Abstract:
A process for reaction and separation which comprises inputting a process material into at least one column of a plurality of columns wherein each column has at least one inlet for accepting flow from another column or group of columns, an external feed stream, an external eluent stream or a combination thereof, and each column has at least one outlet for connecting to another column, a group of columns, an external product stream or a combination thereof. Each column is independently operable in an up-flow or down-flow mode and connected independently to one of the group comprising another column, an external feed stream, an external eluent stream, an external product stream and combinations thereof.

Description:
CROSS REFERENCE  
       [0001]    This application is a continuation-in-part of copending U.S. patent application Ser. No. ______ (Attorney Docket Number 02-254) filed on Jul. 29, 2002. 
     
    
     
       FIELD OF INVENTION  
         [0002]    This invention relates to a process for chemical reaction and separation using a liquid-solid contacting system and, more particularly, to a chemical reaction and separation process using a plurality of columns wherein each column can be independently connected and independently operated for flow inlet and outlet, such as parallel fluid flow, reverse fluid flow or combination of flows.  
         BACKGROUND OF THE INVENTION  
         [0003]    Combining a process for conducting a continuous reaction with concurrent separation into a single process technique has received renewed attention in recent years. Various reaction/separation technologies are being investigated and have reached differing degrees of development or commercial viability. Fairly developed techniques include, for example, reactive distillation techniques and reactive chromatography. Other techniques, such as reactive membranes and reactive crystallization techniques, are also being developed. Some of these techniques have provided certain benefits such as reduced capital costs, higher productivity, higher product yields and improved selectivity when competing reactions are taking place. For instance, reactive distillation, where simultaneous reaction and distillation separation processes are carried out, has been implemented for the production of methyl acetate. This technique resulted in five times lower investment and five times lower energy use than the traditional two-step process where the reaction is carried out as a first step and the distillation separation is carried out as a separate second step. Despite these advantages, however, this technique has drawbacks, which include temperature sensitivity and azeotrope formation.  
           [0004]    Reactive chromatography systems have also been used for conducting combined reaction and separation. Several different reactive chromatography systems have been investigated including a fixed bed with a pressure swing, cylindrical annular bed with a rotating feed input source, a countercurrent moving bed, and a simulated bed. The choice of a particular reaction/separation technology is made based on the specific requirements of specific applications. Each application will have a particular set of requirements in terms of product yield, purity, process productivity, material handling, etc. (See generally, Vaporciyan, G. G.; Kadelec, R. H. AIChE J. 1987, 33 (8), 1334-1343; Fish, B. B.; Carr, R. W. Chem. Eng. Sci. 1989, 44, 1773-1783; and Carr, R. W.; In Preparative and Production Scale Chromatography, Ganetsos, G., Barker, P. E., Eds.; Chromatographic Science Series Vol. 61; Marcel Dekker: New York, 1993; Chapter 18.) Traditionally, the preferred method for carrying out continuous reactive chromatography is the simulated moving bed reactor (SMB) configuration.  
           [0005]    Traditional SMB technology (as shown in FIG. 1) comprises a circulation flow path having multiple beds packed with solid separation/catalyst filler connected in series and allowing a circulation liquid to be forcibly circulated through in one direction. It also has a port for introducing desorbing liquid into the circulation flow path, an extract port for removing circulation liquid carrying the adsorptive constituents (extracts) from the circulation flow path, a feedstock port for introducing feed stock which contains the constituents to be separated, or reacted and separated, into the circulation flow path, and a raffinate port for removing circulation liquid carrying the weakly adsorptive constituents (raffinate) from the circulation flow path.  
           [0006]    As shown in the prior art in FIG. 1, the prior art SMB process is illustrated showing a combined reaction and separation by the general reaction A→B+C. The process is illustrated using four “zones.” Typically, although not always, there are two inlets and two outlets in the SMB system unit. The areas defined between them create the four zones. Component A is feed material  11 , which is fed into the SMB system between Zone II and Zone III. Component A decomposes to form Component B and Component C. Component B is the more strongly adsorbed component and therefore moves with the solid in the direction of the extract outlet, which lies between Zone III and Zone IV. At the extract outlet, Component B is collected as extract product  17 . Component C is the more weakly adsorbed component and moves with the liquid in the direction of the raffinate outlet, which lies between Zone I and Zone II. At the raffinate outlet, Component C is collected as the raffinate  19  product. The eluent  15  is introduced to the system between Zone I and Zone IV to remove the more strongly adsorbed Component B and to act as the liquid carrier for the system. A number of reactions have been reported:  
           [0007]    The SMB process has been demonstrated to significantly increase product yield from equilibrium-limited, liquid phase esterification reactions. Esterification of acetic acid with β-phenethyl alcohol is disclosed in M. Kawase, T. B. Suzuki, K. Inoue, K. Yoshimoto, K. Hashimoto, Chem. Eng. Sci., Vol 51, 2971-2976 (1996). Esterification of acetic acid with ethanol is disclosed in M. Mazzotti, A. Kruglov, B. Neri, D. Gelosa, M. Morbidelli, Chem. Eng. Sci., Vol 51, 1827-1836 (1996); and acetic acid esterification with methanol is disclosed in U.S. Pat. Nos. 5,405,992 and 5,618,972.  
           [0008]    U.S. Pat. No. 5,502,248 shows that the equilibrium-limited, liquid phase ester hydrolysis reaction of methyl acetate can be significantly increased through the use of reactive SMB.  
           [0009]    Ray A., Tonkovich, A. L., Aris, R., Carr, R. W., Chem. Eng. Sci., Vol. 45, No. 8, 2431-2437 (1990) demonstrates that the product yield from the gas phase equilibrium-limited reaction for hydrogenation of mesitylene can be significantly increased using reactive SMB.  
           [0010]    A. V. Kruglov, M. C. Bjorklund, R. W. Carr, Chem. Eng. Sci., Vol 51, 2945-2950 (1996), demonstrates that reactive SMB can be used to increase the product yield with the gas phase reaction for oxidative coupling of methane.  
           [0011]    The feasibility of the condensation of phenol with acetone to form bisphenol-A and water and the simultaneous separation of the products has been predicted through a numerical simulation (Kawase, M.; Inoue, Y.; Araki, K.; Hashimoto, K. Catalyst Today 1999, 48, 199-209).  
           [0012]    Despite these advantages, the traditional SMB techniques have certain drawbacks. The traditional SMB configuration has always been defined as a plurality of beds connected in series and employing a unidirectional fluid flow. This limited configuration inherently prevents the system from handling many reaction/separation applications, such as those that require high mass flow, toxin removal, and individual optimization of reaction and separation conditions. With these applications, the traditional SMB reactor system becomes very complicated, very expensive, and sometimes impractical. Furthermore, none of the present technologies allow for a continuous reaction and separation process using contacting beds arranged in parallel, rather than series, having reverse flow capabilities, or combination unit capabilities. Accordingly, it is an object of the present invention to provide a process for performing combined reaction and separation that further provides parallel fluid flow, reverse flow, or combination unit design, or a combination of any of these thereby eliminating many of the prior art limitations. It is a further object of the invention to provide a process for performing combined reaction/separation step in a single processing unit to greatly decrease processing cost while increasing throughout.  
         SUMMARY OF INVENTION  
         [0013]    Generally, the present invention provides a reactive chromatography process for performing the dual functions of chemical reaction and separation either simultaneously or sequentially using a plurality of beds or columns comprised of a solid or mixture of solids independently connected in a either a series or parallel configuration. Each column has at least one inlet for accepting flow from a connected column, an external stream feed, an external eluent stream or a combination thereof, and at least one outlet for connecting to another column, an external product stream or a combination thereof; each said column being operable in an up-flow or down-flow mode. The up-flow mode can be described by fluid flowing in the direction of the top of the column and the down-flow mode has a fluid flow from the top of the column in a general vertical direction downward. Independently connected can include a column or a group of columns each connected to another column, columns or group of columns or any other sources such as feed, external, event, or external products in any way the process requires without any preset flow pattern. The external product can be raffinate or extract or both. Each column, for example, the flow configuration can be modified to allow for reverse fluid flow. In another example, the beds are arranged to create a combination unit design configuration. In still another example, the process provides for a parallel fluid flow configuration wherein at least one of the beds is connected in parallel.  
           [0014]    The beds preferably contain a solid or mixture of solids that act as a catalyst for the desired reaction and an adsorbent or separation media for removing the reaction product or other desired components. There are a wide variety of solid catalysts and adsorbents available. Such materials include, but are not be limited to, activated carbon, silica gels, aluminas, zeolites, zirconias, titanias, silicates, diatomaceous earths, and ion exchange resins. In one embodiment, a solid is referred where it sufficiently performs both the catalyic and adsorbent function. Where two or more solids are used, one performs the catalyic function while the other perform the separation function. These materials are chosen to provide enhanced reaction and separation over a single material. Also, it is possible that the solid acts only as a separation medium and the catalyst is not part of the solid phase but rather is dissolved in the liquid phase.  
           [0015]    The process of the invention also uses one or more eluents to selectively desorb the reaction products, byproducts, or contaminants from the bed using an isocratic elution or a gradient elution process. The eluent comprises or contains a liquid capable of displacing such reaction product, byproduct, or contaminant from the adsorption bed. Examples of eluents include, for example, alcohols, ketones, esters, aliphatic hydrocarbons, aromatic hydrocarbons, ethers, carboxylic acids, halogenated hydrocarbons, amides, nitrites, water, or buffered solutions. Mixtures of eluents may also be used.  
           [0016]    The feedstock supplied to the present invention may be a single compound or multiple compounds as either a neat material or a solute in solution. It may include a wide variety of materials such as commercial chemicals, fine chemicals, drugs, pharmaceuticals, agrochemicals, foodstuffs, perfumes, flavors, fragrances, odorants, colorants, petrochemicals, etc.  
           [0017]    Examples of some of the types of reactions that can be used with this process are shown in Table 1.  
               TABLE 1                           Esterification:       Methanol + Acetic Acid δ Methyl Acetate + Water       Ethanol + Acetic Acid δ Ethyl Acetate + Water       Butanol + Acetic Acid δ Butyl Acetate + Water                 -Phenethyl Alcohol + Acetic Acid δ          -Phenethyl Acetate + Water       Ester Hydrolysis:       Methyl Acetate + Water δ Methanol + Acetic Acid       Ethyl Acetate + Water δ Ethanol + Acetic Acid       Butyl Acetate + Water δ Butanol + Acetic Acid                 -Phenethyl Acetate + Water δ          -Phenethyl Alcohol + Acetic Acid       Etherification:       t-Butyl Alcohol + Methanol δ Methyl t-Butyl Ether (MTBE) + Water       Isoamylene + Methanol δ t-Amyl Methyl Ether (TAME)       Isomerization:       (ortho, para) Bisphenol-A δ (para, para) Bisphenol-A       Condensations:       Phenol + Acetone δ Bisphenol-A + Water       Methanol + Acetic Acid δ Methyl Acetate + Water       Ethanol + Acetic Acid δ Ethyl Acetate + Water       Butanol + Acetic Acid δ Butyl Acetate + Water                 -Phenethyl Alcohol + Acetic Acid δ          -Phenethyl Acetate + Water       t-Butyl Alcohol + Methanol δ Methyl t-Butyl Ether (MTBE) + Water       Amide Synthesis:       Aniline + Acetic Anhydride δ Acetanilide + Acetic Acid       Dehydration:       t-Butyl Alcohol δ Isobutylene + Water       Oxidation:       Cumene + Oxygen δ Phenol + Acetone                  
 
           [0018]    Preferably, the present invention is used in combination with a continuous liquid-solid contacting device. Continuous liquid-solid contacting devices generally strive to move a liquid phase in counter-current contact with a solid phase through various means. Some systems use multiple columns and a plurality of valves. Others use bed sections stacked in a vertical tower and fed by a rotary valve. A general review of the various devices can be found in U.S. Pat. No. 5,676,826, which is incorporated herein by reference. Although any of the devices can be used with the present invention to achieve the desired continuous reaction and separation, preferred devices include those disclosed in U.S. Pat. Nos. 5,676,826; 4,808,317; 4,764,276; 4,522,726 and U.S. patent application Ser. No. 09/452,256. U.S. patent application Ser. No. 09/452,256 is incorporated herein by reference.  
           [0019]    In a preferred embodiment, the process uses a liquid-solid contacting apparatus having a plurality packed columns of, each of which have a supply conduit and a discharge conduit adapted for connection to a disk having a plurality of ports for connection being associated with supply and discharge conducts at least said columns or said disk being mounted for rotation about an axis so that by rotation said conduits and said ports in the disk are alignable for direct flow communication therebetween between such that, a plurality of supply and discharge conduits to communicate with associated other supply and discharge conduits of the columns, and by synchronizing rotation at least the columns and the disk by the improvement therein comprising flowing a process material through each of said columns to react and separate said flow material.  
           [0020]    Particularly, when used with the present process, this device allows for a wide variety of processing possibilities that have not been taught in the prior art of combined reaction/separation technologies. The ability to incorporate parallel liquid flow, reverse liquid flow, and combination unit configuration, as single or multiple zones and in any combination within a single unit, is a capability that is unique to the present invention. This can prove especially advantageous in the present invention because this process is not limited to a series bed arrangement and unidirectional fluid flow as is the prior art. This flexibility advantageously increases productivity, reduces costs and improves product quality over traditional processes. Other features, aspects and advantages of the present invention will become better understood or apparent from a perusal of the following detailed description and examples of the invention and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a schematic representation of a prior art configuration of a general SMB process.  
         [0022]    [0022]FIG. 2 is a schematic representation of an embodiment of the present invention using a reverse flow configuration.  
         [0023]    [0023]FIG. 3 is a schematic representation of an embodiment of the present invention using a parallel flow configuration.  
         [0024]    [0024]FIG. 4 is a schematic representation of an embodiment of the present invention using a combination unit design.  
         [0025]    [0025]FIG. 5 is a schematic representation of an embodiment of the present invention using another combination unit design. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    The present invention provides a process for chemical reaction and separation using multiple beds comprised of a solid or mixture of solids connected in series, parallel, or combination of such configurations. The reaction/separation can occur concurrently or sequentially. In a preferred arrangement, the beds are configured to have a reverse flow, or a combination unit configuration or a parallel flow configuration or any combination thereof. Preferably, the invention is used in combination with a continuous liquid-solid contacting device. The present invention can be used with a variety of different types of reactions. Examples of some of the types of reactions that can be used with this process are shown above in Table 1. The examples below further show the various configurations of the process. Each may be used alone or in combination with any of the others.  
       EXAMPLE 1  
     Reverse Flow Configuration  
       [0027]    In an embodiment of the present invention, a unit is designed to operate with a liquid flow direction and a solid flow direction as depicted in FIG. 2. FIG. 2 depicts one possible reverse flow configuration where columns  20  and  21  operate in an up-flow mode whereas the other columns in the unit operate in the down-flow mode. This is just one example of the use of reverse flow.  
         [0028]    The reverse flow configuration provides a variety of uses. For instance, it can be used to remove very strongly adsorbed components. FIG. 2 illustrates the use of the reverse flow configuration. It includes one weakly adsorbed component and two strongly adsorbed components (one of which is more strongly adsorbed). The weakly adsorbed component moves with the liquid in the direction of the raffinate  19  outlet and is removed as the raffinate product. The two strongly adsorbed components move with the solids in the direction of the extract outlets  17 , 18 . The less strongly adsorbed component of the two moves with the solid in the direction of the extract I outlet  17  where it is eluted from the system by eluent I  15  and becomes the extract I product  17 . The more strongly adsorbed component of the two continues to move past the extract I outlet  17  in the direction of the extract II outlet  18 . This component is eluted by eluent II  16  and becomes the extract II outlet  18 . These components may include a product, byproduct, inhibitor, contaminant, etc. An esterification reaction illustrates one of the advantages of the reverse flow configuration:  
         [0029]    Alcohol+Carboxylic Acid τ Ester+Water  
         [0030]    In this example, alcohol and carboxylic acid act as feed  11  which is introduced into the top of the column. The water is a strongly adsorbed product that is generated by the chemical reaction and moves with the solid in the direction of an extract I outlet  17 . At outlet  17 , the water is extracted by eluent  15  as extract I product. A more weakly adsorbed product which is also generated by the chemical reaction, the ester, moves with the liquid in the direction of raffinate outlet  19  and collected from the system as raffinate product. In this case the alcohol could also be used as the eluent  15 , which will remove the water from the solid phase as extract at outlet  17  and also act as a liquid carrier for the rest of the system.  
         [0031]    The very strongly adsorbed component will accumulate at the top of the column(s). Then, eluent I  15  or a different eluent, eluent II  16 , is directed into the system in the reverse flow configuration to elute this very strongly adsorbed component out of the top of column  21 . Elution of extract at outlet  18  from the top of the column eliminates the need for the eluent to carry the very strongly adsorbed component all the way through the series of columns to effectuate its removal, as is required in the traditional SMB process. Instead, the reverse flow configuration decreases the length of time for the elution or amount of eluent necessary to complete the process thereby resulting in decreased cost and improved productivity and efficiency of the elution step. Further, this reverse flow configuration can also accommodate two different eluents for desorption of the two different strongly adsorbed components.  
         [0032]    The use of the reverse flow configuration is not limited to the previous specific example. Those skilled in the art would realize that, with the present invention, the unique reverse flow configuration can advantageously be incorporated anywhere within the process: elution zone, reaction zone, separation zone, and the like. Because traditional SMB is carried out with unidirectional flow, the present technique is outside of the realm of traditional SMB.  
         [0033]    The ability to incorporate reverse flow configuration into a process will provide the user with certain advantages. The reverse flow configuration can also be used to remove solids that would accumulate on the top of the column(s), therefore allowing the use of a process stream which contains a certain amount of solids or a process stream which has the potential to form solids in the course of the reaction/separation process. In this way solids can be removed continuously from the top of the column, thereby overcoming a disadvantage of the traditional SMB system which is limited to a unidirectional liquid flow. The SMB process does not allow for continuous removal of solids. The solids would either be trapped in the unit or plug the liquid flow all together.  
         [0034]    The use of the present invention is not restricted to the specific configuration shown in FIG. 2. Those skilled in the art will realize that many different variations are possible because of the flexibility and versatility of the present invention.  
       EXAMPLE 2  
     Parallel Flow Configuration  
       [0035]    In another embodiment of the present invention, multiple columns are connected together in parallel flow mode. As shown for example in FIG. 3, the feed  11  column is connected in parallel. The components of the process system can, either alone or alternatively in combination, employ parallel flow, including the feed, eluent, raffinate, or extract streams. This offers the ability to obtain high flow rates while maintaining an acceptable pressure drop and reaction performance for the process. These capabilities prove especially useful for reactions that require long hold-up time and high mass flow. Such reactions can encounter high pressure drops when performed using the prior art configuration where the columns are connected in a series configuration. The pressure drop requirement for a given process is a very important design parameter. As the pressure drop requirement increases, the cost of the equipment increases and at some point the process become impractical or even impossible. The present parallel flow process reduces the cost of the equipment and increases its productivity. In processes where a reduction in pressure drop is not required, the parallel flow configuration allows for higher productivity at a given pressure drop.  
       EXAMPLE 3  
     2-In-1 Configuration (Type A)  
       [0036]    In another embodiment of the present invention, one or multiple columns are connected together separately inside of a separation train, as shown for example in FIG. 4. This combination unit configuration is also referred to herein as a “2-in-1 flow configuration.” The 2-in-1 flow configuration optimizes the reaction and separation operations by allowing each to be carried out under different conditions. In addition to reaction/separation, another reaction may be conducted, i.e., reaction/separation/reaction or 3-in-1. This configuration is not limited to 2-in-1 or 3-in-1, but may be used to perform multiple reactions and separations in N-in-1 configuration, where N is an integer greater than 1. The feed  11  column is not connected directly in series with the column that precedes it, but rather is connected independently into the liquid flow of the system. Thus, the user can vary the hold-up time, the composition, and the temperature for the reaction in the feed II column without limiting the conditions that can be applied to the rest of the process.  
         [0037]    This 2-in-1 flow configuration further combines a fixed bed type reactor and SMB type separation reactor into a single unit to provide the reaction zone in the middle of the process. In this arrangement, feed II column acts as a fixed bed reactor that feeds a reaction product to an SMB unit for separation and additional reaction as needed. The lines physically connect with a T, as shown for example in FIG. 4. The advantage of feeding the fixed bed reacted product into a separate SMB unit has been realized in prior art, such as in U.S. Pat. No. 5,618,972. The combination improves the effectiveness of the fixed bed reactor while also improving the cost efficiency of the SMB unit. The present invention further improves this process by combining two units into a single unit. It eliminates the costs associated with maintaining two freestanding units that are then physically connected together.  
         [0038]    An esterification reaction is used here to illustrate one of the many uses of the 2-in-1 configuration.  
         [0039]    Alcohol+Carboxylic Acid τ Ester+Water  
         [0040]    The alcohol and carboxylic acid are feed  11 . Water is the more strongly adsorbed product and therefore moves with the solid in the direction of extract outlet  17  where it is eluted as extract  17  product. The ester, raffinate  19  product, is the more weakly adsorbed product and moves with the liquid in the direction of the raffinate  19  outlet. In this case, the alcohol could also be used as the eluent  15 . In this case, because this 2-in-1 configuration provides for a feed column that is not directly connected in series, it allows the user to optimize the process parameters for the reaction zone independently from the process parameters that are required for the separation by being able to adjust the temperature, hold up time, and feed composition. This type of process flexibility where one can carry out reaction and separation in one unit while still being able to separately optimize process conditions for each, is not realized with traditional SMB processes that, by definition, entails columns connected in series, Those skilled in the art will realize that this technique can be advantageously applied to wide variety of reactions, such as esterification, ester hydrolysis, etherification, isomerization, condensations, amide synthesis, peptide synthesis, dehydrations, oxidations just to name a few. It will also be realized that the use of the present invention is not restricted to the specific configuration shown in FIG. 3. Those skilled in the art will realize that many different variations are possible because of the flexibility and versatility of the present invention.  
       EXAMPLE 4  
     2-In-1 Configuration (Type B)  
       [0041]    In another embodiment of the present invention, one or multiple columns are connected together in a zone that is still within the same unit but outside the separation process zone. The 2-in-1 flow configuration (type A) shown in Example 3 incorporates a reaction zone into the middle of a traditional SMB process. The composition of the material in the reaction zone is influenced by the composition of the adjacent column which will move into the reaction zone position. With the 2-in-1 flow configuration (type B), the reaction zone V receives the next column from elution in zone I. Because of this process feature, the reaction zone is a clean column rather than a column that already contains a certain composition of material. This allows for additional process optimization that goes beyond the 2-in-1 (type A) configuration. This type of process is also outside the traditional SMB process which relies on columns that are endlessly connected in series. The prior art of reactive SMB does not teach about the use of this type of configuration as it would not necessarily be advantageous under its limited operating conditions.  
         [0042]    The use of the present invention is not restricted to the specific configuration shown in FIG. 5. Those skilled in the art will realize that many different variations of 2-in-1 configurations are possible because of the flexibility and versatility of the present invention.  
         [0043]    The previous examples illustrate the versatility of the present invention. Although the illustrations depict one particular example of each configuration, those skilled in the art will realize that a large number of variations are possible within the scope of this invention. Any given configuration may contain more or less zones than shown in FIGS.  2 - 5 . Each zone may contain anywhere from one to zero to multiple columns. The special function zones (reverse flow, parallel flow, etc.) may be used anywhere in the system and are not limited to the location shown in the illustrations. More than one configuration may be used in a unit and multiple functions can be combined in one unit.  
         [0044]    Those skilled in the art, will realize that this level of process flexibility becomes very complicated and very expensive with the traditional SMB technologies. The advantages listed above will result in reduced capital costs, higher productivity, higher yields, and improved selectivity.  
         [0045]    Those skilled in the art will also realize that the present invention can also be used with many different reaction/separation applications. The present invention can be used for, but not limited to, esterification, ester hydrolysis, etherification, isomerizations, condensations, amide synthesis, peptide synthesis, dehydrations, and oxidations just to name a few.  
         [0046]    While the foregoing has been set forth in considerable detail, the examples and methods are presented for elucidation and not limitation. It will be appreciated from the specification that various modifications of the invention and combinations of elements, variations, equivalents, or improvements therein may be made by those skilled in the art, and are still within the scope of the invention as defined in the appended claims.