to 2000 KPa, e.g., from 75 KPa to 1500 KPa or from 100 to 1000 KPa. In one preferred embodiment, the temperature and pressure of flasher  106  is similar to the temperature and pressure of reactor  103 . 
     The vapor stream exiting the flasher  106  may comprise hydrogen and hydrocarbons, which may be purged and/or returned to reaction zone  101  via line  113 . As shown in  FIG. 1A , the returned portion of the vapor stream passes through compressor  114  and is combined with the hydrogen feed and co-fed to vaporizer  110 . 
     The liquid from flasher  106  is withdrawn and pumped as a feed composition via line  115  to the side of first column  107 , also referred to as the acid separation column. The contents of line  115  typically will be substantially similar to the product obtained directly from the reactor, and may, in fact, also be characterized as a crude alcohol product. However, the feed composition in line  115  preferably has substantially no hydrogen, carbon dioxide, methane or ethane, which are removed by flasher  106 . Exemplary components of liquid in line  115  are provided in Table 2. It should be understood that liquid line  115  may contain other components, not listed, such as components in the feed. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 FEED COMPOSITION TO FIRST DISTILLATION COLUMN 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Ethanol 
                 5 to 70 
                   10 to 60 
                 15 to 50 
               
               
                 Higher Alcohols* 
                 0.01 to 20   
                 0.04 to 20 
                 0.5 to 10  
               
               
                 Water 
                 5 to 35 
                   5 to 30 
                 10 to 30 
               
               
                 Acetic Acid 
                 &lt;90 
                   5 to 80 
                 15 to 70 
               
               
                 Ethyl Acetate 
                 &lt;20 
                 0.001 to 15  
                  1 to 12 
               
               
                 Acetaldehyde 
                 &lt;10 
                 0.001 to 3  
                 0.1 to 3   
               
               
                 Acetal 
                 &lt;5 
                 0.001 to 2  
                 0.005 to 1    
               
               
                 Acetone 
                 &lt;5 
                 0.0005 to 0.05  
                 0.001 to 0.03  
               
               
                 Other Esters 
                 &lt;5 
                 &lt;0.005 
                 &lt;0.001 
               
               
                 Other Ethers 
                 &lt;5 
                 &lt;0.005 
                 &lt;0.001 
               
               
                   
               
            
           
         
       
     
     The amounts indicated as less than (&lt;) in the tables throughout the present application are preferably not present and if present may be present in trace amounts or in amounts greater than 0.0001 wt. %. 
     The “other esters” in Table 2 may include, but are not limited to, ethyl propionate, methyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate or mixtures thereof. The “other ethers” in Table 2 may include, but are not limited to, diethyl ether, methyl ethyl ether, isobutyl ethyl ether or mixtures thereof. The “higher alcohols” in Table 2 may include, but are not limited to, isopropanol, n-propanol, n-butanol or mixtures thereof. 
     When the acid content in line  115  is less than 5 wt. %, the acid separation column  107  may be skipped and line  115  may be introduced directly to second column  108 , also referred to herein as a light ends column. 
     In the embodiment shown in  FIG. 1A , line  115  is introduced in the lower part of first column  107 , e.g., lower half or lower third. In first column  107 , unreacted acids, a portion of the water, and other heavy components, if present, are removed from the composition in line  115  and are withdrawn, preferably continuously, as residue. Some or all of the residue may be returned and/or recycled back to reaction zone  101  via line  116 . First column  107  also forms an overhead distillate, which is withdrawn in line  117 , and which may be condensed and refluxed, for example, at a ratio of from 10:1 to 1:10, e.g., from 3:1 to 1:3 or from 1:2 to 2:1. 
     Any of columns  107 ,  108  or  109  may comprise any distillation column capable of separation and/or purification. The columns preferably comprise tray columns having from 1 to 150 trays, e.g., from 10 to 100 trays, from 20 to 95 trays or from 30 to 75 trays. The trays may be sieve trays, fixed valve trays, movable valve trays, or any other suitable design known in the art. In other embodiments, a packed column may be used. For packed columns, structured packing or random packing may be employed. The trays or packing may be arranged in one continuous column or they may be arranged in two or more columns such that the vapor from the first section enters the second section while the liquid from the second section enters the first section, etc. 
     The associated condensers and liquid separation vessels that may be employed with each of the distillation columns may be of any conventional design and are simplified in  FIGS. 1A ,  1 B, and  1 C. As shown in  FIGS. 1A ,  1 B, and  1 C, heat may be supplied to the base of each column or to a circulating bottom stream through a heat exchanger or reboiler. Other types of reboilers, such as internal reboilers, may also be used in some embodiments. The heat that is provided to reboilers may be derived from any heat generated during the process that is integrated with the reboilers or from an external source such as another heat generating chemical process or a boiler. Although one reactor and one flasher are shown in  FIGS. 1A ,  1 B, and  1 C, additional reactors, flashers, condensers, heating elements, and other components may be used in embodiments of the present invention. As will be recognized by those skilled in the art, various condensers, pumps, compressors, reboilers, drums, valves, connectors, separation vessels, etc., normally employed in carrying out chemical processes may also be combined and employed in the processes of the present invention. 
     The temperatures and pressures employed in any of the columns may vary. As a practical matter, pressures from 10 kPa to 3000 kPa will generally be employed in these zones although in some embodiments subatmospheric pressures may be employed as well as superatmospheric pressures. Temperatures within the various zones will normally range between the boiling points of the composition removed as the distillate and the composition removed as the residue. It will be recognized by those skilled in the art that the temperature at a given location in an operating distillation column is dependant on the composition of the material at that location and the pressure of column. In addition, feed rates may vary depending on the size of the production process and, if described, may be generically referred to in terms of feed weight ratios. 
     When column  107  is operated under standard atmospheric pressure, the temperature of the residue exiting in line  116  from column  107  preferably is from 95° C. to 120° C., e.g., from 105° C. to 117° C. or from 110° C. to 115° C. The temperature of the distillate exiting in line  117  from column  107  preferably is from 70° C. to 110° C., e.g., from 75° C. to 95° C. or from 80° C. to 90° C. In other embodiments, the pressure of first column  107  may range from 0.1 kPa to 510 kPa, e.g., from 1 kPa to 475 kPa or from 1 kPa to 375 kPa. Exemplary components of the distillate and residue compositions for first column  107  are provided in Table 3 below. It should also be understood that the distillate and residue may also contain other components, not listed, such as components in the feed. For convenience, the distillate and residue of the first column may also be referred to as the “first distillate” or “first residue.” The distillates or residues of the other columns may also be referred to with similar numeric modifiers (second, third, etc.) in order to distinguish them from one another, but such modifiers should not be construed as requiring any particular separation order. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 FIRST COLUMN 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Distillate 
                   
                   
                   
               
               
                 Ethanol 
                 20 to 75 
                 30 to 70 
                 40 to 65 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.04 to 20   
                 0.5 to 10  
               
               
                 Water 
                 10 to 40 
                 15 to 35 
                 20 to 35 
               
               
                 Acetic Acid 
                 &lt;2 
                 0.001 to 0.5  
                 0.01 to 0.2  
               
               
                 Ethyl Acetate 
                 &lt;60 
                 5.0 to 40  
                 10 to 30 
               
               
                 Acetaldehyde 
                 &lt;10 
                 0.001 to 5    
                 0.01 to 4   
               
               
                 Diethyl Ether 
                 0.02 to 7.5  
                 0.3 to 6.5 
                 1.2 to 5   
               
               
                 Acetal 
                 &lt;0.1 
                 &lt;0.1 
                 &lt;0.05 
               
               
                 Acetone 
                 &lt;0.05 
                 0.001 to 0.03  
                  0.01 to 0.025 
               
               
                 Residue 
               
               
                 Acetic Acid 
                  60 to 100 
                 70 to 95 
                 85 to 92 
               
               
                 Higher Acid** 
                 0.01 to 20   
                 0.04 to 20   
                 0.5 to 10  
               
               
                 Water 
                 &lt;30 
                  1 to 20 
                  1 to 15 
               
               
                 Ethanol 
                 &lt;1 
                 &lt;0.9 
                 &lt;0.07 
               
               
                   
               
            
           
         
       
     
     As shown in Table 3, without being bound by theory, it has surprisingly and unexpectedly been discovered that when any amount of acetal is detected in the feed that is introduced to the acid separation column (first column  107 ), the acetal appears to decompose in the column such that less or even no detectable amounts are present in the distillate and/or residue. 
     Depending on the reaction conditions, the crude alcohol product exiting reactor  103  in line  112  may comprise ethanol, higher alcohol, acetic acid (unconverted), higher acid (unconverted), ethyl acetate, and water. After exiting reactor  103 , a non-catalyzed equilibrium reaction may occur between the components contained in the crude alcohol product until it is added to flasher  106  and/or first column  107 . This equilibrium reaction tends to drive the crude alcohol product to an equilibrium between ethanol/acetic acid and ethyl acetate/water, as shown below. Similar equilibria exist for the higher acids and higher alcohols. 
       EtOH+HOAc⇄EtOAc+H 2 O
 
     In the event the crude alcohol product is temporarily stored, e.g., in a holding tank, prior to being directed to distillation zone  102 , extended residence times may be encountered. Generally, the longer the residence time between reaction zone  101  and distillation zone  102 , the greater the formation of ethyl acetate. For example, when the residence time between reaction zone  101  and distillation zone  102  is greater than 5 days, significantly more ethyl acetate may form at the expense of ethanol. Thus, shorter residence times between reaction zone  101  and distillation zone  102  are generally preferred in order to maximize the amount of ethanol formed. In one embodiment, a holding tank (not shown), is included between the reaction zone  101  and distillation zone  102  for temporarily storing the liquid component from line  115  for up to 5 days, e.g., up to 1 day, or up to 1 hour. In a preferred embodiment no tank is included and the condensed liquids are fed directly to the first distillation column  107 . In addition, the rate at which the non-catalyzed reaction occurs may increase as the temperature of the crude alcohol product, e.g., in line  115 , increases. These reaction rates may be particularly problematic at temperatures exceeding 30° C., e.g., exceeding 40° C. or exceeding 50° C. Thus, in one embodiment, the temperature of liquid components in line  115  or in the optional holding tank is maintained at a temperature less than 40° C., e.g., less than 30° C. or less than 20° C. One or more cooling devices may be used to reduce the temperature of the liquid in line  115 . 
     As discussed above, a holding tank (not shown) may be included between the reaction zone  101  and distillation zone  102  for temporarily storing the liquid component from line  115 , for example from 1 to 24 hours, optionally at a temperature of about 21° C., and corresponding to an ethyl acetate formation of from 0.01 wt. % to 1.0 wt. % respectively. In addition, the rate at which the non-catalyzed reaction occurs may increase as the temperature of the crude alcohol product is increased. For example, as the temperature of the crude alcohol product in line  115  increases from 4° C. to 21° C., the rate of ethyl acetate formation may increase from about 0.01 wt. % per hour to about 0.005 wt. % per hour. Thus, in one embodiment, the temperature of liquid components in line  115  or in the optional holding tank is maintained at a temperature less than 21° C., e.g., less than 4° C. or less than −10° C. 
     In addition, it has now been discovered that the above-described equilibrium reaction may also favor ethanol formation in the top region of first column  107 . 
     The distillate, e.g., overhead stream, of first column  107  optionally is condensed and refluxed as shown in  FIGS. 1A-C , preferably, at a reflux ratio of 1:5 to 10:1. The distillate in line  117  preferably comprises ethanol and one or more higher alcohols, which may serve as an in situ denaturant, as well as ethyl acetate, acetaldehyde, water, and other impurities, which may be difficult to separate due to the formation of binary and tertiary azeotropes. The first distillate also comprises a significantly reduced amount of acetic acid and higher acid. As shown in  FIG. 1C , in some embodiments, the distillate of the first column (without further processing) is a denatured ethanol composition comprising from 0.0001 wt. % to 80 wt. % denaturant, e.g., from 0.001 wt. % to 60 wt. %, and from 20 wt. % to 75 wt. % ethanol, e.g., from 30 wt. % to 70 wt. %. Preferably, the denaturant in these embodiments is the higher alcohol optionally in combination with ethyl acetate and/or acetaldehyde. 
     In another embodiment, at least a portion of the first distillate may be combined, via optional line  117 ′, with a purified ethanol stream to form a denatured ethanol composition. Preferably, the denaturant comprises the higher alcohol optionally in combination with ethyl acetate and/or acetaldehyde. In another embodiment, at least a portion of the first distillate may be fed to an additional column, e.g., a third column as discussed below. As a result, the denaturant(s) in the first distillate, e.g., the higher alcohol, ethyl acetate and/or acetaldehyde, may be carried through to the distillate of the third column. As such, the third distillate may be denatured ethanol composition comprising the denaturant(s) from the first distillate. In these embodiments, the weight percentages of the denaturant(s) in the denatured ethanol composition may be as previously discussed. The weight ratio of the denaturant-containing stream, e.g., line  117 , and the purified ethanol stream vary widely and may be adjusted so as to achieve a particular desired concentration of denaturant in the denatured ethanol composition. For example, the weight ratio of the purified ethanol stream to the denaturant-containing stream may range from 0.01:1 to 5:1, e.g., from 0.05:1 to 3:1. 
     As discussed above, the residue from first column  107  comprises an amount of unreacted acetic acid and unreacted higher acid. Thus, in another embodiment, at least a portion of the first residue may be combined with a purified ethanol stream to form an acetic acid-denatured ethanol composition. 
     Beneficially, these denatured ethanol compositions are produced utilizing denaturant that is formed in situ via the hydrogenation reaction and without additional separation steps. As such, it is not necessary to provide an additional outside source of denaturant or to combine denaturant and purified ethanol, which eliminates a process step, and simplifies the overall process. It is also within the scope of the invention to further purify the first column distillate to remove, for example, additional water and/or acetaldehyde. Conventional separation methods may be used to achieve this additional purification. 
     As shown in Table 3, the first residue comprises a significant portion of unreacted acetic acid and heavier acid, which may, in turn, be recycled back to reactor  103 , as shown in  FIGS. 1A ,  1 B, and  1 C. 
     The first distillate in line  117  is introduced to the second column  108 , also referred to as the “light ends column,” preferably in the middle part of column  108 , e.g., middle half or middle third. Second column  108  may be a tray column or packed column. In one embodiment, second column  108  is a tray column having from 5 to 70 trays, e.g., from 15 to 50 trays or from 20 to 45 trays. 
     As one example, when a 25 tray column is utilized in a column without water extraction, line  117  is introduced at tray  17 . When the second column is not an extractive distillation column, it is expected that the ethyl acetate in line  117  may be separated into the second residue along with the ethanol, the higher alcohol and water. As a result, in one embodiment, more ethyl acetate may be fed to third column  109  and, thus, this ethyl acetate may be present in the third distillate. In other embodiments, at least a portion of the ethyl acetate-containing second residue may be combined with a purified ethanol stream to form a denatured ethanol composition comprising ethanol, the higher alcohol and ethyl acetate. 
     In preferred embodiments, however, the second column  108  may be an extractive distillation column. In extractive distillation columns, it is expected that the ethyl acetate in line  117  may be separated from the ethanol, the higher alcohol and water and pass into the second distillate. In such embodiments, an extraction agent, such as water, may be optionally added to second column  108  via line  127 . If the extraction agent comprises water, it may be obtained from an external source or from an internal return/recycle line from one or more of the other columns. In a preferred embodiment, the water in the third residue of third column  109  is utilized as the extraction agent. As shown in  FIGS. 1A ,  1 B, and  1 C, the third residue may be optionally directed to second column  108  via line  121 ′. 
     Although the temperature and pressure of second column  108  may vary, when at atmospheric pressure the temperature of the second residue exiting in line  118  from second column  108  preferably is from 60° C. to 90° C., e.g., from 70° C. to 90° C. or from 80° C. to 90° C. The temperature of the second distillate exiting in line  120  from second column  108  preferably is from 50° C. to 90° C., e.g., from 60° C. to 80° C. or from 60° C. to 70° C. Column  108  may operate at atmospheric pressure. In other embodiments, the pressure of second column  108  may range from 0.1 kPa to 510 kPa, e.g., from 1 kPa to 475 kPa or from 1 kPa to 375 kPa. Exemplary components for the distillate and residue compositions for second column  108  are provided in Table 4 below. It should be understood that the distillate and residue may also contain other components, not listed, such as components in the feed. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 SECOND COLUMN 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Distillate 
                   
                   
                   
               
               
                 Ethyl Acetate 
                 10 to 90 
                 25 to 90 
                 50 to 90 
               
               
                 Acetaldehyde 
                  1 to 25 
                  1 to 15 
                 1 to 8 
               
               
                 Water 
                  1 to 25 
                  1 to 20 
                  4 to 16 
               
               
                 Ethanol 
                 &lt;30 
                 0.001 to 15   
                 0.01 to 5   
               
               
                 Higher Alcohol* 
                 &lt;20 
                 &lt;10 
                 &lt;2 
               
               
                 Acetal 
                 &lt;5 
                 0.001 to 2    
                 0.01 to 1   
               
               
                 Residue 
               
               
                 Water 
                 30 to 70 
                 30 to 60 
                 30 to 50 
               
               
                 Ethanol 
                 20 to 75 
                 30 to 70 
                 40 to 70 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.04 to 20   
                 0.5 to 10  
               
               
                 Ethyl Acetate 
                 &lt;3 
                 0.001 to 2    
                 0.001 to 0.5  
               
               
                 Acetic Acid 
                 &lt;0.5 
                 0.001 to 0.3  
                 0.001 to 0.2  
               
               
                 Higher Acid** 
                 &lt;0.5 
                 0.001 to 0.3  
                 0.001 to 0.2  
               
               
                   
               
            
           
         
       
     
     The weight ratio of alcohols (ethanol and higher alcohols) in the second residue to alcohols in the second distillate preferably is at least 3:1, e.g., at least 6:1, at least 8:1, at least 10:1 or at least 15:1. The weight ratio of ethyl acetate in the second residue to ethyl acetate in the second distillate preferably is less than 0.4:1, e.g., less than 0.2:1 or less than 0.1:1. In embodiments that use an extractive column with water as an extraction agent as the second column  108 , the weight ratio of ethyl acetate in the second residue to ethyl acetate in the second distillate approaches zero. Thus, as shown in Table 4, the second distillate in line  120 , which is a derivative stream of the crude alcohol product, comprises a significant amount of separated, in situ, denaturant and the second residue in line  118  comprises a significant amount of alcohols (ethanol and higher alcohols). In some embodiments, the second distillate comprises diethyl ether. The diethyl ether may be present in amounts ranging from 0.1 wt. % to 20 wt. %, e.g., 0.1 wt. % to 10 wt. %, from 1 wt. % to 9 wt. %, or from 3 wt. % to 7 wt. %. In these cases, the second distillate may be a denatured ethanol composition having a denaturant comprising the higher alcohol and diethyl ether. In one embodiment, the second residue in line  118  further comprises isopropanol. The isopropanol may be derived from acetone via the methods discussed above. The acetone, for example, may be formed in situ in the hydrogenation and/or the acetone may be added to the hydrogenation reactor as a reactant. Thus, in embodiments where a sufficient amount of isopropanol, e.g., from 0.1 wt. % to 10 wt. %, from 1 wt. % to 9 wt. %, or from 3 wt. % to 7 wt. %, is present in the second residue, the second residue may be a denatured ethanol composition having an isopropanol denaturant. 
     In another embodiment of the invention as shown in  FIG. 1A , at least a portion of the second distillate is directed, e.g., via line  120 , to the purified mixed alcohol composition exiting third column  109 . In this case, the denatured ethanol composition results from the addition of the in situ-formed non-alcohol denaturant to the purified mixed alcohol composition. Preferably, ethyl acetate denaturant in the second distillate is combined with the purified mixed alcohol composition obtained from third column  109 . In other embodiments, acetaldehyde denaturant in the second distillate is combined with the purified mixed alcohol composition obtained from third column  109 . In other embodiments, at least a portion of the second distillate is fed to third column  109 . In these cases, at least a portion of the denaturant in the second distillate, e.g., ethyl acetate and/or acetaldehyde, follows the ethanol through third column  109  along with the higher alcohol. Other impurities in the second distillate may be withdrawn in the residue of the third column  109 . As a result, the third distillate comprises ethanol and the higher alcohol along with denaturant from the second column distillate. Denatured ethanol compositions thus formed may have the characteristics and composition of the denatured ethanol compositions discussed herein. The weight ratio of the denaturant-containing stream, e.g., line  120 , and the purified mixed alcohol stream vary widely and may be adjusted so as to achieve a particular desired concentration of ethanol and higher alcohol as well as additional denaturant. For example, when ethyl acetate is the additional denaturant, the weight ratio of the purified mixed alcohol stream to the denaturant-containing stream may range from 100:1 to 1:1, e.g., from 25:1 to 5:1. 
     In another embodiment, at least a portion of the second distillate is recycled to reactor  103  (not shown). As shown, the second residue from the bottom of second column  108 , which comprises ethanol, higher alcohol and water, is fed via line  118  to third column  109 , also referred to as the “product column.” More preferably, the second residue in line  118  is introduced in the lower part of third column  109 , e.g., lower half or lower third. Third column  109  recovers ethanol and the higher alcohols, which preferably is substantially pure mixed alcohol composition other than the azeotropic water content, as the distillate in line  119 . Particularly heavy alcohols may be separated into the third residue  121 . The distillate of third column  109  preferably is refluxed as shown in  FIG. 1A , for example, at a reflux ratio of from 1:10 to 10:1, e.g., from 1:3 to 3:1 or from 1:2 to 2:1. The third residue in line  121 , which preferably comprises primarily water, preferably is removed from the system  100  or may be partially returned to any portion of the system  100 . Third column  109  is preferably a tray column as described above and preferably operates at atmospheric pressure. The temperature of the third distillate exiting in line  119  from third column  109  preferably is from 60° C. to 110° C., e.g., from 70° C. to 100° C. or from 75° C. to 95° C. The temperature of the third residue exiting from third column  109  preferably is from 70° C. to 115° C., e.g., from 80° C. to 110° C. or from 85° C. to 105° C., when the column is operated at atmospheric pressure. Exemplary components of the distillate, residue, and optional side stream compositions for third column  109  are provided in Table 5 below. As shown in Table 5, the third distillate may comprise significant amounts of higher alcohol denaturant, preferably propanol denaturant. In these cases, the third distillate may be a denatured ethanol composition. It should be understood that the distillate and residue may also contain other components, not listed, such as components from the feed. 
     As separation occurs in the third column, the composition of the stream being separated may vary from tray to tray in the third column. In some embodiments, the composition of the stream within the third column, depending upon operating conditions, may contain an increased concentration or build up of higher alcohols, e.g., mid-boiling alcohols having a boiling point lower than that of water and higher than that of an ethanol/water low-boiling azeotrope. Examples of these higher alcohols include n-propanol (boiling point 97.1° C.), isopropanol (boiling point 82.5° C.), and 2-butanol (boiling point 99.5° C.). Some of these alcohols are formed in situ as a result of the acetic acid hydrogenation and/or from the hydrogenation of the higher acids. These in situ-formed higher alcohols may be utilized as denaturants. 
     The mid-boiling point higher alcohols may be removed using one or more side streams  138  drawn from third column  109 . Preferably, side stream  138  is drawn from a middle or an upper section of third column  109 , above the feed point of the second residue. Most preferably, side stream  138  is drawn from above the tray  25 , e.g., from above tray  30 , or from above tray  40 . By adjusting the process parameters of third column  109  and withdrawing side stream  138  at the appropriate location, side stream  138  may be used to remove a significant portion of mid-boiling point alcohols, e.g., n-propanol, as desired, from the feed in line  118 . Side stream  138  may comprise, for example, from 0.01 wt. % to 10 wt. % n-propanol, e.g., from 0.01 to 5 wt. % or from 0.01 wt. % to 3 wt. %. By withdrawing side stream  138 , a significant amount of propanol, e.g., n-propanol, may be removed resulting in the purification of the ethanol in the third distillate in line  119 , if desired. It is within the scope of the invention to select, based on column configuration and operating conditions, an appropriate tray in a column from which to draw a particular side stream. Also, the contents of side stream  138  may constitute a denatured ethanol composition comprising ethanol and mid-boiling heavier alcohols such as propanol, e.g., n-propanol. Thus, in this embodiment, a pure ethanol composition may be co-produced with a denatured ethanol composition. In other embodiments, side stream  138  and the third distillate are each, independently of one another, denatured ethanol compositions. For example, side stream  130  may comprise a heavier alcohol-denatured ethanol composition, e.g., an n-propanol-denatured ethanol composition, and third distillate  119  may comprise an ethyl acetate-denatured ethanol composition. By performing the separation in this manner, the resultant third distillate  119  comprises less heavier alcohol than the side stream, which may be desired for certain ethanol applications. In other embodiments, at least a portion of withdrawn side stream  138  may be combined with third distillate  119  to form a denatured ethanol composition comprising at least a portion of the in situ-formed denaturant from side stream  130 . 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 THIRD COLUMN 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Distillate 
                   
                   
                   
               
               
                 Ethanol 
                 75 to 96 
                  80 to 96 
                 85 to 96 
               
               
                 Heavier Alcohol* 
                 0.01 to 20   
                  0.04 to 20 
                 0.5 to 10  
               
               
                 Water 
                 &lt;12 
                  1 to 9 
                 3 to 8 
               
               
                 Acetic Acid 
                 &lt;1 
                 0.001 to 0.1 
                 0.005 to 0.01  
               
               
                 Ethyl Acetate 
                 &lt;5 
                 0.001 to 4   
                 0.01 to 3   
               
               
                 Isopropanol 
                 0.07 to 10   
                  0.8 to 7 
                 2.5 to 7   
               
               
                 Residue 
               
               
                 Water 
                  75 to 100 
                   80 to 100 
                  90 to 100 
               
               
                 Ethanol 
                 &lt;0.8 
                 0.001 to 0.5 
                 0.005 to 0.05  
               
               
                 Heavier Alcohol* 
                 &lt;0.8 
                 0.001 to 0.5 
                 0.005 to 0.05  
               
               
                 Ethyl Acetate 
                 &lt;1 
                 0.001 to 0.5 
                 0.005 to 0.2  
               
               
                 Acetic Acid 
                 &lt;2 
                 0.001 to 0.5 
                 0.005 to 0.2  
               
               
                 Side Stream (Optional) 
               
               
                 Ethanol 
                 0.01 to 10   
                 0.01 to 5  
                 0.01 to 3   
               
               
                 n-propanol 
                 0.1 to 10  
                 0.25 to 8  
                 1.5 to 6.3 
               
               
                   
               
            
           
         
       
     
     Concentrations of the heavier alcohols will vary widely depending on the boiling point of the various heavier alcohols as well as whether a side stream is employed. 
     Any of the compounds that are carried through the distillation process from the feed or crude reaction product generally remain in the third distillate in amounts of less 0.1 wt. %, based on the total weight of the third distillate composition, e.g., less than 0.05 wt. % or less than 0.02 wt. %. In one embodiment, one or more side streams may remove impurities from any of the columns  107 ,  108 , and/or  109  in system  100 . In one embodiment, at least one side stream may be used to remove impurities from the third column  109 . The impurities may be purged and/or retained within the system  100 . 
     The third distillate in line  119  may be further purified to form an anhydrous mixed alcohol product stream, i.e., “finished anhydrous alcohol,” using one or more additional separation systems, such as, for example, distillation columns (e.g., a finishing column) or molecular sieves. 
     Returning to second column  108 , the distillate in line  120  preferably is refluxed as shown in  FIGS. 1A ,  1 B, and  1 C, for example, at a reflux ratio of from 1:10 to 10:1, e.g., from 1:5 to 5:1 or from 1:3 to 3:1. As noted above, the second distillate may comprise a significant portion denaturants, e.g., ethyl acetate and/or acetaldehyde. Accordingly, all or a portion of the second distillate, as shown by line  120 , may be directed downstream and may be combined with the mixed alcohols that have been further purified, e.g., via third column  109 . Also, at least a portion of the distillate from second column  108  may be purged if necessary. In another embodiment, as shown in  FIG. 1B , a portion of the second distillate from second column  108  may be recycled to reaction zone  101  via line  120  in order to convert ethyl acetate to additional ethanol, e.g., may be recycled to reactor  103  and co-fed along with acid feed line  105 . In another embodiment, the second distillate in line  120  may be further purified to remove other components, such as acetaldehyde, using one or more additional columns (not shown). Such a configuration may be utilized in a case where the desired denaturant consists essentially of ethyl acetate, e.g., Formulae 35 or 35-A of Title 27, Part 21 of the US Code of Federal Regulations (hereinafter abbreviated as 27 C.F.R. Part 21), the entirety of which is incorporated herein by reference. As another option, additional columns (not shown) may be utilized to remove the ethyl acetate and leave acetaldehyde, which may be useful in a situation where the desired denaturant comprises acetaldehyde and does not comprise ethyl acetate. 
     System  100  in  FIG. 1C  is similar to that of  FIGS. 1A and 1B , with the addition that the second distillate in line  120  is fed to fourth column  123 , also referred to as the “acetaldehyde removal column.” In fourth column  123 , the second distillate is separated into a fourth distillate, which comprises acetaldehyde in line  124  and a fourth residue, which comprises ethyl acetate in line  125 . The fourth distillate preferably is refluxed at a reflux ratio of from 1:20 to 20:1, e.g., from 1:10 to 10:1 or from 1:5 to 5:1, and at least a portion of the fourth distillate may be returned to the reaction zone  101  as shown by line  124 . For example, the fourth distillate may be combined with the acid feed, added to the vaporizer  110 , or added directly to the reactor  103 . As shown, the fourth distillate is co-fed with the acetic acid in feed line  105  to vaporizer  110 . Without being bound by theory, since acetaldehyde may be hydrogenated to form ethanol, the recycling of a stream that contains acetaldehyde to the reaction zone increases the yield of ethanol and decreases byproduct and waste generation. In another embodiment (not shown in the figure), the acetaldehyde may be collected and utilized, with or without further purification, to make useful products including but not limited to n-butanol, 1,3-butanediol, and/or crotonaldehyde and derivatives. In one preferred embodiment, the acetaldehyde is removed from the second distillate in fourth column  123  such that no detectable amount of acetaldehyde is present in the residue of column  123 . 
     In preferred embodiments, at least a portion of fourth distillate is combined (not shown) with the purified mixed alcohol stream comprising the ethanol and heavier alcohol to form a denatured ethanol composition. Preferably, the denaturant comprises the heavier alcohol as well as acetaldehyde and/or ethyl acetate. In other embodiments, at least a portion of the fourth distillate may be fed to third column  109 . As a result, in these embodiments, the distillate exiting third column  109  may comprise at least a portion of the in situ-formed acetaldehyde and/or ethyl acetate that was present in the fourth distillate. In these embodiments, the weight percentages of the acetaldehyde denaturant in the denatured ethanol composition may be as previously discussed. The weight ratio of the purified mixed alcohol stream and the fourth distillate may vary widely and may be adjusted so as to achieve a particular desired concentration of non-alcohol denaturant in the denatured ethanol composition. For example, the weight ratio of the purified mixed alcohol stream to the fourth distillate may range from 2:1 to 75:1, e.g., from 7:1 to 50:1. 
     The fourth residue primarily comprises ethyl acetate and ethanol. Preferably, at least a portion of fourth residue is combined with the purified mixed alcohol stream to form a denatured ethanol composition. Preferably, the denaturant comprises ethyl acetate as well as the heavier alcohol. In other embodiments, at least a portion of the fourth residue may be fed to third column  109 . As a result, in these embodiments, the distillate exiting third column  109  may comprise at least a portion of the in situ-formed ethyl acetate that was present in the fourth residue. In these embodiments, the weight percentages of the ethyl acetate denaturant in the denatured ethanol composition may be as previously discussed. The weight ratio of the purified mixed alcohol stream and the fourth residue may vary widely and may be adjusted so as to achieve a particular desired concentration of denaturant in the denatured ethanol composition. For example, the weight ratio of the purified mixed alcohol stream to the fourth residue may range from 1:1 to 50:1, e.g., from 1.75:1 to 20:1. The fourth residue of fourth column  123 , in other embodiments, may be purged via line  125 . 
     Fourth column  123  is preferably a tray column as described above and preferably operates above atmospheric pressure. In one embodiment, the pressure is from 120 KPa to 5,000 KPa, e.g., from 200 KPa to 4,500 KPa, or from 400 KPa to 3,000 KPa. In a preferred embodiment the fourth column  123  may operate at a pressure that is higher than the pressure of the other columns. 
     The temperature of the fourth distillate exiting in line  124  from fourth column  123  preferably is from 60° C. to 110° C., e.g., from 70° C. to 100° C. or from 75° C. to 95° C. The temperature of the residue exiting from fourth column  125  preferably is from 70° C. to 115° C., e.g., from 80° C. to 110° C. or from 85° C. to 110° C. Exemplary components of the distillate and residue compositions for fourth column  123  are provided in Table 6 below. It should be understood that the distillate and residue may also contain other components, not listed, such as components in the feed. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 FOURTH COLUMN 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Distillate 
                   
                   
                   
               
               
                 Acetaldehyde 
                 2 to 80 
                    2 to 50 
                   5 to 40 
               
               
                 Ethyl Acetate 
                 &lt;90 
                   30 to 80 
                   40 to 75 
               
               
                 Ethanol 
                 &lt;30 
                 0.001 to 25 
                 0.01 to 20 
               
               
                 Heavier Alcohol* 
                 &lt;30 
                 0.001 to 25 
                 0.01 to 20 
               
               
                 Water 
                 &lt;25 
                 0.001 to 20 
                 0.01 to 15 
               
               
                 Residue 
               
               
                 Ethyl Acetate 
                 40 to 100 
                    50 to 100 
                   60 to 100 
               
               
                 Ethanol 
                 &lt;40 
                 0.001 to 30 
                 0.01 to 15 
               
               
                 Heavier Alcohol* 
                 &lt;40 
                 0.001 to 30 
                 0.01 to 15 
               
               
                 Water 
                 &lt;25 
                 0.001 to 20 
                   2 to 15 
               
               
                 Acetaldehyde 
                  &lt;1 
                  0.001 to 0.5 
                 Not detectable 
               
               
                 Acetal 
                  &lt;3 
                 0.001 to 2  
                 0.01 to 1  
               
               
                   
               
            
           
         
       
     
       FIG. 1C  also shows that the third residue in line  121  may be recycled to second column  108 . In one embodiment, recycling the third residue further reduces the aldehyde components in the second residue and concentrates these aldehyde components in the distillate stream  120  and thereby sent to the fourth column  123 , wherein the aldehydes may be more easily separated in the fourth column  123 . Such embodiments also provide a finished ethanol product that preferably has low amounts of aldehydes and esters. 
     In several embodiments, denaturant-containing streams are combined with purified mixed alcohol streams to form denatured ethanol compositions. In other embodiments, these denaturant-containing streams may be fed to third column  109 , as opposed to being combined with the distillate of third column  109 . In these cases, the denaturants that are fed to column  109  may be separated in the distillate of the third column  109  and, as such may be present in the purified mixed alcohol stream. Thus, the third distillate may comprise a denatured ethanol composition. 
     Alternative two-column separation schemes are illustrated in  FIGS. 2 and 3 . In  FIG. 2 , crude alcohol product in line  115  is introduced in the middle or lower portion of a first column  150 , also referred to as acid-water column. For purposes of convenience, the columns in each exemplary separation process, may be referred as the first, second, third, etc., columns, but it is understood that first column  150  in  FIG. 2  operates differently than the first column  107  of  FIGS. 1A-1C . In one embodiment, no entrainers are added to first column  150 . In  FIG. 2 , first column  150 , water and unreacted acetic acid and unreacted heavier acid, along with any other heavy components, if present, are removed from stream  115  and are withdrawn, preferably continuously, as a first residue in line  151 . Preferably, a substantial portion of the water in the crude alcohol product that is fed to first column  150  may be removed in the first residue, for example, up to about 90% of the water from the crude ethanol product, and more preferably up to about 75%. First column  150  also forms a first distillate, which is withdrawn in line  152 . 
     When column  150  is operated under about 170 kPa, the temperature of the residue exiting in line  151  preferably is from 90° C. to 130° C., e.g., from 95° C. to 120° C. or from 100° C. to 115° C. The temperature of the distillate exiting in line  152  preferably is from 60° C. to 90° C., e.g., from 65° C. to 85° C. or from 70° C. to 80° C. In some embodiments, the pressure of first column  150  may range from 0.1 kPa to 510 kPa, e.g., from 1 kPa to 475 kPa or from 1 kPa to 375 kPa. 
     The first distillate in line  152  comprises water, in addition to ethanol, the higher alcohol and other organics. In terms of ranges, the concentration of water in the first distillate in line  152  preferably is from 4 wt. % to 38 wt. %, e.g., from 7 wt. % to 32 wt. %, or from 7 to 25 wt. %. A portion of first distillate in line  153  may be condensed and refluxed, for example, at a ratio of from 10:1 to 1:10, e.g., from 3:1 to 1:3 or from 1:2 to 2:1. It is understood that reflux ratios may vary with the number of stages, feed locations, column efficiency and/or feed composition. Operating with a reflux ratio of greater than 3:1 may be less preferred because more energy may be required to operate the first column  150 . The condensed portion of the first distillate may also be fed to a second column  154 . 
     The remaining portion of the first distillate in  155  is fed to a water separation unit  156 . Water separation unit  156  may be an adsorption unit, membrane, molecular sieves, extractive column distillation, or a combination thereof. A membrane or an array of membranes may also be employed to separate water from the distillate. The membrane or array of membranes may be selected from any suitable membrane that is capable of removing a permeate water stream from a stream that also comprises ethanol and ethyl acetate. 
     In a preferred embodiment, water separation unit  156  is a pressure swing adsorption (PSA) unit. The PSA unit is optionally operated at a temperature from 30° C. to 160° C., e.g., from 80° C. to 140° C., and a pressure of from 0.01 kPa to 550 kPa, e.g., from 1 kPa to 150 kPa. The PSA unit may comprise two to five beds. Water separation unit  156  may remove at least 95% of the water from the portion of first distillate in line  155 , and more preferably from 99% to 99.99% of the water from the first distillate, in a water stream  157 . All or a portion of water stream  157  may be returned to column  150  in line  158 , where the water preferably is ultimately recovered from column  150  in the first residue in line  151 . Additionally or alternatively, all or a portion of water stream  157  may be purged via line  159 . The remaining portion of first distillate exits the water separation unit  156  as mixed alcohol stream  160 . Mixed alcohol stream  160  may have a low concentration of water of less than 10 wt. %, e.g., less than 6 wt. % or less than 2 wt. %. Exemplary components of mixed alcohol stream  160  and first residue in line  151  are provided in Table 7 below. It should also be understood that these streams may also contain other components, not listed, such as components derived from the feed. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 FIRST COLUMN 150 WITH PSA (FIG. 2) 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Mixed Alcohol Stream 
                   
                   
                   
               
               
                 Ethanol 
                 20 to 95 
                 30 to 95 
                 40 to 95 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.04 to 20   
                 2 to 8 
               
               
                 Water 
                 &lt;10 
                 0.01 to 6   
                 0.1 to 2   
               
               
                 Acetic Acid 
                 &lt;2 
                 0.001 to 0.5  
                 0.01 to 0.2  
               
               
                 Higher Acid** 
                 &lt;2 
                 0.001 to 0.5  
                 0.01 to 0.2  
               
               
                 Ethyl Acetate 
                 &lt;60 
                  1 to 55 
                  5 to 55 
               
               
                 Acetaldehyde 
                 &lt;1 
                 0.001 to 0.5  
                 0.005 to 0.05  
               
               
                 Acetal 
                 &lt;0.1 
                 &lt;0.05 
                 &lt;0.01 
               
               
                 Acetone 
                 &lt;0.05 
                 0.001 to 0.03  
                  0.01 to 0.025 
               
               
                 Residue 
               
               
                 Acetic Acid 
                 &lt;90 
                  1 to 50 
                  2 to 35 
               
               
                 Higher Acid** 
                 0.1 to 40  
                  1 to 20 
                  1 to 10 
               
               
                 Water 
                  30 to 100 
                 45 to 95 
                 60 to 90 
               
               
                 Ethanol 
                 &lt;1 
                 &lt;0.9 
                 &lt;0.3 
               
               
                 Higher Alcohol* 
                 &lt;1 
                 &lt;0.9 
                 &lt;0.3 
               
               
                   
               
            
           
         
       
     
     Preferably, mixed alcohol stream  160  is not returned or refluxed to first column  150 . The condensed portion of the first distillate in line  153  may be combined with mixed alcohol stream  160  to control the amount of water fed to the second column  154 . For example, in some embodiments the first distillate may be split into equal portions, while in other embodiments, all of the first distillate may be condensed or all of the first distillate may be processed in the water separation unit. In  FIG. 2 , the condensed portion in line  153  and mixed alcohol stream  160  are co-fed to second column  154 . In other embodiments, the condensed portion in line  153  and mixed alcohol stream  160  may be separately fed to second column  154 . The combined distillate and mixed alcohol stream preferably has a total water concentration of greater than 0.5 wt. %, e.g., greater than 2 wt. % or greater than 5 wt. %. In terms of ranges, the total water concentration of the combined distillate and mixed alcohol stream may be from 0.5 to 15 wt. %, e.g., from 2 to 12 wt. %, or from 5 to 10 wt. %. 
     The second column  154  in  FIG. 2 , also referred to as the “light ends column,” removes ethyl acetate and acetaldehyde from the first distillate in line  153  and/or mixed alcohol stream  160 . Ethyl acetate and acetaldehyde are removed as a second distillate in line  161  and ethanol and the higher alcohol are removed as the second residue in line  162 . Second column  154  may be a tray column or packed column. In one embodiment, second column  154  is a tray column having from 5 to 70 trays, e.g., from 15 to 50 trays or from 20 to 45 trays. 
     Second column  154  operates at a pressure ranging from 0.1 kPa to 510 kPa, e.g., from 10 kPa to 450 kPa or from 50 kPa to 350 kPa. Although the temperature of second column  154  may vary, when at about 20 kPa to 70 kPa, the temperature of the second residue exiting in line  162  preferably is from 30° C. to 75° C., e.g., from 35° C. to 70° C. or from 40° C. to 65° C. The temperature of the second distillate exiting in line  161  preferably is from 20° C. to 55° C., e.g., from 25° C. to 50° C. or from 30° C. to 45° C. 
     The total concentration of water fed to second column  154  preferably is less than 10 wt. %, as discussed above. When first distillate in line  153  and/or mixed alcohol stream  160  comprises minor amounts of water, e.g., less than 1 wt. % or less than 0.5 wt. %, additional water may be fed to the second column  154  as an extractive agent in the upper portion of the column. A sufficient amount of water is preferably added via the extractive agent such that the total concentration of water fed to second column  154  is from 1 to 10 wt. % water, e.g., from 2 to 6 wt. %, based on the total weight of all components fed to second column  154 . If the extractive agent comprises water, the water may be obtained from an external source or from an internal return/recycle line from one or more of the other columns or water separators. 
     Suitable extractive agents may also include, for example, dimethylsulfoxide, glycerine, diethylene glycol, 1-naphthol, hydroquinone, N,N′-dimethylformamide, 1,4-butanediol; ethylene glycol-1,5-pentanediol; propylene glycol-tetraethylene glycol-polyethylene glycol; glycerine-propylene glycol-tetraethylene glycol-1,4-butanediol, ethyl ether, methyl formate, cyclohexane, N,N-dimethyl-1,3-propanediamine, N,N′-dimethylethylenediamine, diethylene triamine, hexamethylene diamine and 1,3-diaminopentane, an alkylated thiopene, dodecane, tridecane, tetradecane, chlorinated paraffins, or a combination thereof. When extractive agents are used, a suitable recovery system, such as a further distillation column, may be used to recycle the extractive agent. 
     Exemplary components for the second distillate and second residue compositions for the second column  154  are provided in Table 8, below. It should be understood that the distillate and residue may also contain other components, not listed in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 SECOND COLUMN 154 (FIG. 2) 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Second Distillate 
                   
                   
                   
               
               
                 Ethyl Acetate 
                 5 to 90 
                   10 to 80 
                 15 to 75 
               
               
                 Acetaldehyde 
                 &lt;10 
                 0.005 to 2  
                 0.01 to 1   
               
               
                 Ethanol 
                 &lt;45 
                 0.001 to 40 
                 0.01 to 35   
               
               
                 Higher Alcohol* 
                 &lt;45 
                 0.001 to 40 
                 0.01 to 35   
               
               
                 Water 
                 &lt;20 
                  0.01 to 10 
                 0.1 to 5   
               
               
                 Second Residue 
               
               
                 Ethanol 
                  80 to 99.5 
                     85 to 99.5 
                   90 to 99.5 
               
               
                 Heavier Alcohol* 
                 0.01 to 20   
                  0.04 to 20 
                 0.5 to 10  
               
               
                 Water 
                 &lt;20 
                 0.001 to 15 
                 0.01 to 10   
               
               
                 Ethyl Acetate 
                 &lt;1 
                 0.001 to 2  
                 0.001 to 0.5  
               
               
                 Acetic Acid 
                 &lt;0.5 
                 &lt;0.01 
                 0.001 to 0.01  
               
               
                 Heavier Acid** 
                 &lt;0.5 
                 &lt;0.01 
                 0.001 to 0.01  
               
               
                   
               
            
           
         
       
     
     The second distillate in line  161 , which comprises ethyl acetate and/or acetaldehyde, preferably is refluxed as shown in  FIG. 2 , for example, at a reflux ratio of from 1:30 to 30:1, e.g., from 1:10 to 10:1 or from 1:3 to 3:1. In one aspect, not shown, the second distillate  161  or a portion thereof may be returned to the reaction zone (shown in  FIGS. 1A-1C ). The ethyl acetate and/or acetaldehyde in the second distillate may be further reacted in reaction zone. 
     In one embodiment, the second distillate in line  161  and/or a refined second distillate, or a portion of either or both streams, may be further separated to produce an acetaldehyde-containing stream and an ethyl acetate-containing stream similar to the optional fourth column in  FIG. 1C . This may allow a portion of either the resulting acetaldehyde-containing stream or ethyl acetate-containing stream to be recycled to the reactor while purging the other stream. The purge stream may be valuable as a source of either ethyl acetate and/or acetaldehyde. 
       FIG. 3  is another exemplary separation system to recover a mixed alcohol stream comprising ethanol and the heavier alcohol from the second reaction mixture. Stream  115  is introduced in the upper part of first column  170 , e.g., upper half or upper third. In one embodiment, no entrainers are added to first column  170 . In first column  170 , a weight majority of the ethanol, higher alcohol, water, acetic acid, higher acid, and other heavy components, if present, are removed from stream  115  and are withdrawn, preferably continuously, as residue in line  171 . First column  170  also forms an overhead distillate, which is withdrawn in line  172 , and which may be condensed and refluxed, for example, at a ratio of from 30:1 to 1:30, e.g., from 10:1 to 1:10 or from 1:5 to 5:1. The overhead distillate in stream  172  preferably comprises a weight majority of the ethyl acetate from stream  115 . 
     When column  170  is operated under about 170 kPa, the temperature of the residue exiting in line  171  preferably is from 70° C. to 155° C., e.g., from 90° C. to 130° C. or from 100° C. to 110° C. The base of column  170  may be maintained at a relatively low temperature by withdrawing a residue stream comprising ethanol, higher alcohol(s), water, acetic acid, and higher acid(s), thereby providing an energy efficiency advantage. The temperature of the distillate exiting in line  172  preferably at 170 kPa is from 75° C. to 100° C., e.g., from 75° C. to 83° C. or from 81° C. to 84° C. In some embodiments, the pressure of first column  170  may range from 0.1 kPa to 510 kPa, e.g., from 1 kPa to 475 kPa or from 1 kPa to 375 kPa. Exemplary components of the distillate and residue compositions for first column  170  are provided in Table 9 below. It should also be understood that the distillate and residue may also contain other components, not listed in Table 9. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 FIRST COLUMN 170 (FIG. 3) 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %)  
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Distillate 
                   
                   
                   
               
               
                 Ethyl Acetate 
                 10 to 85 
                 15 to 80 
                 20 to 75 
               
               
                 Acetaldehyde 
                 &lt;0.1 
                 0.0001 to 0.05  
                 0.005 to 0.025 
               
               
                 Acetal 
                 &lt;0.1 
                 0.0001 to 0.05  
                 0.005 to 0.025 
               
               
                 Acetone 
                 &lt;0.05 
                 0.001 to 0.03  
                  0.01 to 0.025 
               
               
                 Ethanol 
                  3 to 55 
                  4 to 50 
                  5 to 45 
               
               
                 Higher Alcohol* 
                  3 to 55 
                  4 to 50 
                  5 to 45 
               
               
                 Water 
                 0.1 to 20  
                  1 to 15 
                  2 to 10 
               
               
                 Acetic Acid 
                 &lt;2 
                 &lt;0.1 
                 &lt;0.05 
               
               
                 Higher Acid** 
                 &lt;2 
                 &lt;0.1 
                 &lt;0.05 
               
               
                 Residue 
               
               
                 Acetic Acid 
                 0.01 to 35   
                 0.1 to 30  
                 0.2 to 25  
               
               
                 Higher Acid** 
                 0.01 to 35   
                 0.1 to 30  
                 0.2 to 25  
               
               
                 Water 
                 25 to 70 
                 30 to 65 
                 35 to 60 
               
               
                 Ethanol 
                 10 to 75 
                 15 to 70 
                 20 to 65 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.04 to 20   
                 0.5 to 10  
               
               
                   
               
            
           
         
       
     
     In an embodiment of the present invention, column  170  may be operated at a temperature where most of the water, ethanol, higher alcohol, acetic acid, and higher acid are removed from the residue stream and only a small amount of ethanol, higher alcohol, and water is collected in the distillate stream due to the formation of binary and tertiary azeotropes. The weight ratio of water in the residue in line  171  to water in the distillate in line  172  may be greater than 1:1, e.g., greater than 2:1. The weight ratio of alcohols in the residue to alcohols in the distillate may be greater than 1:1, e.g., greater than 2:1 
     The amount of acids in the first residue may vary depending primarily on the conversion in the reaction zone. In one embodiment, when the conversion is high, e.g., greater than 90%, the amount of acid (collectively) in the first residue may be less than 10 wt. %, e.g., less than 5 wt. % or less than 2 wt. %. In other embodiments, when the conversion is lower, e.g., less than 90%, the amount of acid in the first residue may be greater than 10 wt. %. 
     The distillate preferably is substantially free of acid, e.g., comprising less than 1000 ppm, less than 500 ppm or less than 100 ppm acetic acid and higher acid. The distillate may be purged from the system or recycled in whole or part to reaction zone. In some embodiments, the distillate may be further separated, e.g., in a distillation column (not shown), into an acetaldehyde stream and an ethyl acetate stream. Either of these streams may be returned to the reaction zone or separated from the system as a separate product. 
     Some species, such as acetals, may decompose in first column  170  such that very low amounts, or even no detectable amounts, of acetals remain in the distillate or residue. 
     To recover the ethanol and higher alcohols, the residue in line  171  may be further separated in a second column  173 , also referred to as an “acid separation column.” An acid separation column may be used when the acid concentration (acetic acid and higher acid concentration) in the first residue is greater than 1 wt. %, e.g., greater than 5 wt. %. The first residue in line  171  is introduced to second column  173  preferably in the top part of column  173 , e.g., top half or top third. Second column  173  yields a second residue in line  174  comprising acetic acid, higher acid and water, and a second distillate in line  175  comprising ethanol and the higher alcohol. Second column  173  may be a tray column or packed column. In one embodiment, second column  173  is a tray column having from 5 to 150 trays, e.g., from 15 to 50 trays or from 20 to 45 trays. Although the temperature and pressure of second column  173  may vary, when at atmospheric pressure the temperature of the second residue exiting in line  174  preferably is from 95° C. to 130° C., e.g., from 100° C. to 125° C. or from 110° C. to 120° C. The temperature of the second distillate exiting in line  175  preferably is from 60° C. to 105° C., e.g., from 75° C. to 100° C. or from 80° C. to 100° C. The pressure of second column  173  may range from 0.1 kPa to 510 kPa, e.g., from 1 kPa to 475 kPa or from 1 kPa to 375 kPa. Exemplary components for the distillate and residue compositions for second column  173  are provided in Table 10 below. It should be understood that the distillate and residue may also contain other components, not listed in Table 10. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 SECOND COLUMN 173 (FIG. 3) 
               
            
           
           
               
               
               
               
            
               
                   
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Second Distillate 
                   
                   
                   
               
               
                 Ethanol 
                   70 to 99.9 
                   75 to 99.5 
                   80 to 99.5 
               
               
                 Higher Alcohol* 
                 0.01 to 20   
                 0.01 to 20   
                 0.5 to 10  
               
               
                 Ethyl Acetate 
                 &lt;10  
                 0.001 to 5    
                 0.01 to 3   
               
               
                 Acetaldehyde 
                 &lt;5 
                 0.001 to 1    
                 0.005 to 0.5  
               
               
                 Water 
                 0.1 to 30  
                 0.5 to 25  
                 0.5 to 20  
               
               
                 Second Residue 
               
               
                 Acetic Acid 
                 0.1 to 45  
                 0.2 to 40  
                 0.5 to 35  
               
               
                 Higher Acid** 
                 0.01 to 30   
                 0.2 to 20  
                 0.5 to 10  
               
               
                 Water 
                  45 to 100 
                   55 to 99.8 
                   65 to 99.5 
               
               
                 Ethyl Acetate 
                 &lt;2 
                 &lt;1 
                 &lt;0.5 
               
               
                 Ethanol 
                 &lt;5 
                 0.001 to 5    
                 &lt;2 
               
               
                 Higher Alchol* 
                 &lt;5 
                 0.001 to 5    
                 &lt;2 
               
               
                   
               
            
           
         
       
     
     The weight ratio of alcohols in the second distillate in line  175  to alcohols in the second residue in line  174  preferably is at least 35:1. In one embodiment, the weight ratio of water in the second residue  174  to water in the second distillate  175  is greater than 2:1, e.g., greater than 4:1 or greater than 6:1. In addition, the weight ratio of acids in the second residue  174  to acids in the second distillate  175  preferably is greater than 10:1, e.g., greater than 15:1 or greater than 20:1. Preferably, the second distillate in line  175  is substantially free of acetic acid and higher acid and may only contain, if any, trace amounts of acid. Preferably, the second distillate in line  175  contains substantially no ethyl acetate. 
     The remaining water from the second distillate in line  175  may be removed in further embodiments of the present invention. Depending on the water concentration, the alcohol product, comprising ethanol and higher alcohol, may be derived from the second distillate in line  175 . Some ethanol applications, such as industrial ethanol applications, may tolerate water in the product, while other applications, such as fuel applications, may require an anhydrous composition. The amount of water in the distillate of line  175  may be closer to the azeotropic amount of water, e.g., at least 4 wt. %, preferably less than 20 wt. %, e.g., less than 12 wt. % or less than 7.5 wt. %. Water may be removed from the second distillate in line  175  using several different separation techniques as described herein. Particularly preferred techniques include the use of distillation column, membranes, adsorption units, and combinations thereof. 
     Some of the residues withdrawn from the separation systems shown in  FIGS. 1-3 , may comprise acetic acid, higher acid, and water. Depending on the amount of water, acetic acid and higher acid contained in the residue of first column, e.g.,  150  in  FIG. 2 , or residue of second column  173  in  FIG. 3 , the residue may be treated in one or more of the following processes. 
     The following are exemplary processes for further treating the residue and it should be understood that any of the following may be used regardless of acid concentration. When the residue comprises a majority of acetic acid and heavier acid, e.g., greater than 70 wt. %, the residue may be recycled to the reactor without any separation of the water. In one embodiment, the residue may be separated into an acid stream and a water stream when the residue comprises a majority of acetic acid and heavier acid, e.g., greater than 50 wt. %. Acid may also be recovered in some embodiments from the residue having a lower acid concentration. The residue may be separated into the acid and water streams by a distillation column or one or more membranes. If a membrane or an array of membranes is employed to separate the acid from the water, the membrane or array of membranes may be selected from any suitable acid resistant membrane that is capable of removing a permeate water stream. The resulting acid stream comprising acetic acid and heavier acid optionally is returned to the first reaction zone  102 . The resulting water stream may be used as an extractive agent or to hydrolyze an ester-containing stream in a hydrolysis unit. 
     In other embodiments, for example, where the residue comprises less than 50 wt. % acid, possible options include one or more of: (i) returning a portion of the residue to reactor  103 , (ii) neutralizing the acid, (iii) reacting the acid with an alcohol, or (iv) disposing of the residue in a waste water treatment facility. It also may be possible to separate a residue comprising less than 50 wt. % acid using a weak acid recovery distillation column to which a solvent (optionally acting as an azeotroping agent) may be added. Exemplary solvents that may be suitable for this purpose include ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, vinyl acetate, diisopropyl ether, carbon disulfide, tetrahydrofuran, isopropanol, ethanol, and C 3 -C 12  alkanes. When neutralizing the acid, it is preferred that the residue comprises less than 10 wt. % acid (acetic acid and higher acid in combination). The acid may be neutralized with any suitable alkali or alkaline earth metal base, such as sodium hydroxide or potassium hydroxide. When reacting acid with an alcohol, it is preferred that the residue comprises less than 50 wt. % acid. The alcohol may be any suitable alcohol, such as methanol, ethanol, propanol, butanol, or mixtures thereof. The reaction forms an ester that may be integrated with other systems, such as carbonylation production or an ester production process. Preferably, the alcohol comprises ethanol and the resulting ester comprises ethyl acetate. Optionally, the resulting ester may be fed to the hydrogenation reactor. 
     In some embodiments, when the residue comprises very minor amounts of acid, e.g., less than 5 wt. %, the residue may be disposed of to a waste water treatment facility without further processing. The organic content, e.g., acid content, of the residue beneficially may be suitable to feed microorganisms used in a waste water treatment facility. 
     The columns shown in figures may comprise any distillation column capable of performing the desired separation and/or purification. Each column preferably comprises a tray column having from 1 to 150 trays, e.g., from 10 to 100 trays, from 20 to 95 trays or from 30 to 75 trays. The trays may be sieve trays, fixed valve trays, movable valve trays, or any other suitable design known in the art. In other embodiments, a packed column may be used. For packed columns, structured packing or random packing may be employed. The trays or packing may be arranged in one continuous column or they may be arranged in two or more columns such that the vapor from the first section enters the second section while the liquid from the second section enters the first section, etc. 
     The associated condensers and liquid separation vessels that may be employed with each of the distillation columns may be of any conventional design and are simplified in the figures. Heat may be supplied to the base of each column or to a circulating bottom stream through a heat exchanger or reboiler. Other types of reboilers, such as internal reboilers, may also be used. The heat that is provided to the reboilers may be derived from any heat generated during the process that is integrated with the reboilers or from an external source such as another heat generating chemical process or a boiler. Although one reactor and one flasher are shown in the figures, additional reactors, flashers, condensers, heating elements, and other components may be used in various embodiments of the present invention. As will be recognized by those skilled in the art, various condensers, pumps, compressors, reboilers, drums, valves, connectors, separation vessels, etc., normally employed in carrying out chemical processes may also be combined and employed in the processes of the present invention. 
     The temperatures and pressures employed in the columns may vary. As a practical matter, pressures from 10 kPa to 3000 kPa will generally be employed in these zones although in some embodiments subatmospheric pressures or superatmospheric pressures may be employed. Temperatures within the various zones will normally range between the boiling points of the composition removed as the distillate and the composition removed as the residue. As will be recognized by those skilled in the art, the temperature at a given location in an operating distillation column is dependent on the composition of the material at that location and the pressure of column. In addition, feed rates may vary depending on the size of the production process and, if described, may be generically referred to in terms of feed weight ratios. 
     The final alcohol product produced by the processes of the present invention may be taken from a stream that primarily comprises ethanol and/or heavier alcohols from  FIGS. 1-3 . The alcohol product may be an industrial grade ethanol composition comprising from 75 to 96 wt. % ethanol, e.g., from 80 to 96 wt. % or from 85 to 96 wt. % ethanol, based on the total weight of the ethanol product. Depending on the embodiment of the invention, the finished alcohol product may include a minor or a substantial amount of heavier alcohols, or may be substantially free of any heavier alcohols if, for example, the heavier alcohols are separated from the ethanol during processing. Non-limiting exemplary finished alcohol compositional ranges are provided below in Table 11. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 FINISHED ALCOHOL COMPOSITIONS 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Conc. 
                 Conc. 
                 Conc. 
                 Conc. 
                 Conc. 
               
               
                 Component 
                 (wt. %) 
                 (wt. %) 
                 (wt. %) 
                 (wt. %) 
                 (wt. %) 
               
               
                   
               
               
                 Ethanol 
                   75 to 99.9 
                   80 to 99.5 
                 85 to 96 
                 85 to 96 
                 85 to 96 
               
               
                 Heavier 
                 0.01 to 20   
                 0.04 to 20   
                 0.5 to 10  
                 1 to 8 
                 2 to 5 
               
               
                 Alcohol* 
               
               
                 Water 
                 &lt;12 
                 1 to 9 
                 3 to 8 
                 3 to 8 
                 3 to 8 
               
               
                 Acetic Acid 
                 &lt;1 
                 &lt;0.1 
                 &lt;0.01 
                 &lt;0.01 
                 &lt;0.01 
               
               
                 Heavier 
                 &lt;1 
                 &lt;0.1 
                 &lt;0.01 
                 &lt;0.01 
                 &lt;0.01 
               
               
                 Acid** 
               
               
                 Ethyl 
                 &lt;2 
                 &lt;0.5 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
               
               
                 Acetate 
               
               
                 Acetal 
                 &lt;0.05 
                 &lt;0.01 
                 &lt;0.005 
                 &lt;0.005 
                 &lt;0.005 
               
               
                 Acetone 
                 &lt;0.05 
                 &lt;0.01 
                 &lt;0.005 
                 &lt;0.005 
                 &lt;0.005 
               
               
                   
               
            
           
         
       
     
     As discussed above, although in some embodiments the finished alcohol composition may comprise a substantial amount of higher alcohols, in some embodiments, the finished ethanol composition of the present invention contains very low amounts, e.g., less than 0.5 wt. %, of other alcohols, such as methanol, butanol, n-propanol, isobutanol, isoamyl alcohol and other higher alcohols. In one embodiment, the amount of isopropanol in the finished alcohol composition is from 80 to 1,000 wppm, e.g., from 95 to 1,000 wppm, from 100 to 700 wppm, or from 150 to 500 wppm. In one embodiment, the finished alcohol composition is substantially free of acetaldehyde, optionally comprising less than 8 wppm acetaldehyde, e.g., less than 5 wppm or less than 1 wppm. 
     In some embodiments, when further water separation is used, the alcohol product may be withdrawn as a stream from the water separation unit as discussed above. In such embodiments, the ethanol concentration of the alcohol product may be greater than indicated in Table 11, and may be greater than 97 wt. % ethanol, e.g., greater than 98 wt. % or greater than 99.5 wt. %. The alcohol product in this aspect preferably comprises less than 3 wt. % water, e.g., less than 2 wt. % or less than 0.5 wt. %. 
     Denatured Ethanol Compositions 
     As noted above, the alcohol composition formed by the processes of the invention may constitute a denatured ethanol composition comprising ethanol and at least one, e.g., at least two or at least three, denaturants. The denaturant may be produced in situ via the hydrogenation reaction, thus eliminating the need for an outside denaturant source. Preferably, the denaturant comprises one or more heavier alcohols, preferably comprising propanol, formed from the hydrogenation of one or more heavier acids, preferably comprising propionic acid. Additionally, the denaturant may comprise one or more of ethyl acetate, acetaldehyde, diethyl ether, acetic acid, isopropanol and/or mixtures thereof. 
     The denaturant, thus produced, should be present in an effective amount, e.g., in an amount sufficient to provide for a denatured ethanol composition in accordance with appropriate government regulations. As used herein, the term “denatured ethanol composition” means a composition comprising ethanol and one or more denaturants that is unfit for beverage or internal human medicine, e.g., unpalatable. In other embodiments, the denatured ethanol may comprise a “specifically denatured ethanol,” which is an ethanol composition that is denatured pursuant to the formulae authorized under 27 C.F.R. Part 21, Subpart D. In addition, requirements for denatured ethanols are different for different applications, e.g., fuel applications and industrial applications. Thus, some applications may require higher amounts of denaturants while other applications may require lower amounts. Fuel uses for ethanol may necessitate supplementing the denatured mixed alcohol composition of the invention with one or more fuel denaturants that are suitable for fuel uses. Such fuel denaturants may vary depending on country and region, but some examples include natural gasoline, gasoline blendstocks or unleaded gasoline. A listing of some of these applications is provided in 27 C.F.R. Part 21, the entirety of which is incorporated herein by reference. Table 12 indicates some of the denatured compositions in terms of the amount of denaturant that is added to 100 gallons of ethanol. 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 US Denatured Alcohol Formulae According to 27 C.F.R. Part 21 
               
            
           
           
               
               
               
            
               
                   
                   
                 Amount 
               
               
                 Formula 
                 Denaturant 
                 (gallons) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Formula 3-C 
                 isopropyl alcohol 
                 5 
               
               
                 Formula 13-A 
                 ethyl ether 
                 10 
               
               
                 Formula 18* 
                 vinegar 90-grain strength (9% acetic acid in 
                 100 
               
               
                   
                 water) 
               
               
                 Formula 18* 
                 vinegar 60-grain strength (6% acetic acid in 
                 150 
               
               
                   
                 water) 
               
               
                 Formula 29 
                 acetaldehyde 
                 1 
               
               
                 Formula 29 
                 alcohol solution containing not less than 
                 5 
               
               
                   
                 20% acetaldehyde 
               
               
                 Formula 29 
                 ethyl acetate 
                 1 
               
               
                 Formula 32 
                 ethyl ether 
                 5 
               
               
                 Formula 35 
                 ethyl acetate 
                 29.75 
               
               
                 Formula 35 
                 mixture of ethyl acetate with an ester 
                 35 
               
               
                   
                 content of not less than 
               
               
                   
                 85 percent by weight 
               
               
                 Formula 35-A 
                 ethyl acetate 
                 4.25 
               
               
                 Formula 35-A 
                 mixture of ethyl acetate with an ester 
                 5 
               
               
                   
                 content of not less than 
               
               
                   
                 85 percent by weight 
               
               
                   
               
               
                 *Ethanol is not less than 160 proof. 
               
            
           
         
       
     
     In addition, in other embodiments, the inventive denatured ethanol compositions, as formed, correspond to the denatured formulae of countries other than the United States. For example, in the United Kingdom, one formula for trade specific denatured alcohol is as follows. With every 979 parts by volume of alcohol (of a strength of not less than 85 percent alcohol by volume) mix not less than 20 parts by volume of ethyl acetate and 1 part by volume of isopropyl alcohol. 
     Another exemplary United Kingdom trade specific denatured alcohol formula is as follows. With every 950 parts by volume of alcohol (of a strength of not less than 85 percent alcohol by volume) mix not less than 50 parts by volume of isopropyl alcohol. 
     Of course, this listing of US and international denatured ethanol composition formulae is not exclusive and other formula are within the scope of the invention. 
     Preferably, the denatured ethanol composition comprises from 50 wt. % to 99 wt. % ethanol, e.g., from 60 wt. % to 99 wt. % or from 70 wt. % to 95 wt. %, and from 0.01 wt. % to 40 wt. % denaturant, e.g., from 0.01 wt. % to 25 wt. %, from 0.01 wt. % to 20 wt. %, or from 1 wt. % to 15 wt. %, based on the total weight of the denatured ethanol composition. 
     In some embodiments, the inventive denatured ethanol composition comprises at least a portion of the first column distillate of  FIG. 1A-C , as discussed above. Here, the denatured ethanol composition may comprise as the denaturant ethyl acetate and/or acetaldehyde. Preferably, the amount of total denaturant (ethyl acetate and acetaldehyde) in these denatured ethanol compositions ranges from 0.01 wt. % to 90 wt. % denaturant, e.g., from 0.01 wt. % to 65 wt. % or from 0.01 wt. % to 34 wt. %. 
     In some embodiments, the ethanol composition comprises an ethyl ether, e.g., diethyl ether, denaturant in an amount ranging from 0.1 wt. % to 20 wt. % diethyl ether, e.g., from 0.1 wt. % to 10 wt. %, from 1 wt. % to 9 wt. % or from 3 wt. % to 7 wt. %. In other embodiments, the ethanol composition comprises an acetic acid denaturant in an amount ranging from 0.1 wt. % to 20 wt. % acetic acid, e.g., from 1 wt. % to 15 wt. % or from 2 wt. % to 12 wt. %. In other embodiments, the ethanol composition comprises a heavier alcohol denaturant, such as n-propanol, in an amount ranging from 0.001 wt. % to 10 wt. % n-propanol, e.g., from 0.001 wt. % to 0.1 wt. %, from 0.1 wt. % to 10 wt. %, from 1 wt. % to 9 wt. %, or from 3 wt. % to 7 wt. %. 
     In preferred embodiments, the denatured ethanol composition is formed by combining a crude alcohol product derivative stream comprising denaturant, e.g., the second distillate, and a purified mixed alcohol stream, which comprises ethanol and one or more heavier alcohols. Exemplary weight percentage ranges for the ethanol, heavier alcohol(s) and the denaturants, e.g., ethyl acetate and/or acetaldehyde, (as well as other optional components) are provided in Table 13. In some embodiments, the ethanol composition comprises an ethyl acetate denaturant in an amount ranging from 0.01 wt. % to 40 wt. % ethyl acetate, e.g., from 0.01 wt. % to 15 wt. %, from 0.01 wt. % to 10 wt. % or from 0.01 wt. % to 9 wt. %. In other embodiments, the denatured ethanol composition comprises an acetaldehyde denaturant in an amount ranging from 0.01 wt. % to 10 wt. % acetaldehyde, e.g., from 0.01 wt. % to 5 wt. %, from 0.01 wt. % to 2 wt. % or from 0.01 wt. % to 1 wt. %. Preferably, the amount of total denaturant in these denatured ethanol compositions ranges from 0.01 wt. % to 20 wt. % denaturant, e.g., from 0.01 wt. % to 12 wt. % or from 0.01 wt. % to 10 wt. %. 
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 DENATURED ETHANOL COMPOSITIONS 
               
            
           
           
               
               
               
               
            
               
                 Component 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
                 Conc. (wt. %) 
               
               
                   
               
               
                 Ethanol 
                   50 to 99 
                 60 to 99 
                 70 to 95 
               
               
                 Water 
                 0.0001 to 1   
                 0.001 to 0.1  
                 0.001 to 0.05  
               
               
                 Acetic Acid 
                   1 to 20 
                  3 to 15 
                   5 to 10.5 
               
               
                 Higher Acid** 
                 &lt;10 
                 0.01 to 5   
                 0.1 to 2   
               
               
                 Heavier Alcohol* 
                 0.01 to 20 
                 0.04 to 20   
                 0.5 to 10  
               
               
                 (Denaturant) 
               
               
                 Ethyl Acetate 
                 &lt;15 
                 &lt;10 
                 &lt;9 
               
               
                 (Denaturant) 
               
               
                 Acetaldehyde 
                 &lt;10 
                 &lt;5 
                 &lt;3 
               
               
                 (Denaturant) 
               
               
                 Isopropanol 
                 0.05 to 10 
                 0.6 to 9   
                   2 to 6.7 
               
               
                 (Denaturant) 
               
               
                 Diethyl Ether 
                 0.05 to 10 
                 0.6 to 9   
                   2 to 6.7 
               
               
                 (Denaturant) 
               
               
                 N-propanol 
                 0.05 to 10 
                 0.6 to 9   
                   2 to 6.7 
               
               
                 (Denaturant) 
               
               
                 Acetal 
                 &lt;0.05 
                 &lt;0.01 
                 &lt;0.005 
               
               
                 Acetone 
                 &lt;0.05 
                 &lt;0.01 
                 &lt;0.005 
               
               
                   
               
            
           
         
       
     
     Although the exemplary weight percentages of water in the embodiments of Table 13 range from 0.0001 wt. % to 1 wt. %, in other embodiments, water may be present in the denatured ethanol composition in greater amounts. For example, the denatured ethanol composition may comprise water in an amount ranging from 0.1 wt. % to 8 wt. % water, e.g., from 0.1 wt. % to 5 wt. % or from 0.1 wt. % to 2 wt. %. 
     The denatured ethanol compositions of the embodiments of the present invention may be suitable for use in a variety of applications including fuels, solvents, chemical feedstocks, pharmaceutical products, cleansers, sanitizers, or hydrogenation transport. In fuel applications, the denatured ethanol composition may be blended with gasoline for motor vehicles such as automobiles, boats and small piston engine aircrafts. In non-fuel applications, the denatured ethanol composition may be used as a solvent for toiletry and cosmetic preparations, detergents, disinfectants, coatings, inks, and pharmaceuticals. The denatured ethanol composition may also be used as a processing solvent, e.g., in manufacturing processes for medicinal products, food preparations, dyes, photochemicals and latex processing. 
     The denatured ethanol composition may also be used as a chemical feedstock to make other chemicals such as vinegar, ethyl acrylate, ethyl acetate, ethylene, glycol ethers, ethylamines, aldehydes, and higher alcohols, especially butanol. The denatured ethanol composition may be suitable for use as a feed stock in esters production. Preferably, in the production of ethyl acetate, the denatured ethanol composition may be esterified with acetic acid or reacted with polyvinyl acetate. The denatured ethanol composition may be dehydrated to produce ethylene. Any of known dehydration catalysts can be employed to dehydrate ethanol, such as those described in copending U.S. application Ser. No. 12/221,137 and U.S. application Ser. No. 12/221,138, the entire contents and disclosures of which are hereby incorporated by reference. A zeolite catalyst, for example, may be employed as the dehydration catalyst. Preferably, the zeolite has a pore diameter of at least about 0.6 nm, and preferred zeolites include dehydration catalysts selected from the group consisting of mordenites, ZSM-5, a zeolite X and a zeolite Y. Zeolite X is described, for example, in U.S. Pat. No. 2,882,244 and zeolite Y in U.S. Pat. No. 3,130,007, the entireties of which are hereby incorporated by reference. 
     While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those of skill in the art. In view of the foregoing discussion, relevant knowledge in the art and references discussed above in connection with the Background and Detailed Description, the disclosures of which are all incorporated herein by reference. In addition, it should be understood that aspects of the invention and portions of various embodiments and various features recited below and/or in the appended claims may be combined or interchanged either in whole or in part. In the foregoing descriptions of the various embodiments, those embodiments which refer to another embodiment may be appropriately combined with other embodiments as will be appreciated by one of skill in the art. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.