Patent Publication Number: US-7211702-B2

Title: Process for production of alcohols

Description:
This application is a divisional of U.S. patent application Ser. No. 09/918,474 filed on Aug. 1, 2001 now U.S. Pat. No. 6,833,483. 
    
    
     FIELD OF THE INVENTION 
     A first aspect of the present invention relates to a process for production of alcohols, and in particular to a process for the catalytic hydration of an olefin to the corresponding alcohol. 
     A second aspect of the present invention relates to a process for dehydration of an azeotropic mixture including a first alcohol and water to produce the first alcohol in a substantially anhydrous state. 
     BACKGROUND OF THE INVENTION 
     Several processes are known for the conversion of ethylene, higher olefins, and combinations of olefins to the corresponding alcohol by a hydration reaction. Typically, the hydration reaction produces a product mixture comprising an alcohol and an ether, each having the same carbon chain length as the olefin, in equilibrium with the olefin and water or steam. The thermodynamics and hence the equilibrium of the hydration reaction is such that formation of the alcohol and ether product mixtures is more favourable at low temperatures and high pressures. The attainment of the equilibrium is promoted through the use of a hydration catalyst. Capital and operating costs are lower when the hydration reaction is performed under mild conditions, however the equilibrium amount of the alcohol in the reaction mixture at low temperature and pressure is lower than the equilibrium amount of alcohol in the reaction mixture at low temperature and high pressure. 
     Examples of such prior art processes include Rolf-Rainer et al. in U.S. Pat. No. 4,760,203, issued in 1988, which describes the production of isopropanol, also known as IPA or 2-propanol or isopropyl alcohol, by hydration of a propene-containing hydrocarbon stream using an acidic cation exchange resin catalyst and a series of interconnected reactors in series. In each of the reactors an aqueous stream and a parallel hydrocarbon stream flow in opposite directions, thereby effecting separation of a product isopropanol rich stream from the reaction mixture. Dettmar et al. in U.S. Pat. No. 4,760,202, issued in 1988, describe the hydration of isoolefins having 4 or 5 carbon atoms to produce tertiary alcohols using a counterflow process and a hydration catalyst. Ramachandran and Dao in U.S. Pat. No. 5,488,185, issued in 1996, describe the hydration of an olefin in a mixture with an alkane to the corresponding alcohol in the presence of a hydration catalyst. Schmidt in U.S. Pat. No. 4,469,903, issued in 1984, describes a process for the production of an aliphatic alcohol, and in particular isopropanol, by the direct hydration of an olefinic hydrocarbon. The product alcohol in the equilibrium mixture is recovered from a water-rich hydration zone effluent stream by countercurrent liquid-liquid extraction against a paraffinic solvent. 
     Smith, Jr. in U.S. Pat. No. 5,221,441, issued in 1993, describes a method for operating a distillation process for three particular chemical production processes. One of said processes is the production of tertiary butanol, also known as tertiary butyl alcohol, by the hydration of isobutene, also known as 2-methylpropene or isobutylene, using an acid cation exchange resin. The acid cation exchange resin must be maintained in a wetted state by contact with water present in a liquid phase to maintain catalytic selectivity. When the acid cation exchange catalyst is not in contact with the liquid phase the catalyst loses selectivity to tertiary butanol due to loss of water. 
     In each of the above processes the catalyst is characteristically a hydrophilic acidic hydration catalyst. Further, in each of the above processes the product is wet, and at least one additional refining step is required for recovery of anhydrous liquid product. 
     Recovery of an alcohol in a substantially anhydrous state from an azeotropic mixture with water is an expensive and complex component of many industrial processes for the production of the alcohol. 
     As described above, several processes are known for the conversion of an olefin to the corresponding alcohol by a hydration reaction. Typically, the hydration reaction produces an alcohol, or a product mixture comprising a mixture of said alcohol and an ether, the alcohol and the ether each having the same carbon chain length as the olefin, in equilibrium with the olefin and water. The thermodynamics and hence the equilibrium of the hydration reaction is such that formation of the alcohol is more favorable at low temperatures and high pressures. The attainment of the equilibrium is promoted through use of a hydration catalyst. Although capital and operating costs are lower when the hydration reaction is performed under mild conditions, the equilibrium amount of the alcohol in the reaction mixture at low pressures is lower than the equilibrium amount of alcohol in the reaction mixture at high pressures. Several catalysts having acidic properties are useful for the hydration of an olefin to the corresponding alcohol. Said catalysts include acidic cation exchanged resins, inorganic acids and acids supported on inorganic supports. All such prior art catalysts are hydrophilic. 
     Alcohols are often sold in different grades, depending on the level of water they contain. For example, industrial ethanol has approximately 96.5% (vol) ethanol, the balance being water and a small amount of crude pyridine to “denature” the material, and sometimes a colouring agent. Denatured spirit has 88% (vol) ethanol, water and denaturing compounds. Fine alcohol (96.0–96.5% vol ethanol) is not denatured because it is used in preparation of pharmaceuticals, cosmetics and products for human consumption. Absolute alcohol must have at least 99.7–99.8% vol ethanol, and is used in the preparation of pharmaceuticals and products for human consumption. Normally, absolute alcohol is sold with over 99.9% vol ethanol. Conventional processes for production of ethanol, isopropanol and other alcohols by hydration of an olefin produce a product mixture containing both said alcohol and water. Therefore several methods have been developed by which fine or absolute grades of the alcohol can be recovered from the product mixture. Each such method is costly, with the consequence that fine and absolute grades of alcohol are significantly more expensive to produce than grades containing higher amounts of water. 
     One prior art approach is to separate a product mixture containing an alcohol and water using a third liquid that selectively removes the alcohol from the product mixture by absorption of the alcohol in the third liquid. Examples of such processes for recovery of light alcohols are described by Rolf-Rainer et al. in U.S. Pat. No. 4,760,203, issued in 1988, by Dettmar et al. in U.S. Pat. No. 4,760,202, issued in 1988, and by Schmidt in U.S. Pat. No. 4,469,903, issued in 1984. 
     Another prior art approach is first to distill the alcohol from the product mixture as an azeotropic mixture containing said alcohol and water. The water is then removed from the azeotropic mixture by use of a third fluid that also forms an azeotropic mixture with water. The volatile third component is added to the azeotropic mixture of alcohol and water. The mixture is then separated by distillation, the third component forming an azeotropic mixture with water that has a boiling point lower than a boiling point of the azeotropic mixture of the alcohol and water. The third component and the water are thereby distilled from the mixture to leave the alcohol as a liquid product having a water content lower than a water content of the original azeotropic mixture. Separation of azeotropic mixtures is described, for example, by Hoffman in  Azeotropic and Extractive Distillation, Interscience Library of Chemical Engineering and Processing , John Wiley and Sons, New York (1964), pages 165–168 and 179–203 and by Wankat in  Equilibrium Staged Separations , Elsevier, New York (1988). 
     Normally, hydration under mild conditions of an olefin having a carbon chain length of at least 4 carbon atoms produces the corresponding alcohol, but only negligible or undetectably small amounts of the corresponding ether. Linnekoski et al. in Applied Catalysis A: General, vol. 170 (1998), pages 117–126, measured and compared the activation energies for hydration of isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) to form 2-methyl-2-butanol (t-amyl alcohol) and etherification of the same isoamylenes with ethanol to form ethyl (2-methyl-2-butyl) ether (ethyl t-amyl ether). The activation energy for the etherification reaction was 117.7 kJ.mol-1, which value is considerably greater than the activation energy for the hydration reaction of the same olefins to 2-methyl-2-butanol, 79.9 kJ.mol-1. Thus it is to be expected that there will be negligibly small conversion of 2-methyl-2-butenes to di-(2-methyl-2-butyl) ether (di-t-amyl ether) during hydration of 2-methyl-2-butenes to 2-methyl-2-butanol under mild conditions 
     SUMMARY OF THE INVENTION 
     The first aspect of the invention provides a process by which an olefin can be hydrated to produce a corresponding alcohol under mild conditions, more efficiently and more economically than can be achieved using the prior art processes. It is desirable that the alcohol is recovered as a substantially anhydrous product. It is even more desirable that the alcohol is recovered as a substantially anhydrous liquid product. The present invention provides a process for the continuous and simultaneous catalytic hydration of an olefin under mild conditions to a reaction mixture containing the corresponding alcohol and recovery of the alcohol as a substantially anhydrous liquid product from the reaction mixture. 
     The second aspect of the invention provides a process by which water can be removed easily from an azeotropic mixture of an alcohol and water to allow recovery of the corresponding substantially anhydrous alcohol under mild conditions, more efficiently and more economically than can be achieved using the prior art processes. This aspect of the present invention provides a process for the continuous removal of the water content of an azeotropic mixture containing a first alcohol and water by catalytic hydration of an olefin under mild conditions to a corresponding second alcohol, with simultaneous and continuous removal of the first alcohol and the second alcohol from the reaction mixture. In one embodiment, the hydration reaction is carried out using a solid phase hydration catalyst e.g. in a catalytic distillation column that serves simultaneously as a reactor and as a distillation column. 
     According to one embodiment of the invention, a process for producing an alcohol is provided, comprising:
     a) subjecting an olefin to a hydration reaction with water to form a reaction product including the corresponding alcohol, the olefin having a carbon chain length in the range of 2 to 12 carbon atoms, the carbon chain being selected from a linear chain, a branched chain and a chain having a cyclic hydrocarbon component, the reaction being conducted in the presence of a solid state olefin hydration catalyst, the temperature and pressure of the hydration reaction being selected so that the olefin is largely in a vapour phase and the alcohol is in the liquid phase the olefin being in a molar excess when compared with water, and   b) simultaneously recovering the alcohol as a substantially anhydrous liquid.   

     In some aspects of this embodiment of the invention, it is advantageous to employ a catalyst having hydrophobic properties. 
     In some cases, the hydration reaction is a catalytic distillation reaction, which can be effected in a distillation column, the olefin and water being continuously fed to the column. The catalyst may be disposed in a single catalyst bed or in several beds. As will be apparent below, there is advantage in providing exposure to the catalyst in two separate spaced apart beds. The beds may be fixed beds. The catalyst beds are typically disposed within the same reactor/distillation column. 
     Although not specifically described herein, it will be appreciated by those skilled in the art that the olefin may include a cyclic hydrocarbon component. 
     According to another embodiment of the invention, a process for reducing the water content of an azeotropic mixture of a first alcohol and water is provided, comprising:
     (a) effecting a hydration reaction of the water content of the azeotropic mixture with an olefin, wherein the olefin is hydrated to a corresponding second alcohol, the second alcohol being selected from the group consisting of the same alcohol as the first alcohol, an alcohol readily separable from the first alcohol by a distillation procedure, and an alcohol forming a useful mixture when mixed with the first alcohol, the hydration reaction of the olefin being conducted in the presence of a solid state hydration catalyst, the temperature and the pressure of the hydration reaction being selected so that the olefin is largely in the vapour phase and the first alcohol and the second alcohol are each largely in a liquid phase, the olefin being in a molar excess when compared with the water content of the azeotropic mixture, and   (b) continuously removing the first alcohol and the second alcohol as a substantially anhydrous liquid mixture.   

     The catalyst is typically disposed in at least two spaced apart catalyst beds. The catalytic beds are typically disposed within the same reactor/distillation column, although in some cases a pre-reactor with a bed and then a column having a bed, can be used. One bed will work, albeit not as well. 
     In some aspects of this embodiment of the invention, it is advantageous to employ a catalyst having hydrophobic properties. 
     In one aspect of this embodiment of the invention, the hydration reaction is a catalytic distillation reaction, which can be effected in a distillation column, the olefin and the azeotropic mixture being continuously fed to the column. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and the other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein: 
         FIG. 1  is a schematic diagram of a catalytic distillation process for hydration of an olefin to the corresponding alcohol, in which the catalytic distillation column has one catalyst bed. 
         FIG. 2  is a schematic diagram of a catalytic distillation column having one catalyst bed for the catalytic distillation process shown in  FIG. 1 . 
         FIG. 3  is a schematic diagram of a catalytic distillation process for hydration of an olefin to the corresponding alcohol, in which the catalytic distillation column has two catalyst beds. 
         FIG. 4  is a schematic diagram of a catalytic distillation column having two catalyst beds for the catalytic distillation process shown in  FIG. 3 . 
         FIG. 5 , labeled PRIOR ART, is a schematic diagram of the Tokyoyama process for hydration of propene to isopropanol, the process being an example of a conventional process for the production of an alcohol by hydration of an olefin. 
         FIG. 6  is a profile of the steady state composition of the components of the reaction mixture during hydration of propene to isopropanol at an operating pressure of 2 megaPascals in the catalytic distillation column having two catalyst beds shown in  FIG. 4 . 
         FIG. 7  is a profile of the steady state composition of the components of the reaction mixture during hydration of propene to isopropanol at an operating pressure of 4 megaPascals in the catalytic distillation column having two catalyst beds shown in  FIG. 4 . 
         FIG. 8  is a profile of the steady state composition of the components of the reaction mixture during hydration of isobutene to tertiary butanol at an operating pressure of 1.2 megaPascals in the catalytic distillation column having two catalyst beds shown in  FIG. 4 . 
         FIG. 9  is a schematic diagram showing the dimensions of the catalytic distillation column having one catalyst bed shown in  FIG. 2 , the temperatures at three positions, and the flow rates of the feed and exit streams for hydration of propene to isopropanol at a pressure of 2 megaPascals. 
         FIG. 10  is a schematic diagram showing the dimensions of the catalytic distillation column having one catalyst bed shown in  FIG. 2 , the temperatures at three positions, and the flow rates of the feed and exit streams for hydration of propene to isopropanol at a pressure of 4 megaPascals. 
         FIG. 11  is a schematic diagram showing the dimensions of the catalytic distillation column having two catalyst beds shown in  FIG. 4 , the temperatures at four positions, and the flow rates of the feed and exit streams for hydration of propene to isopropanol at a pressure of 2 megaPascals. 
         FIG. 12  is a schematic diagram showing the dimensions of the catalytic distillation column having two catalyst beds shown in  FIG. 4 , the temperatures at four positions, and the flow rates of the feed and exit streams for hydration of propene to isopropanol at a pressure of 4 megaPascals. 
         FIG. 13  is a schematic diagram showing the dimensions of the catalytic distillation column having two catalyst beds shown in  FIG. 4 , the temperatures at four positions, and the flow rates of the feed and exit streams for hydration of isobutene to tertiary butanol at a pressure of 1.2 megaPascals. 
         FIG. 14  is a schematic diagram of a catalytic distillation column for recovery of a first alcohol in a substantially anhydrous state from an azeotropic mixture containing both of the first alcohol and water, in which the catalytic distillation column has two catalyst beds. 
         FIG. 15  is a schematic diagram of a catalytic distillation process for the recovery of substantially anhydrous ethanol from the product stream from a distillation process for the production of an azeotropic mixture of ethanol and water, including the catalytic distillation shown in  FIG. 14 . 
         FIG. 16  is a profile of the composition of the components of the reaction mixture during the recovery of substantially anhydrous ethanol from an azeotropic mixture with water by the hydration of 2-methyl-2-butene at an operating pressure of 0.5 megaPascals, in the catalytic distillation column shown in  FIG. 14 . 
         FIG. 17  is a schematic diagram showing the dimensions of the catalytic distillation column having two catalyst beds shown in  FIG. 14 , the temperatures at four positions, and the flow rates of the feed and exit streams for recovery of ethanol from an azeotropic mixture containing water by hydration of 2-methyl-2-butene at an operating pressure of 0.5 megaPascals. 
         FIG. 18  is a schematic diagram of a catalytic distillation column for recovery of a first alcohol in a substantially anhydrous state from an azeotropic mixture containing both of the first alcohol and water shown in  FIG. 14 , in which a take off line for a side stream is fitted at the side of the column as a second system for recovery of liquid product. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the first aspect of the invention, the hydration reaction is carried out using a solid phase hydration catalyst in a catalytic distillation column that serves simultaneously as a reactor and as a distillation column. When a reaction product mixture is separated continuously by distillation simultaneously with the reaction, the process is termed “reactive distillation.” When a catalyst is used to catalyze the reaction occurring simultaneously with distillation the process is termed “catalytic distillation.” In the present invention an olefin and water are continuously fed to the catalytic distillation column. The reaction is performed at a temperature and a pressure selected so that the rate of the reaction is high, the olefin is in the vapour phase, and the alcohol corresponding to the olefin i.e. having the same linear or branched structure and the same number of carbon atoms is recoverable as a liquid product. The alcohol is continuously removed from the reaction mixture as a liquid product stream from the base of the catalytic distillation column. The operating conditions can be selected so that the alcohol content of the liquid product stream is over 99% and as high as 99.9%, i.e. the alcohol is recovered as a substantially anhydrous liquid product. Exemplary ranges for T and P are P=0.1–4 MPa and T=50–225° C.) 
     For example, hydration of ethylene produces ethanol and diethyl ether in an equilibrium reaction illustrated as Equation 1. Hydration of an olefin with more than two carbon atoms produces a corresponding secondary alcohol and an ether as illustrated in Equation 2 in which R represents an organic radical having one or more carbon atoms. The proportion of alcohol to ether in the equilibrium mixture depends on the reaction conditions and on the relative proportions of water and olefin in the reaction mixture.
 
C 2 H 4 +H 2 O⇄C 2 H 5 OH+(C 2 H 5 ) 2 O  (1)
 
RCH=CH 2 +H 2 O⇄RCH(OH)CH 3 +(RCHCH 3 ) 2 O  (2)
 
     The characteristics of a process by which amyl alcohol has been produced using a catalytic distillation column and AMBERLIST 15 as a catalyst have been studied by Gonzalez et al. ( Industrial and Engineering Chemistry Research,  1997, 36, 3845–3853). The study by Gonzalez et al. did not include an advantage of the present invention, which is described below. In particular, the present invention includes the advantages of using dual spaced apart catalyst beds, and use of a hydration catalyst having hydrophobic characteristics, that will now be described for the first time. 
     The equipment and method for the simultaneous hydration of an olefin to a corresponding secondary alcohol and recovery of the alcohol will now be described with reference to  FIGS. 1 through 5 . The invention will then be illustrated using a series of non-limiting examples to illustrate procedures and conditions applicable to specific alcohols, with reference to  FIGS. 1 through 13 . 
     The present invention provides a method for the continuous and simultaneous catalytic hydration of an olefin to a product mixture rich in an alcohol corresponding to the olefin, and removal of the product mixture rich in alcohol from the reaction mixture. A first embodiment of equipment  10  for said method for hydration of an olefin to the corresponding alcohol will be described with reference to  FIGS. 1 and 2 . A second embodiment of equipment  100  for said process will be described with reference to  FIGS. 3 and 4 . A component that is common to each of first embodiment of equipment  10  and second embodiment of equipment  100  will be identified using the same reference numeral. One PRIOR ART process for the hydration of an olefin to the corresponding alcohol is illustrated in  FIG. 5 , for purpose of comparison with the process of the present invention. 
     Referring to  FIG. 1 , first embodiment of equipment  10  for continuous and simultaneous hydration of an olefin to a corresponding alcohol and recovery of said alcohol as a liquid product comprises a catalytic distillation column  12 , an olefin feed system  14 , a water feed system  16 , a liquid product recovery system  18 , and a volatiles recovery system  20 . 
     Referring to  FIG. 2 , catalytic distillation column  12  has a body  22  having elongate cylindrical sidewalls  24 , a top  26  and a base  28  defining an interior cavity  30 . Body  22  is constructed of a material that is unaffected by the components of a reaction mixture contained within interior cavity  30 . Body  22  can be insulated so as to maintain and withstand a temperature at which a reaction is conducted within interior cavity  30 . Body  22  is capable of containing a pressurized reaction mixture at a pressure at which the reaction is conducted. Interior cavity  30  has a first portion  32 , a second portion  34 , and a third portion  36 . Second portion  34  serves as a reaction zone during a catalytic distillation process. At least one catalyst bed  40  is situated within second portion  34 . Catalyst bed  40  contains packed material comprising an active olefin hydration catalyst  42 . Rectification of the volatile components of the reaction mixture occurs in first portion  32  during the catalytic distillation process. First section  32  is sized so that heavier components of the mixture can be separated from unreacted volatiles and fall toward second section  34 . Third section  36  serves as a stripping section. Third section is sized so that an alcohol product  64  from the catalytic distillation process can be separated from a reaction mixture as a condensate and fall as a liquid  66  toward base  28 . 
     Referring to  FIG. 1 , olefins feed system  14  feeds an olefin  44  to catalytic distillation column  12 . Olefin  44  is fed under pressure in a direction indicated by arrows  46  via sequentially a first olefin feed line  48 , and a second olefin feed line  52  through sidewalls  24  into interior cavity  30  of body  22  of catalytic distillation column  12  at a position closely below catalyst bed  40 . Water feed system  16  includes a heat exchanger  60  whereby heat is recovered from liquids recovery system  18 . Water  54  is fed under pressure in a direction indicated by arrows  56  via sequentially a first water feed line  58 , heat exchanger  60 , and a second water feed line  62  through sidewalls  24  into interior cavity  30  at a position closely above catalyst bed  40 . Olefin  44  and water  54  react over catalyst  42  in catalyst bed  40  to produce a product mixture according to Equations 1 and 2. Referring to  FIG. 2 , the product mixture contains an alcohol  64  and an ether corresponding to olefin  44 . Alcohol  64  separates from the reaction mixture as a liquid  66  and is collected at third portion  36  of interior cavity  30 . A mixture comprising volatile components  68  of the reaction mixture separates from the reaction mixture and is collected at first portion  32  of interior cavity  30 . 
     Referring to  FIGS. 3 and 4 , second embodiment of equipment  100  includes a catalytic distillation column  112  having a first catalyst bed  140  and a second catalyst bed  240 , first catalyst bed  140  and second catalyst bed  240  being spaced apart. Referring to  FIG. 3 , olefin  44  is fed into interior cavity  130  at a position closely below first catalyst bed  140 . Water feed system  116  includes a first heat exchanger  160  and a second heat exchanger  260  whereby heat is recovered from liquid product recovery system  118 . Water  54  is fed into interior cavity  130  via water feed lines  162  and  262  at positions closely above each of first catalyst bed  140  and second catalyst bed  240  respectively. First catalyst bed  140  contains a packed material comprising a first active olefin hydration catalyst  142  and second catalyst bed  240  contains a packed material comprising a second active olefin hydration catalyst  242 . Second catalyst  242  optionally may be the same catalyst as first catalyst  142 . 
     Catalyst bed  40 , shown in  FIG. 2 , first catalyst bed  140  and second catalyst bed  240 , shown in  FIG. 4 , are each in the form of a fixed bed. Catalyst  42 , first catalyst  142  and second catalyst  242  each comprises a catalytic material having acidic properties. Conventional acidic catalysts active for hydration of an olefin to the corresponding alcohol are characteristically hydrophilic, and include: a cation exchange resin catalyst; a supported phosphoric acid catalyst; a catalyst comprising a heteropolyacid supported on a siliceous support; and a catalyst comprising a proton-exchanged form of a zeolite. In some embodiments, catalyst  42 , first catalyst  142  and second catalyst  242  each are hydrophobic e.g. SILICALITE and sulfate-treated SILICALITE. SILICALITE is a trademark for a commercially available silica (Union Carbide Inc.) having a highly regular crystallographic structure, the structure being characterized by a large surface area, and interconnected cavities within the regular structure. The more hydrophobic catalyst has the advantage that water does not compete with an olefin for active catalyst sites as readily as for the catalyst sites of conventional hydrophilic catalysts. A consequence is that water has a lower propensity to block access by the olefin to the active catalyst sites of the more hydrophobic catalyst when compared with more hydrophilic catalysts. The rate of the olefin hydration reaction thereby is enhanced. It will be recognized that other hydrophobic catalysts can be used without departing from the spirit of the present invention. The acidity, and hence the activity, and the selectivity of the catalyst can be altered by depositing additional materials selected from olefin hydration catalysts and promoters on SILICALITE. The use of a more hydrophobic catalyst overcomes the limitation on reaction rate caused by the low solubility of olefins in water, without the need for intervention of a co-solvent as described by Marker et al. in U.S. Pat. No. 5,744,645. 
     Referring to  FIGS. 1 through 4 , liquid  66  rich in alcohol  64  is withdrawn from base  28  in a direction indicated by an arrow  70  via a first liquid product line  72 . Referring to  FIG. 1 , liquid product recovery system  18  normally includes a reboiler  73  and a volatiles return line  75 . Liquid  66  is heated in reboiler  73 . A volatile fraction from heated liquid  66  is returned in a direction  77  from reboiler  73  through first return line  75  to third portion  36  of interior cavity  30 . Substantially pure alcohol  65  is recovered as liquid product from reboiler  73  in a direction indicated by arrows  79  via sequentially a second liquid product line  74 , heat exchanger  60 , and a third liquid product line  78 . Referring to  FIG. 3 , liquid product recovery system  118  also normally includes a reboiler  73  and a volatiles return line  75 . Substantially pure alcohol  65  is recovered as liquid product from reboiler  73  in a direction indicated by arrows  79  via sequentially second liquid product line  74 , first heat exchanger  160 , a fourth liquid product line  178 , second heat exchanger  260 , and a fifth liquid product line  278 . 
     Referring to  FIGS. 1 through 4 , a reaction mixture  68  comprising volatile components of the reaction mixture in catalytic distillation column  12  is withdrawn from top  24  of catalytic distillation column  12  via a volatiles line  80  in a direction indicated by an arrow  81 . Referring to  FIGS. 1 and 3 , volatiles recovery system  20  normally includes a condenser  83  and a liquids return line  85 . Reaction mixture  68  is condensed in condenser  83  to volatile liquids  87 . A first portion of volatile liquids  87  is returned in a direction indicated by an arrow  89  to first portion  32  of interior cavity  30  through liquids return line  85 . A second portion of volatile liquids  87  is recovered via volatile liquids recovery line  91  in a direction indicated by an arrow  93 . 
     Volatile liquids  87  are rich in olefin  44 . Second portion of volatile liquids  87  is optionally directed to an olefin recovery plant  84  where the stream is separated into an olefin-rich fraction and an alkane-rich fraction. The olefin-rich fraction is recycled to catalytic distillation column  12  in a direction indicated by arrow  86  via olefin recycle line  88  and second olefin feed line  52 . 
     The present invention confers advantages over the PRIOR ART, as will now be shown through the example of hydration of propene to isopropanol. Hydration of propene to isopropanol using existing technology is accomplished by one of several different processes. The performance of these processes is characterized as presented in TABLE 1. In TABLE 1 data are listed under headings A through E for the following PRIOR ART processes and under F for the process of the present invention: A: indirect hydration in one step; B: indirect hydration in two steps; C: fixed bed vapor phase direct hydration; D: trickle bed mixed phase direct hydration (Deutsche Texaco AG, as described in  Hydrocarbon Processing , November 1972, pages 113–116); E: liquid phase direct hydration (Tokyoyama Soda Co., Ltd.) illustrated in  FIG. 5 ; F: catalytic distillation according to the present invention using second embodiment of equipment  100  illustrated in  FIG. 3 . 
     Referring to TABLE 1, liquid  66  is richer in alcohol  64  when compared with a liquid product from a conventional process for production of the alcohol by hydration of the olefin. 
     Referring to  FIG. 5 , an example of the PRIOR ART is a process  300  operated by the Tokyoyama company for the production of isopropanol. In common with the process of the present invention, PRIOR ART process  300  has a propene feed system  302 , a water feed system  304  and a reactor  306 . The product is an aqueous mixture from which isopropanol is to be recovered. The product mixture from reactor  306  is fed sequentially to a separator  308 , an azeo column  310 , a light end recovery column  312 , a dehydration column  314 , and an isopropanol recovery column  316 , each of which is supported by appropriate valves and pressure and temperature controllers. A comparison of  FIG. 5  with  FIGS. 1 and 3  shows the greater complexity and consequent capital costs of PRIOR ART process  300  when compared with the present invention. 
     According to the second aspect of the present invention an olefin and an azeotropic mixture comprising the first alcohol and water are continuously fed to a catalytic distillation column. A hydration reaction is performed between the water in the azeotropic misture and an added olefin. The hydration reaction is performed at a temperature and a pressure selected so that: the rate of the hydration reaction is high; conversion of the olefin to the corresponding second alcohol is favored over conversion to the corresponding ether, and etherification of the olefin does not occur to a measurable degree; the olefin is largely in the vapour phase; and a liquid product mixture comprising the first alcohol and the second alcohol is produced. The first alcohol and the second alcohol are continuously removed as a liquid product stream from the base of the catalytic distillation column. These operating conditions provide for an alcohol content of the liquid product stream of over 99%. 
     A typical temperature range is 70–180° C. 
     A typical pressure range is 0.25–2.5 MPa. 
     A first embodiment of the equipment and an advantageous method for the simultaneous hydration of an olefin to a corresponding secondary alcohol and recovery of the alcohol will now be described with reference to  FIGS. 14 through 17 . A second embodiment of the equipment will be described with reference to  FIG. 18 . The invention will then be illustrated using non-limiting examples to illustrate procedures and conditions applicable to recovery of substantially anhydrous ethanol, with reference to  FIGS. 14 through 18 . 
     A first embodiment of equipment  410  for said method for hydration of an olefin to the corresponding alcohol will be described with reference to  FIGS. 14 and 15 . A second embodiment of equipment  500  will be described with reference to  FIG. 18 . One PRIOR ART process for the hydration of an olefin to the corresponding alcohol is illustrated in  FIG. 5 , for purpose of comparison of a conventional method for recovery of a substantially anhydrous alcohol with the method of the present invention. 
     Referring to  FIGS. 14 and 15 , first embodiment of equipment  410  for continuous and simultaneous removal of the water content of azeotropic mixture  412  containing first alcohol  414  and water  416  by hydration of an olefin  418  to a second alcohol  419  includes a catalytic distillation column  420 , an olefin feed system  422 , an azeotropic mixture feed system  424 , a liquid product recovery system  426 , and a volatiles recovery system  428 . 
     Referring to  FIG. 14 , catalytic distillation column  420  has a body  432  having elongate cylindrical sidewalls  434 , a top  436  and a base  438  defining an interior cavity  440 . Body  432  is constructed of a material that is unaffected by the components of a reaction mixture contained within interior cavity  440 . Body  432  can be insulated so as to maintain and withstand a temperature at which a reaction is conducted within interior cavity  440 . Body  432  is capable of containing a pressurized reaction mixture at a pressure at which the reaction is conducted. Interior cavity  440  has a first portion  442 , a second portion  444 , and a third portion  446 . Second portion  444  serves as a reaction zone during a catalytic distillation process. At least two catalyst beds  447 ,  448  that are in a vertically spaced-apart relationship are situated within second portion  444 . Catalyst beds  447 ,  448  contain packed material comprising an active olefin hydration catalyst  450 . Water  416  and olefin  418  react over catalyst  450  to produce second alcohol  419 . Rectification of the volatile components of the reaction mixture occurs in first portion  442  during the catalytic distillation process. First section  442  is sized so that heavier components of the mixture can be separated from unreacted volatiles and fall toward second section  444 . Third section  446  serves as a stripping section. Third section is sized so that ethanol  414  and second alcohol  419  can be separated from a reaction mixture as a condensate and fall as liquid  452  toward base  438 . 
     Olefin feed system  422  feeds olefin  418  to catalytic distillation column  412 . Olefin  418  is fed under pressure in a direction indicated by arrow  454  via an olefin feed line  456  through sidewalls  434  into interior cavity  440  of body  432  of catalytic distillation column  412  at a position closely below the lower catalyst bed  447 . Optionally, azeotropic mixture feed system  424  includes a heat exchanger (not illustrated) whereby heat is recovered from liquids recovery system  426 . Azeotropic mixture  412  is fed under pressure in a direction indicated by arrow  462  via sequentially an azeotropic mixture feed line  464  through sidewalls  434  into interior cavity  440  at a position closely above the lower catalyst bed  447 . Olefin  418  and water  416  from azeotropic mixture  412  react over catalyst  450  in catalyst beds  447 ,  448  to produce a product mixture containing both first alcohol  414  and second alcohol  419 . 
     Referring to  FIG. 15 , for purposes of example only, azeotropic mixture  412  can be the product from a distillation tower  4200  for separation of azeotropic mixture  412  from an aqueous alcohol stream  4202 . A water stream  4204  is separated as liquid at a bottom  4206  of tower  4200  from aqueous alcohol stream  4202 . Azeotropic mixture  412  is recovered as vapour at a top  4208  of tower  4200 . Said vapour is condensed in a condenser  4210  to form a liquid stream  4212 . Liquid stream  4212  is divided into a first fraction  4214  that is returned to tower  4200  and a second fraction  4216  that is azeotropic mixture  412  fed to column  420 . For example, when alcohol  414  is ethanol, industrial processes including fermentation can produce an aqueous solution containing approximately 10% ethanol. Said aqueous solution is separated by distillation in tower  4200  into water stream  4204  and a near azeotropic mixture comprising approximately 90% ethanol and 10% water. 
     Referring to  FIGS. 14 and 15 , first alcohol  414  and second alcohol  419  separate from the reaction mixture as liquid  452  and are collected at third portion  446  of interior cavity  440 . A mixture comprising volatile components  468  of the reaction mixture separates from the reaction mixture and is collected at first portion  442  of interior cavity  440 . 
     Catalyst beds  447 ,  448 , shown in  FIG. 15 , are fixed beds. Catalyst  450  comprises a catalytic material having acidic properties. Conventional acidic catalysts active for hydration of an olefin to the corresponding alcohol include: a cation exchanged resin catalyst as described by Gonzalez et al. and by Bezman; a supported phosphoric acid catalyst as described by Hoecker et al.; a catalyst comprising a heteropolyacid supported on a siliceous support as described by Haining et al.; and a catalyst comprising a proton-exchanged form of a zeolite as described by Wang et al. Preferably, catalyst  450  is more hydrophobic than a conventional olefin hydration catalyst. An example of a suitable hydrophobic olefin hydration catalyst is SILICALITE. SILICALITE is a trademark for a commercially available silica (Union Carbide Inc.) having a highly regular crystallographic structure, the structure being characterized by a large surface area, and interconnected cavities within the regular structure. We have also found that the catalytic activity increased significantly when the SILICALITE is sulfated e.g. with 1 N sulfuric acid. This results in a sulfated SILICALITE material. These catalysts confer advantages over conventional olefin hydration catalysts, as will now be described. The SILICALITE olefin hydration catalyst is more hydrophobic than conventional olefin hydration catalysts. The more hydrophobic catalyst has the advantage that water does not compete with an olefin for active catalyst sites as readily as for the catalyst sites of conventional catalysts. A consequence is that water has a lower propensity to block access by the olefin to the active catalyst sites of the more hydrophobic catalyst when compared with more hydrophilic catalysts. The rate of the olefin hydration reaction thereby is enhanced. It will be recognized that other similar hydrophobic olefin hydration catalysts can also be employed without departing from the spirit of the present invention. The acidity, and hence the activity, and the selectivity of the catalyst can be altered by depositing additional materials selected from olefin hydration catalysts and promoters on SILICALITE. The use of a more hydrophobic catalyst overcomes the limitation on reaction rate caused by the low solubility of olefins in a liquid azeotropic mixture, without the need for intervention of a co-solvent as described by Marker et al. 
     Referring to  FIGS. 14 and 15 , liquid  452  rich in first alcohol  414  and second alcohol  419  is withdrawn from base  438  in a direction indicated by an arrow  470  via a first liquid product line  472 . Referring to  FIG. 15 , liquid product recovery system  426  normally includes a reboiler  474  and a volatiles return line  476 . Liquid  452  is heated in reboiler  474 . A volatile fraction from heated liquid  452  is returned from reboiler  474  through first return line  476  to third portion  446  of interior cavity  440 . A substantially anhydrous mixture of first alcohol  414  and second alcohol  419  is recovered as liquid product from reboiler  474  in a direction indicated by arrows  480  via sequentially a second liquid product line  482 . 
     Referring to  FIG. 14 , a reaction mixture  468  comprising volatile components of the reaction mixture in catalytic distillation column  420  is withdrawn from top  436  of catalytic distillation column  412  via a volatiles line  486  in a direction indicated by an arrow  488 . Referring to  FIG. 15 , volatiles recovery system  428  normally includes a condenser  490  and a liquids return line  492 . Reaction mixture  468  is rich in unreacted olefin  418 , and also contains a substantial amount of alcohol  414 . Reaction mixture  468  is partly condensed in condenser  490  to volatile liquids. A first fraction  494  of reaction mixture  468  that is rich in unreacted olefin  418  and alcohol  414  is returned to first portion  432  of interior cavity  440  through liquids return line  492 . A second fraction  496  of reaction mixture  468  that is rich in alcohol  414  is recovered via volatiles recovery line  498  in a direction indicated by an arrow  4100 , and returned to tower  4200  for recovery of alcohol  414 . 
     A distillation process can separate first alcohol  414  and second alcohol  419  to the corresponding substantially pure (anhydrous) products, as illustrated in  FIG. 15 . Liquid product  452  is fed in direction  480  to an alcohol distillation column  4108 . When the process of the present invention is used to dehydrate a light first alcohol  414 , and olefin  418  is hydrated to form a heavier (higher molecular weight) second alcohol  419 , first alcohol  414  is recovered as a volatile fraction  4110  and second alcohol  419  is recovered as a bottom fraction  4112 . When first alcohol  414  is ethanol, and it is desired that said ethanol is to be separated from second alcohol  419  by distillation, it is necessary that olefin  418  has at least five carbon atoms. When olefin  418  is 2-methyl-2-butene, second alcohol  419  is 2-methyl-2-butanol. It is found that liquid product  452  contains no detectable amounts of ethyl (2-methyl-2-butyl) ether, which is consistent with the findings of the Linnekoski et al. reference. The boiling points of ethanol (78° C. at atmospheric pressure) and 2-methyl-2-butanol (102° C. at atmospheric pressure) are sufficiently far apart so as to allow separation by distillation in column  4108 . 
     Alternatively, olefin  418  can be selected so that first alcohol  414  and second alcohol  419  form a close boiling mixture point that is useful, for example as an additive for liquid automotive fuels. An example of a close boiling mixture is ethanol and 2-methyl-2-propanol (boiling point 82.5° C. at atmospheric pressure). The characteristics of a process by which amyl alcohol has been produced by reactive distillation over AMBERLIST 15 catalyst have been studied by Gonzalez et al. (Industrial and Engineering Chemistry Research, 1997, 36, 3845–3853). 
     Referring to  FIG. 18 , second embodiment of equipment  500  is similar to first embodiment of equipment  410 , with the difference that second embodiment of equipment  500  includes both of a first liquid product recovery system  526  that is substantially similar to liquid product recovery system  426  of first embodiment of equipment  410  and a second liquid product recovery system  502 . Second embodiment of equipment  500  includes a catalytic distillation column  520 , olefin feed system  422 , azeotropic mixture feed system  424 , a liquid product recovery system  426 , and a volatiles recovery system  428 . Second liquid product recovery system  502  comprises a take off line  504  for a side stream. Take off line  504  extends from third portion  446  of interior  440  of column  520  at a position adjacent a distillation tray (not illustrated) situated between base  438  and lower catalyst bed  447 . A liquid mixture  506  rich in ethanol  414  can be withdrawn as a side stream in a direction indicated by an arrow  508  from interior  440  through take off line  504 . 
     The present invention confers advantages over the PRIOR ART, as will now be shown through the example of production and recovery of isopropanol. Hydration of propene to isopropanol using existing technology is accomplished by one of several different processes, as described above. In each conventional process, the isopropanol produced in the reactor is one component in a mixture with water and other products. Water is removed from the isopropanol product mixture using countercurrent or extractive methods. The isopropanol must then be recovered from the fluid of the countercurrent stream or from the extraction fluid, frequently requiring several expensive steps. The present invention removes the water by hydration of an olefin to directly form a second alcohol that is a valuable and easily separable product. Referring to  FIG. 5 , an example of the PRIOR ART is a process  300  operated by the Tokyoyama company for the production of isopropanol. Process  300  has a propene feed system  302 , a water feed system  304  and a reactor  306 . The product is an aqueous mixture from which isopropanol is to be recovered. The product mixture from reactor  306  is fed sequentially to a separator  308 , an azeo column  310 , a light end recovery column  312 , a dehydration column  314 , and an isopropanol recovery column  316 , each of which is supported by appropriate valves and pressure and temperature controllers. A comparison of  FIG. 5  with  FIG. 15  shows the greater complexity and consequently the higher capital costs of PRIOR ART process  300  when compared with the present invention. It will be recognized that substituting column  520  of second embodiment of equipment  500  for column  20  of first embodiment of equipment  410  will also confer advantages of the present invention over the PRIOR ART. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Comparison of the present invention with conventional catalytic distillation 
               
               
                 processes. (n/a means data is proprietary or otherwise not available) 
               
            
           
           
               
               
            
               
                   
                 Process: 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Concentration of 
                 40–60 
                 40–60 
                 99 
                 92 
                 95 
                 95 
               
               
                 propene 
               
               
                 in feed stream (wt %): 
               
               
                 Catalyst: 
                 sulfuric acid 
                 sulphuric acid 
                 WO 3 —ZnO/H 3 PO 4   
                 Sulphonic 
                 acidic 
                 strong acid 
               
               
                   
                 (&gt;80%) 
                 (60–80%) 
                 on SiO 2   
                 acid ion- 
                 aqueous 
                 supported 
               
               
                   
                   
                   
                   
                 exchange 
                 solution of 
                 on 
               
               
                   
                   
                   
                   
                 resin 
                 silicotungstate 
                 inorganic 
               
               
                   
                   
                   
                   
                   
                   
                 support 
               
               
                 Catalyst regeneration and 
                 Yes 
                 Yes 
                 n/a 
                 n/a 
                 Yes 
                 No 
               
               
                 recycle needed?: 
               
               
                 Operating pressure (MPa): 
                   1–1.2 
                 2.5 
                 2.5–6.6 
                  8–10 
                 20.3 
                 1.5–4.0 
               
               
                 Operating temperature (° C.): 
                 20–30 
                 60–65 
                 240–260 
                 130–160 
                 270 
                  50–225 
               
               
                 Feed ratio (H 2 O/C 3 H 6 ): 
                 n/a 
                 n/a 
                  1:4–1:10 
                 12:1–15:1 
                 n/a 
                 1:3–1:5 
               
               
                 Conversion of propene (%): 
                 &gt;93 
                 &gt;93 
                 5–6 
                 &gt;75 
                 60–70 
                 20–33 
               
               
                 Selectivity to isopropanol (%): 
                 98 
                 98 
                 96 
                 93 
                 98–99 
                 &gt;99.8 
               
               
                   
               
            
           
         
       
     
     The process of the first aspect of the present invention will now be illustrated using the following non-limiting examples. In each EXAMPLE, the process described and the data obtained have been modeled using the commercially available computer program ASPENPLUS, with MESH equations and the UNIFAC method. The results have been confirmed by experiment using at least one of the AMBERLIST series of acidic cation exchanged resins or SILICALITE as catalyst  42  in laboratory scale equipment for first embodiment of equipment  10 , and as both of first catalyst  142  and second catalyst  242  in laboratory scale equipment for second embodiment of equipment  100 . 
     EXAMPLES 
     Examples 1 through 4 will describe the catalytic distillation process of the present invention as applied to the hydration of propene for the production of substantially anhydrous isopropanol, using a range of operating conditions. Example 5 will describe a similar process for the production of substantially anhydrous tertiary butanol by the hydration of isobutene. 
     In each of the Examples the positions within the pertinent catalytic distillation column will be identified as numbered stages. Stage  1  is a distillation stage immediately below top  26 . Further stages are then numbered sequentially in a direction toward base  28 . 
     Example 1  
     Referring to  FIG. 9 , catalytic distillation column  12  having single catalyst bed  40  has been used for hydration of propene to isopropanol at a pressure of 2 megaPascals. The reaction mixture includes propene, water, isopropanol and di-isopropyl ether, also known as DIPE. The computer model was run for catalytic distillation column having the dimensions illustrated in  FIG. 9 . It has been found that catalytic distillation column  12  having the above dimensions is effective for separation of propene at top  26  and liquid isopropanol at base  28 . First portion  32  of interior cavity  30  has four stages for rectification of volatiles. Stage  5  comprises a second portion  34  of interior cavity  30  and contains catalyst bed  40 . Third portion  36  of interior cavity  30  comprises stage  6  through stage  26 , for stripping liquid isopropanol from the reaction mixture. The temperatures at stage  1 , stage  26 , and at catalyst bed  40  at stage  5  respectively are 50° C., 186° C. and 126° C., as illustrated. The molar feed rates for propene and water and the recovery rates for propene and isopropanol are each illustrated as values in kilomoles per hour. Propene conversion is 25% and water conversion is in excess of 99%. The purity of the isopropanol product stream is over 99% under these operating conditions, with the balance being mainly water and a trace of DIPE. 
     Example 2  
     Referring to  FIG. 10 , catalytic distillation column  12  having substantially the same design and size as in Example 1 has been used for hydration of propene to isopropanol at a pressure of 4 megaPascals. The computer model has been used to determine that the temperatures at stage  1 , stage  26 , and at catalyst bed  40  at stage  5  respectively are 85° C., 218° C. and 169.6° C., as illustrated in  FIG. 10 . The molar feed rates for propene and water and the recovery rates for propene and isopropanol are each illustrated as values in kilomoles per hour. Propene conversion is 35%, water conversion is 96.7%, and the purity of the isopropanol stream is over 95%, with 5% DIPE, under these operating conditions. 
     Example 3 
     Referring to  FIG. 11 , catalytic distillation column  112  having two spaced apart catalyst beds  140  and  240  has been used for hydration of propene to isopropanol at a pressure of 2 megaPascals. The computer model was run for catalytic distillation column having the dimensions illustrated in  FIG. 11 . First portion  32  of interior cavity has two stages for rectification of volatiles. Second portion  34  contains first catalyst bed  140  at stage  5  and second catalyst bed  240  at stage  3 , first catalyst bed  140  and second catalyst bed  240  being spaced apart by stage  4 . Third portion  36  comprises stage  6  through stage  26 , for stripping liquid isopropanol from the reaction mixture. The temperatures at stage  1 , stage  28 , at first catalyst bed at stage  5  and at second catalyst bed at stage  3  respectively are 50° C., 187° C., 137° C. and 132° C., as illustrated. The molar feed rates for propene and water and the recovery rates for propene and isopropanol are each illustrated as values in kilomoles per hour. Propene conversion is 35% and water conversion is in excess of 99%. The purity of the isopropanol stream is over 99% under these operating conditions, with the balance being mainly water and a trace of DIPE. 
     The profile of the reaction mixture by stages is illustrated in  FIG. 6  for use of catalytic distillation column  112 , and condenser  73  and reboiler  83 , as illustrated in  FIG. 3 . The effluent stream fed to reboiler  83  and to first volatiles line  80  comprises only unreacted propene, the mole fraction of which is shown as plot line  90  in  FIG. 6 , and propane, shown as plot line  92 , a contaminant in propene feed  44 . Liquid product  66  collected via first product line  72  comprises over 99% isopropanol, shown as plot line  94 , containing a very small amount of water, shown as plot line  96 , and DIPE, shown as plot line  98 . At stage  12  through stage  26  of the liquid product stripping zone at third portion  36  of interior cavity  30 , substantially all water is volatilized as a volatile two-component azeotropic mixture with isopropanol. At stage  6  through stage  12  a volatile three-component mixture of water, DIPE and isopropanol is returned to the vicinity of reaction zone at second portion  34 . In the rectification zone at first portion  32 , substantially all isopropanol, water and DIPE are returned as heavier components from stage  1  and stage  2  into the reaction zone at second portion  34 . 
     Example 4 
     Referring to  FIG. 12 , catalytic distillation column  112  having substantially the same design and size as in Example 3 has been used for hydration of propene to isopropanol at a pressure of 4 megaPascals. The computer model has been used to determine that the temperatures at stage  1 , stage  28 , at first catalyst bed at stage  5  and at second catalyst bed at stage  3  are respectively 92° C., 211° C., 159° C. and 157° C., as illustrated. The molar feed rates for propene and water and the recovery rates for propene and isopropanol are each illustrated as values in kilomoles per hour. Propene conversion is 36% and water conversion is in excess of 99%. The purity of the isopropanol stream is over 99% under these operating conditions, with the balance being mainly water and a trace of DIPE. 
     The profile of the reaction mixture by stages is illustrated in  FIG. 7  for use of catalytic distillation column  112 , and condenser  73  and reboiler  83 , as illustrated in  FIG. 3 . The effluent stream fed to reboiler  83  and to first volatiles line  80  comprises only unreacted propene, the mole fraction of which is shown as plot line  90  in  FIG. 7 , and propane, shown as plot line  92 , a contaminant in propene feed  44 . Liquid product  66  collected via first product line  72  comprises over 99% isopropanol, shown as plot line  94 , containing a very small amount of water, shown as plot line  96 , and DIPE, shown as plot line  98 . At stage  21  through stage  26  of the liquid product stripping zone at third portion  36  of interior cavity  30 , substantially all water is volatilized as a volatile three-component azeotropic mixture with isopropanol and DIPE. At stage  6  through stage  21  the volatile three-component mixture of water, DIPE and isopropanol is returned to the vicinity of reaction zone at second portion  34 , stage  3  through stage  5 . In the rectification zone at first portion  32 , substantially all isopropanol, water and DIPE are returned as heavier components from stage  1  and stage  2  into the reaction zone at second portion  34 , stage  3  through stage  5 . 
     It can be seen from  FIGS. 6 and 7  that the process of the present invention affords advantages for manufacture of isopropanol when compared with conventional processes exemplified by the process illustrated in  FIG. 5 . The advantages include production of substantially anhydrous isopropanol as liquid product, and less complex equipment and hence less costly capital and operation costs for the process. 
     It can be seen by comparison of  FIG. 6  with  FIG. 7  that operation of the process of the present invention for production of isopropanol at a pressure about 2 megaPascals is even more advantageous than operation of said process at a pressure about 4 megaPascals. The liquid product produced at the operating pressure about 2 megaPascals, illustrated in  FIG. 6 , is more anhydrous and contains considerably less DIPE as a contaminant than the corresponding product produced at the operating pressure about 4 megaPascals, illustrated in  FIG. 7 . 
     It can be seen by comparison of Example 3 with Example 1 and by comparison of Example 4 with Example 2 that operation of the process of the present invention for production of isopropanol using catalytic distillation column  112  having two spaced apart catalyst beds  140  and  240  has advantages over operation of said process using catalytic distillation column  12  having single catalyst bed  40 . The advantages include using a lower molar ratio of propene to water, thereby having the beneficial effect of reducing the cost of purifying and recycling unreacted propene by reducing the amount of unreacted propene recovered from stage  1 . 
     Example 5 
     Referring to  FIG. 13 , catalytic distillation column  112  having substantially the same design and size as in Example 3 has been used for hydration of isobutene to tertiary butanol at a pressure of 1.2 megaPascals. The computer model has been used to determine that the temperatures at stage  1 , stage  26 , at first catalyst bed at stage  5  and at second catalyst bed at stage  2  are respectively 80° C., 168° C., 85.8° C. and 81.6° C., as illustrated. The molar feed rates for isobutene and water and the recovery rates for isobutene and tertiary butyl ether are each illustrated as values in kilomoles per hour. Isobutene conversion is 33.6%, water conversion is in excess of 99%, and the purity of the tertiary butanol stream is over 99.9% under these operating conditions. 
     The profile of the reaction mixture by stages is illustrated in  FIG. 8  for use of catalytic distillation column  112 , and condenser  73  and reboiler  83 , as illustrated in  FIG. 3 . The effluent stream fed to reboiler  83  and to first volatiles line  80  comprises only unreacted isobutene, the mole fraction of which is shown as plot line  190  in  FIG. 8 . It will be recognized that isobutane and other contaminants may be present in the isobutene feed. In the present Example the feed is pure isobutene, and said contaminants are not included. Liquid product  66  collected via first product line  72  comprises over 99% tertiary butanol, shown as plot line  194 , containing a very small amount of water, shown as plot line  96 . It has been found that tertiary butanol is substantially free of di-tertiary ether as a by-product when isobutene is catalytically hydrated using an acidic cation exchange resin as catalyst in a batch process (Odioso et al.,  Industrial and Engineering Chemistry , March 1961, Volume 53 (3), pages 209–211). Similarly, it has been shown that hydration of linear butenes to 2-butanol over an acidic cation exchange resin as catalyst produces no measurable amounts of di-secondary butyl ether as a by-product. Consequently, production of di-tertiary butyl ether as a by-product has been excluded from the model of the present Example. At stage  6  through stage  26  of the liquid product stripping zone at third portion  36  of interior cavity  30 , substantially all water is volatilized as a volatile two-component azeotropic mixture with tertiary butanol and is returned to the vicinity of reaction zone at second portion  34 , at stage  2  through stage  5 . In the rectification zone at first portion  32 , at stage  1 , substantially all tertiary butanol and water are returned as heavier components from stage  1  into the reaction zone at second portion  34 , stage  2  through stage  5 . 
     It can be seen from  FIG. 8  that the process of the present invention affords advantages for manufacture of tertiary butanol when compared with conventional processes, including production of substantially anhydrous tertiary butanol as liquid product, and less complex equipment and hence less costly capital and operation costs for the process. 
     The process of the second aspect of present invention will now be illustrated using the following non-limiting Examples. In the Examples, the process described and the data obtained have been modeled using the commercially available computer program ASPENPLUS, with MESH equations and the UNIFAC method. The results have been confirmed by experiment using the AMBERLIST series of acidic cation exchanged resins or SILICALITE as catalyst  50  in laboratory scale equipment. 
     In the Examples the positions within catalytic distillation column  20  are identified as numbered stages: stage  1  is a distillation stage immediately below top  36 . Further stages are then numbered sequentially to a last stage adjacent base  38 . 
     Example 6 
     Referring to  FIGS. 14 ,  15  and  17 , catalytic distillation column  420  having two spaced apart catalyst beds  447 ,  448  has been used for recovery of ethanol by reaction of 2-methyl-2-butene with the water content of a near azeotropic mixture  12  comprising 90% ethanol and 10% water at a pressure of 0.5 megaPascals. The computer model was run for catalytic distillation column  420  having the dimensions illustrated in  FIG. 17 . First portion  442  of interior cavity has one stage for rectification of volatiles. Second portion  444  contains lower catalyst bed  447  at stage  7  and upper catalyst bed  448  at stage  2 , lower catalyst bed  447  and upper catalyst bed  448  being spaced apart by stage  3  through stage  6 . Third portion  446  comprises stage  8  through stage  34 , for stripping a liquid mixture of ethanol and 2-methyl-2-butanol from the reaction mixture. The temperatures at stage  1 , stage  34 , at lower catalyst bed  447  at stage  7  and at upper catalyst bed  448  at stage  2  respectively are 86° C., 126° C., 102° C. and 93° C., as illustrated. The pressure used is 0.5 Mpa, and the distillate rate is 45.5 kmol/h The molar feed rates for 2-methyl-2-butene and azeotropic mixture  412 , and the recovery rates for ethanol, 2-methyl-2-butanol and unreacted 2-methyl-2-butene are each illustrated as values in kilomoles per hour. 2-Methyl-2-butene conversion is 4.5% and water conversion is over 12%. The alcohol content of liquid product  52  is over 99.9% under these operating conditions, with the balance being water (0.04%). 
     The profile of the reaction mixture by stages is illustrated in  FIG. 16  for use of catalytic distillation column  412 , and condenser  490  and reboiler  474 , as illustrated in  FIG. 15 . The effluent stream fed to condenser  490  and to first volatiles line  486  comprises mainly unreacted 2-methyl-2-butene, the mole fraction of which is shown as plot line  4120  in  FIG. 16 , unreacted water, shown as plot line  4122 , and ethanol, shown as plot line  4124 . Liquid product  452  collected via first product line  472  comprises over 99% alcohols: ethanol shown as plot line  4124  and 2-methyl-2-butanol shown as plot line  4126 , containing a very small amount of water, plot line  4122 . Under the reaction conditions of the present example, all di-(2-methyl-2-butyl) ether, plot line  4128 , formed is in equilibrium with water, 2-methyl-2-butanol and 2-methyl-2-butene, and is retained predominantly within the reaction mixture between stage  2  and stage  18 . At stage  1  through stage  27 , substantially all water is volatilized as a mixture with ethanol and 2-methyl-2-butanol and is returned to the vicinity of reaction zone at second portion  434 , stage  2  through stage  7 . In the rectification zone at first portion  432 , substantially all ethanol, water and 2-methyl-2-butanol are returned as heavier components from stage  1  into the reaction zone at second portion  434 . 
     Ethanol and 2-methyl-2-butanol are readily separated by distillation in column  4108 , as illustrated in  FIG. 14 . 
     Example 7 
     The equipment used in Example 7 is the same as that used in Example 6. The difference is that the operating conditions have been changed, resulting in differences in the composition of the product streams. 
     The feed rate of azeotropic mixture  412  is 90 kmol/h ethanol  414  and 10 kmol/h water  416 . The feed rate of 2-methyl-2-butene  418  is 35 kmol/h. The temperatures at stage  1 , adjacent top  436 , at stage  34 , adjacent base  438 , at upper catalyst bed  448  at stage  2  and at lower catalyst bed  447  at stage  7  are 86° C., 125° C., 93° C. and 99° C., respectively. The pressure used is 0.5 MPa, and the distillate rate is 40.5 kmol/h. When first embodiment of equipment  410  is operated using these conditions and feed rates, the compositions of the product streams are as follows. Liquid  452  recovered at base  438  of column  20  comprises primarily ethanol (83 kmol/h), 2-methyl-2-butanol (1.9 kmol/h), ethyl (2-methyl-2-butyl) ether (3.2 kmol/h), and water (1.06 kmol/h). Volatiles  468  recovered from top  436  of column  420  include primarily 2-methyl-2-butene (29.9 kmol/h), ethanol (3.6 kmol/h), and water (7.0 kmol/h). 
     A comparison of Example 7 with Example 6 shows that operation of the present process under the conditions for Example 7 produces a liquid product  452  that contains a significant amount of ethyl (2-methyl-2-butyl) ether in contrast to the conditions of Example 6. 
     Example 8 
     Referring to  FIG. 18 , catalytic distillation column  520  having a total of 38 stages has been used for recovery of ethanol by reaction of 2-methyl-2-butene with the water content of a near azeotropic mixture  412  comprising 90% ethanol and 10% water at a pressure of 0.5 megaPascals. Catalytic distillation column  520  has two spaced apart catalyst beds  447 ,  448 . Second liquid product recovery system  502  withdraws ethanol-rich liquid from a distillation plate at stage  30 . Upper catalyst bed  448  is at stage  2  and lower catalyst bed  447  is at stage  7 . The operating conditions for Example 8 are otherwise similar to the operating conditions for Example 6. 
     Azeotropic mixture  412  is fed at a rate of 90 kmol/h ethanol and 10 kmol/h water. He feed rate of 2-methyl-2-butene is 35 kmol/h. The temperatures at stage  1 , adjacent top  436 , at stage  34 , adjacent base  438 , upper catalyst bed at stage  2  and at lower catalyst bed at stage  7  are 86° C. 128° C. 93° C., and 104° C., respectively. 
     When second embodiment of equipment  500  is operated under these conditions and flow rates, the liquid product  452  comprises primarily ethanol (5.9 kmol/h) and 2-methyl-2-butanol (1.00 kmol/h). Volatiles  468  comprise primarily 2-methyl-2-butene (33.4 kmol/h), water (8.3 kmol/h), and ethanol (3.7 kmol/h). The liquid mixture  506  withdrawn as a side stream through take off line  504  comprises ethanol (80.3 kmol/h), 2-methyl-2-butanol (0.57 kmol/h) and water (0.10 kmol/h). 
     A comparison of Example 8 with Example 6 shows that inclusion of take off line  504  as second liquid product recovery system  502  allows recovery of liquid mixture  506  having a composition with 99% mole fraction ethanol, and minor amounts of impurities. The water content of liquid mixture  506  can be removed by distillation of an azeotropic mixture of the water with a minor portion of the ethanol. Ethanol can be recovered free from 2-methyl-2-butanol by distillation, with loss of a minor portion of the ethanol as a component of the residue. 
     It can be seen from  FIGS. 16 through 18  that the process of the present invention affords advantages for recovery of ethanol from azeotropic mixtures containing water when compared with conventional processes exemplified by the process illustrated in  FIG. 5 . The advantages include production of substantially anhydrous ethanol, concurrent production of a useful higher molecular weight alcohol as a product, and less complex equipment and hence less costly capital and operation costs for the process. The higher molecular weight alcohol may be recovered as a useful mixture with ethanol, such as a solvent or an automotive fuel additive, or as a separate product stream, as illustrated in the Examples.