| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 09.99 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 07.09.99 |
| PATENT TITLE |
Use of sol-gel derived porous microposite of perfluorinated ion-exchange polymer and metal oxide to isomerize terminal olefins |
| PATENT ABSTRACT |
Porous microcomposites have been prepared from perfluorinated ion-exchange polymer and metal oxides such as silica using a sol-gel process. Such microcomposites possess high surface area and exhibit extremely high catalytic activity. Isomerization of terminal olefins is possible with such porous microcomposites. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 23.07.98 |
| PATENT REFERENCES CITED |
Mauritz, K.A. et al., Polym. Mater. Sci. Eng., 58, 1079-1082, 1988. Olah, G. A. et al., Synthesis, 513-531, 1986. Waller, F.J., Catal. Rev.-Sci. Eng., 1-12, 1986. Weaver, J.D. et al., Catalysis Today, 14, 195-210, 1992. Mauritz, K.A. et al., Multiphase Polymers: Blends and Ionomers, American Chemical Society, 401-417, Chapter 16, 1989. Waller, F.J. et al. Chemtech, 438-441 (Jul. 1987). Waller, F.J., In Polymeric Reagents and Catalysts, Ford, W.T. (Ed.), Chap. 3, ACS Symposium Series 308, ACS, Washington, DC (1986). Martin, C.R. et al., Anal. Chem. 54, 1639-1641 (1982). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A process for the isomerization of an olefin, comprising contacting said olefin at isomerization conditions with a catalytic amount of a porous microcomposite, said microcomposite comprising a perfluorinated ion-exchange polymer with pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, silica or a combination thereof, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to about 90 percent, wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm, and wherein the microcomposite optionally further comprises pores having a size in the range of about 75 nm to about 1000 mn. 2. The process of claim 1 wherein the isomerization conditions comprise a temperature of from about 0.degree. C. to about 300.degree. C., a pressure of from about atmospheric to 100 atmospheres, and a weight hourly space velocity of from about 0.1 to 100 hr.sup.-1. 3. The process of claim 2 wherein the isomerization conditions comprise a temperature of from about 25.degree. C. to about 250.degree. C., a pressure of from about atmospheric to 50 atmospheres, and a weight hourly space velocity of from about 0.1 to 10 hr.sup.-1. 4. The process of claim 1 wherein the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups. 5. The process of claim 1 wherein the network is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide and/or iron oxide. 6. The process of claim 4 wherein the network comprises is silica. 7. The process of claim 1 wherein the weight percentage of perfluorinated ion-exchange polymer is from about 5 to about 80. 8. The process of claim 7 wherein the weight percentage of perfluorinated ion-exchange polymer is from about 5 to about 20. 9. The process of claim 1 wherein the size of the pores is about 0.5 nm to about 30 nm. 10. The process of claim 1 wherein said microcomposite further comprises pores having a size in the range of about 75 nm to about 1000 nm. 11. The process of claim 1 wherein the olefin is a C.sub.4 to C.sub.40 terminal olefin. 12. The process of claim 11 wherein the olefin is 1-butene, 1-heptene or 1-dodecene. 13. The process of claim 12 wherein the olefin is 1-butene. 14. The process of claim 12 wherein the weight percentage of perfluorinated ion-exchange polymer is from about 5 to about 80, the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups, and the network is silica. 15. The process of claims 12 wherein the perfluorinated ion-exchange polymer is prepared from resin having an equivalent weight of about 1070 comprising about 6.3 tetrafluoroethylene molecules for every perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule, and the weight percent of perfluorinated ion-exchange polymer in the microcomposite is about 13%. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION This invention relates to porous microcomposites comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups and/or pendant carboxylic acid groups entrapped within and highly dispersed throughout a metal oxide network, prepared using a sol-gel process. Due to their high surface area and acid functionality these microcomposites possess wide utility as improved solid acid catalysts. TECHNICAL BACKGROUND U.S. Pat. No. 5,252,654 discloses polymeric composites comprising an interpenetrating network of an organic polymer and an inorganic glassy polymer and a process for making such composites. The disclosed material is nonporous, and the use of perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups or pendant carboxylic acid groups is not disclosed. K. A. Mauritz et al., Polym. Mater. Sci. Eng. 58, 1079-1082(1988), in an article titled "Nafion-based Microcomposites: Silicon Oxide-filled Membranes", discuss the formation of micro composite membranes by the growth of silicon oxide microclusters or continuous silicon oxide interpenetrating networks in pre-swollen "NAFION.RTM." sulfonic acid films. "NAFION.RTM." is a registered trademark of E. I. du Pont de Nemours and Company. U.S. Pat. No. 5,094,995 discloses catalysts comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups supported on an inert carrier having a hydrophobic surface comprising calcined shot coke. U.S. Pat. No. 4,038,213 discloses the preparation of catalysts comprising perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups on a variety of supports. The catalytic utility of perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid groups, supported and unsupported has been broadly reviewed: G. A. Olah et al., Synthesis, 513-531(1986) and F. J. Waller, Catal. Rev.-Sci. Eng., 1-12(1986). SUMMARY OF THE INVENTION This invention provides a porous microcomposite comprising perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, preferably from about 5 to about 80 percent, and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm. In a separate embodiment, the microcomposite can simultaneously contain larger pores ranging from about 75 nm to about 1000 nm, wherein these larger pores are formed by introducing acid-extractable filler particles during the formation process. This invention further provides the process of preparation of a porous microcomposite which comprises perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm; said process comprising the steps of: a. mixing the perfluorinated ion-exchange polymer with one or more metal oxide precursors in a common solvent; b. initiating gelation; c. allowing sufficient time for gelation and aging of the mixture; and d. removing the solvent. In a further preferred embodiment the process further comprises at step (a), adding to the mixture an amount from about 1 to 80 weight percent of an acid extractable filler particle, after d; e. acidifying the product of step d by the addition of acid; and f. removing the excess acid from the microcomposite; to yield a microcomposite further containing pores in the range of about 75 nm to about 1000 nm. The present invention also provides an improved process for the nitration of an aromatic compound wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above. The present invention further provides an improved process for the esterification of a carboxylic acid with an olefin wherein the improvement comprises contacting said carboxylic acid with a catalytic microcomposite of the present invention, described above. The present invention also provides an improved process for the polymerization of tetrahydrofuran wherein the improvement comprises contacting said tetrahydrofuran with a catalytic microcomposite of the present invention, described above. The present invention further provides an improved process for the alkylation of an aromatic compound with an olefin wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above. The present invention provides an improved process for the acylation of an aromatic compound with an acyl halide wherein the improvement comprises contacting said aromatic compound with a catalytic microcomposite of the present invention, described above. The present invention further provides an improved process for the dimerization of an alpha substituted styrene, wherein the improvement comprises contacting said alpha substituted styrene with a catalytic microcomposite of the present invention, described above. The present invention further provides a process for regenerating a catalyst comprising a microcomposite of the present invention, as described above, comprising the steps of: mixing the microcomposite with an acid, and removing the excess acid. The present invention also provides a process for the isomerization of an olefin comprising contacting said olefin at isomerization conditions with a catalytic amount of a porous microcomposite, said microcomposite comprising perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, preferably from about 5 to about 80 percent, most preferably from about 5 to about 20 percent and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing data from Example 58 and Table 4b which shows the effect of contact time at 50.degree. C. and He/1-butene=1.2/1.0 on 1-butene isomerization over a 13 wt % "NAFION.RTM." PFIEP/silica microcomposite prepared as in Example 16. DETAILED DESCRIPTION OF THE INVENTION The organic-inorganic polymer microcomposites of the present invention are high surface area, porous microcompositions which exhibit excellent catalytic activity. Whereas the surface area of "NAFION.RTM." NR 50 PFIEP, a commercial product, is approximately 0.02 m.sup.2 per gram, a preferred embodiment of the present invention comprises microcomposites of PFIEP and silica having a surface area typically of 5 to 500 m.sup.2 per gram. The composition of the present invention exists as a particulate solid which is porous and glass-like in nature, typically 0.1-4 mm in size and structurally hard, similar to dried silica gels. The perfluorinated ion exchange polymer (PFIEP) is highly dispersed within and throughout the silica network of the microcomposite of the present invention, and the microstructure is very porous. The porous nature of this material is evident from the high surface areas measured for these glass-like pieces, having typical pore diameters in the range of 1-25 nm. Another preferred embodiment is the use of the present invention in pulverized form. In another preferred embodiment, macroporosity (pore sizes about 75 to about 1000 nm) is also introduced into the microcomposite, resulting in a microcomposite having both increased surface area from the micropores and mesopores (0.5-75 nm) and enhanced accessibility resulting from the macropores (75-1000 nm). Perfluorinated ion-exchange polymers (PFIEP) containing pendant sulfonic acid, carboxylic acid, or sulfonic acid and carboxylic acid groups used in the present invention are well known compounds. See, for example, Waller et al., Chemtech, July, 1987, pp. 438-441, and references therein, and U.S. Pat. No. 5,094,995, incorporated herein by reference. Perfluorinated ion-exchange polymers (PFIEP) containing pendant carboxylic acid groups have been described in U.S. Pat. No. 3,506,635, which is also incorporated by reference herein. Polymers discussed by J. D. Weaver et al., in Catalysis Today, 14 (1992) 195-210, are also useful in the present invention. Polymers that are suitable for use in the present invention have structures that include a substantially fluorinated carbon chain that may have attached to it side chains that are substantially fluorinated. In addition, these polymers contain sulfonic acid groups or derivatives of sulfonic acid groups, carboxylic acid groups or derivatives of carboxylic acid groups and/or mixtures of these groups. For example, copolymers of a first fluorinated vinyl monomer and a second fluorinated vinyl monomer having a pendant cation exchange group or a pendant cation exchange group precursor can be used, e.g., sulfonyl fluoride groups (SO.sub.2 F) which can be subsequently hydrolyzed to sulfonic acid groups. Possible first monomers include tetrafluoroethylene (TFE), hexafluoropropylene, vinyl fluoride, vinylidine fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether), and mixtures thereof. Possible second monomers include a variety of fluorinated vinyl ethers with pendant cation exchange groups or precursor groups. Preferably, the polymer contains a sufficient number of acid groups to give an equivalent weight of from about 500 to 20,000, and most preferably from 800 to 2000. Representative of the perfluorinated polymers for use in the present invention are "NAFION.RTM." PFIEP (a family of polymers for use in the manufacture of industrial chemicals, commercially available from E. I. du Pont de Nemours and Company), and polymers, or derivatives of polymers, disclosed in U.S. Pat. Nos. 3,282,875; 4,329,435; 4,330,654; 4,358,545; 4,417,969; 4,610,762; 4,433,082; and 5,094,995. More preferably the polymer comprises a perfluorocarbon backbone and a pendant group represented by the formula --OCF.sub.2 CF(CF.sub.3)OCF.sub.2 CF.sub.2 SO.sub.3 X, wherein X is H, an alkali metal or NH.sub.4. Polymers of this type are disclosed in U.S. Pat. No. 3,282,875. Typically, suitable perfluorinated polymers are derived from sulfonyl group-containing polymers having a fluorinated hydrocarbon backbone chain to which are attached the functional groups or pendant side chains which in turn carry the functional groups. Fluorocarbosulfonic acid catalysts polymers useful in preparing the microcomposites of the present invention have been made by Dow Chemical and are described in Catalysis Today, 14 (1992) 195-210. Other perfluorinated polymer sulfonic acid catalysts are described in Synthesis, G. I. Olah, P. S. Iyer, G. K. Surya Prakash, 513-531 (1986). There are also several additional classes of polymer catalysts associated with metal cation ion-exchange polymers and useful in preparing the microcomposite of the present invention. These comprise 1) a partially cation-exchanged polymer, 2) a completely cation-exchanged polymer, and 3) a cation-exchanged polymer where the metal cation is coordinated to another ligand (see U.S. Pat. No. 4,414,409, and Waller, F. J. In Polymeric Reagents and Catalysts; Ford, W. T., Ed.,; ACS Symposium Series 308; American Chemical Society; Washington, D.C., 1986, Chapter 3). Preferred PFIEP suitable for use in the present invention comprise those containing sulfonic acid groups. Most preferred is a sulfonated "NAFION.RTM." PFIEP. Perfluorinated ion-exchange polymers are used within the context of the invention in solution form. It is possible to dissolve the polymer by heating it with an aqueous alcohol to about 240.degree. C. or higher for several hours in a high pressure autoclave (see U.S. Pat. No. 4,433,082 or Martin et al., Anal. Chem., Vol. 54, pp 1639-1641 (1982). Other solvents and mixtures may also be effective in dissolving the polymer. Ordinarily, for each part by weight of polymer employed to be dissolved, from as little as about 4 or 5 parts by weight up to about 100 parts by weight, preferably 20-50 parts by weight, of the solvent mixture are employed. In the preparation of the dissolved polymer, there is an interaction between the equivalent weight of the polymer employed, the temperature of the process, and the amount and nature of the solvent mixture employed. For higher equivalent weight polymers, the temperature employed is ordinarily higher and the amount of liquid mixture employed is usually greater. The resulting mixture can be used directly and may be filtered through fine filters (e.g., 4-5.5 micrometers) to obtain clear, though perhaps slightly colored, solutions. The mixtures obtained by this process can be further modified by removing a portion of the water, alcohols and volatile organic by-products by distillation. Commercially available solutions of perfluorinated ion-exchange polymers can also be used in the preparation of the microcomposite of the present invention (e.g., at 5 wt % solution of a perfluorinated ion-exchange powder in a mixture of lower aliphatic alcohols and water, Cat. No. 27,470-4, Aldrich Chemical Company, Inc., 940 West Saint Paul Avenue, Milwaukee, Wis. 53233). "Metal oxide" signifies metallic or semimetallic oxide compounds, including, for example, alumina, silica, titania, germania, zirconia, alumino-silicates, zirconyl-silicates, chromic oxides, germanium oxides, copper oxides, molybdenum oxides, tantalum oxides, zinc oxides, yttrium oxides, vanadium oxides, and iron oxides. Silica is most preferred. The term "metal oxide precursor" refers to the form of the metal oxide which is originally added in the sol-gel process to finally yield a metal oxide in the final microcomposite. In the case of silica, for example, it is well known that a range of silicon alkoxides can be hydrolyzed and condensed to form a silica network. Such precursors as tetramethoxysilane (tetramethyl orthosilicate), tetraethoxysilane (tetraethyl orthosilicate), tetrapropoxysilane, tetrabutoxysilane, and any compounds under the class of metal alkoxides which in the case of silicon is represented by Si(OR).sub.4, where R includes methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl or where R is a range of organic groups, such as alkyl. Also included as a precursor form is silicon tetrachloride. Further precursor forms comprise organically modified silica, for example, CH.sub.3 Si(OCH.sub.3).sub.3, PhSi(OCH.sub.3).sub.3, and (CH.sub.3).sub.2 Si(OCH.sub.3).sub.2. Other network formers include metal silicates, for example, potassium silicate, sodium silicate, lithium silicate. K, Na or Li ions can be removed using a DOWEX.RTM. cation exchange resin (sold by Dow Chemical, Midland, Mich., which generates polysilicic acid which gels at slightly acid to basic pH. The use of "LUDOX.RTM." colloidal silica (E. I. du Pont de Nemours and Company, Wilmington, Del.) and fumed silica ("CAB-O-SIL.RTM." sold by Cabot Corporation of Boston, Mass.) which can be gelled by altering pH and adjusting the concentration in solution will also yield a metal oxide network in the microcomposite of the invention. For example, typical precursor forms of silica are Si(OCH.sub.3).sub.4, Si(OC.sub.2 H.sub.5).sub.4 and Na.sub.2 SiO.sub.3 ; and a typical precursor form of alumina is aluminum tri-secbutoxide Al(OC.sub.4 H.sub.9).sub.3. "Acid extractable filler particles" which are used in the process of the invention to introduce macropores of about 75 to about 1000 nm into the microcomposite include particles which are insoluble in the preparative gel-forming solvent, but are acid soluble and extractable from the formed microcomposite. Such filler particles include, for example, alkali metal carbonates or alkaline earth carbonates, such as calcium carbonate, sodium carbonate and potassium carbonate. The first stage of the process for the preparation of the microcomposite of the present invention involves preparing a gel solution that contains both the perfluorinated ion-exchange polymer (PFIEP) containing pendant sulfonic acid groups and/or pendant carboxylic acid groups and one or more metal oxide precursors in a common solvent. This solvent normally comprises water and various lower aliphatic alcohols such as methanol, 1-propanol, 2-propanol, mixed ethers and n-butanol. Thus, in some cases the water necessary for gel formation can be supplied by the water in the reaction solvent. Other polar solvents which may be suitable for the particular metal oxide precursor/polymer selected include acetonitrile, dimethyl formamide, dimethylsulfoxide, nitromethane, tetrahydrofuran and acetone. Toluene, alkanes and fluorocarbon-containing solvents can also be useful in some instances to solubilize the polymer. Gelation may in some instances self-initiate, for example, when water is present in the common solvent, or via rapid drying, such as spray drying. In other instances, gelation must be initiated, which can be achieved in a number of ways depending on the initial mixture of polymer, metal oxide precursor and solvent selected. Gelation is dependent on a number of factors such as the amount of water present, because water is required for the hydrolysis and condensation reaction. Other factors include temperature, solvent type, concentrations, pH, pressure and the nature of the acid or base used. The pH can be achieved in a number of ways, for example, by adding base to the PFIEP solution or by adding the PFIEP solution to the base, or by adding the metal oxide to the solution than adjusting pH with acid or base. Another variable in addition to the mode of addition for achievement of pH is the concentration of base employed. Gels can also be formed by acid catalyzed gellation. See "Sol-Gel Science", Brinker, C. J. and Scherer, G. W., Academic Press, 1990. Non-gelled PFIEP/metal oxide solution may be spray dried to yield dried PFIEP/metal oxide composites. Time required for the gel forming reaction can vary widely depending on factors such as acidity, temperature, and concentration. It can vary from practically instantaneous to several days. The gel forming reaction can be carried out at virtually any temperature at which the solvent is in liquid form. The reaction is typically carried out at room temperature. Pressure over the gel forming reaction is not critical and may vary widely. Typically the reaction is carried out at atmospheric pressure. The gel forming reaction can be carried out over a wide range of acidity and basicity depending upon the amount of base added to the gel precursor. After formation, but before isolation, the gel, still in the presence of its reaction solvent, may be allowed to stand for a period of time. This is referred to as aging. The product is dried at room temperature or at elevated temperatures in an oven for a time sufficient to remove solvent. Drying can be done under vacuum, or in air or using an inert gas such as nitrogen. Optionally, after aging and/or removal of the solvent, the hard glass-like product can be ground and passed through a screen, preferably a 10-mesh screen. Grinding generates smaller particles (and greater surface area) which are more readily re-acidified. Grinding is especially useful for microcomposites having a high weight percent of PFIEP. Preferably, following removal of the solvent and optional grinding, the material is reacidified, washed and filtered. This may be repeated a number of times. Reacidification of the material converts, for example, the sodium salt of the perfluorosulfonic acid into the acidic, active form. Suitable acids comprise HCl, H.sub.2 SO.sub.4 and nitric acid. A number of reaction variables, for example acidity, basicity, temperature, aging, method of drying and drying time of gels, have been found to affect the pore size and pore size distribution. Both higher pH and longer aging of gels (before solvent removal) lead to larger final pore size in the dried PFIEP/metal oxide gels. Pore size can be varied over a wide range (about 0.5 to about 75 nm) depending on the variables described above. Aging of the wet gels (in the presence of the solvent) for a few hours at 75.degree. C. also leads to an increase in pore size although over a smaller range. This effect is characteristic of silica type gels, where the aging effect gives rise to an increasingly cross linked network which upon drying is more resistant to shrinkage and thus a higher pore size results. See, for example, the text "Sol-Gel" Science, Brinker, C. J. and Scherer, G. W., Academic Press, 1990, pp. 518-523. In the present invention, preferred pore size is about about 0.1 nm to about 75 nm, more preferred about 0.5 to about 50 nm, most preferred is about 0.5 to about 30 mn. Microcomposites comprising macropores (about 75 to about 1000 mn) have also been developed hereunder which have both high surface area and micro-, meso- and macroporosity. Such a structure is easily accessible for catalytic and ion exchange purposes. This unique microstructure of the present invention is prepared by adding sub-micron size particles of calcium carbonate to a PFIEP/metal oxide precursor solution prior to the gelation step. Upon acidification of the glass gels, the calcium carbonate dissolves out leaving large (about 500 nm) pores connected throughout the matrix with a sub-structure of about 10 nm micropores. This kind of structure offers a high surface area PFIEP/metal oxide network within the microcomposite which is readily accessible throughout. Macroporosity can be achieved by adding approximately 1 to 80 wt % (based upon gel weight) of acid-extractable filler particles such as calcium carbonate, to the sol-gel process prior to the gelation step. It is believed that the highly porous structure of the microcomposites of the present invention consists of a continuous metal oxide phase which entraps a highly dispersed PFIEP within and throughout a connected network of porous channels. The porous nature of the material can be readily demonstrated, for example, by solvent absorption. The microcomposite can be observed to emit bubbles which are evolved due to the displacement of the air from within the porous network. The distribution of the PFIEP entrapped within and throughout the metal oxide is on a very fine sub-micron scale. The distribution can be investigated using electron microscopy, with energy dispersive X-ray analysis, which provides for the analysis of the elements Si and O (when using silica, for example) and C and F from the PFIEP fluoropolymer. Fractured surfaces within a particle and several different particles for compositions ranging from 10 to 40 wt % "NAFION.RTM." PFIEP were analyzed, and all of the regions investigated showed the presence of both the silica and PFIEP polymer from the edge to the center of the microcomposite particles; thus the microcomposite exhibited an intimate mixture of Si and F. No areas enriched in entirely Si or entirely F were observed, rather a uniform distribution of Si and F was seen. This bicomponent description is believed to be accurate for areas as low 0.1 micrometer in size. The morphology of the microcomposites, as prepared by Example 1, is somewhat particulate in nature, again as observed using scanning electron microscopy. This is typical of silica gel type material prepared using this sol-gel procedure. The primary particle size is on the order of 5-10 nm. This was also confirmed using small angle x-ray scattering experiments on the material, which revealed a domain size in the range of 5-10 nm. The data is consistent with the PFIEP being entrapped within and highly dispersed throughout the silica. The microcomposites of the invention are useful as ion exchange resins, and as catalysts, for example, for alkylating aliphatic or aromatic hydrocarbons, for decomposing organic hydroperoxides, such as cumene hydroperoxide, for sulfonating or nitrating organic compounds, and for oxyalkylating hydroxylic compounds. A serious drawback to the commercial use of previous perfluorocarbon sulfonic acid catalysts has been their high cost and relatively low catalytic activity. The present invention provides the benefits of reduced costs, higher catalytic activity, and in some cases improved reaction selectivity. Other commercially important applications for PFIEP/silica catalysts of the present invention comprise hydrocarbon isomerizations and polymerizations; carbonylation and carboxylation reactions; hydrolysis and condensation reactions, esterifications and etherification; hydrations and oxidations; aromatic acylation, alkylation and nitration; and isomerization and metathesis reactions. The present invention provides an improved process for the nitration of an aromatic compound wherein the improvement comprises contacting the aromatic compound with a microcomposite of the present invention as a catalyst. For example, in the nitration of benzene, a solution comprising benzene and optionally, a desiccant such as MgSO.sub.4, is heated, typically to reflux at atmospheric pressure under an inert atmosphere, and a nitrating agent, for example, HNO.sub.3 is added. The process is conducted under normal nitration conditions which conditions, such as temperature, are dependent upon the reactivity of the aromatic used. When a microcomposite of the present invention is used as a catalyst in the benzene solution, a high rate of conversion and selectivity to nitrobenzene is demonstrated as compared to "NAFION.RTM." PFIEP alone or to the use of no catalyst (see Table I, Example 42). A preferred catalyst for this process is a microcomposite of the present invention wherein the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups and wherein the metal oxide is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide and/or iron oxide. Most preferred is wherein the perfluorinated ion-exchange polymer is a "NAFION.RTM." PFIEP and the metal oxide is silica, the most preferred "NAFION.RTM." PFIEP having approximately 6.3 tetrafluoroethylene (TFE) molecules for every perfluoro perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule (CF.sub.2 .dbd.CF--O--›CF.sub.2 CF(CF.sub.3)!--O--CF.sub.2 CF.sub.2 --SO.sub.2 F (PSEPVE)) and an equivalent weight of approximately 1070. The present invention further provides an improved process for the esterification of a carboxylic acid by reaction with an olefin wherein the improvement comprises contacting said carboxylic acid with a porous microcomposite of the present invention as a catalyst. For example, the esterification of acetic acid with cyclohexene to yield cyclohexylacetate. This esterification is typically carried out in a reactor. The acetic acid and cyclohexene solution typically comprises excess acetic acid to minimize dimerization of the cyclohexene. Generally, the reaction is run under normal esterification conditions which conditions are dependent upon the reactivity of the carboxylic acid and olefin used. Using as catalyst a microcomposite of the present invention results in specific activity almost an order of magnitude higher than that of other catalysts (see Table II, Example 43). A preferred catalyst for this process is a microcomposite of the present invention wherein the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups and wherein the metal oxide is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide and/or iron oxide. Most preferred is wherein the perfluorinated ion-exchange polymer is a "NAFION.RTM." PFIEP and the metal oxide is silica, the most preferred "NAFION.RTM." PFIEP having approximately 6.3 tetrafluoroethylene (TFE) molecules for every perfluoro perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule (CF.sub.2 .dbd.CF--O--›CF.sub.2 CF(CF.sub.3)!--O--CF.sub.2 CF.sub.2 --SO.sub.2 F (PSEPVE)) and has an equivalent weight of approximately 1070. The present invention also provides an improved process for the alkylation of an aromatic compound with an olefin wherein the improvement comprises using the microcomposite of the present invention as a catalyst. For example, in the alkylation of toluene with n-heptene, the toluene and heptene are dried before use and then mixed and heated, for example, to about 100.degree. C. Dried catalyst comprising the porous microcomposite of the present invention is added to the toluene/n-heptene solution and left to react. This improved process is generally conducted under normal alkylation conditions which conditions are dependent upon the reactivity of the aromatic and olefin used. A high rate of conversion is found using a microcomposite of the present invention as compared to using "NAFION.RTM." NR 50 PFIEP as the catalyst. The preferred catalyst for this process is a microcomposite of the present invention wherein the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups and wherein the metal oxide is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide and/or iron oxide. Most preferred is wherein the perfluorinated ion-exchange polymer is a "NAFION.RTM." PFIEP and the metal oxide is silica, the most preferred "NAFION.RTM." PFIEP having approximately 6.3 tetrafluoroethylene (TFE) molecules for every perfluoro perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule (CF.sub.2 .dbd.CF--O--›CF.sub.2 CF(CF.sub.3)!--O--CF.sub.2 CF.sub.2 --SO.sub.2 F (PSEPVE)) and has an equivalent weight of approximately 1070. The present invention also provides an improved process for the polymerization of tetrahydrofuran to polytetrahydrofuran. The product is polytetramethylene ether acetate (PTMEA), the diacetate of polytetrahydrofuran, which can be used in the preparation of "TERATHANE.RTM." polyether glycol (E. I. du Pont de Nemours and Company, Wilmington, Del.). A process for the polymerization of tetrahydrofuran generally comprises contacting tetrahydrofuran with acetic anhydride and acetic acid in solution usually within a pressure reactor equipped with an agitator. The reaction can be conducted at ambient temperature. The improvement herein comprises adding to the solution as a catalyst the porous microcomposite of the present invention. Contact time can range from 1 hr to 24 hrs. The present invention further provides an improved process for the acylation of an aromatic compound with an acyl halide to form an aryl ketone. A process for the acylation of an aromatic compound generally comprises heating the compound with the acyl halide. The improvement herein comprises contacting the aromatic compound with a catalytic porous microcomposite of the present invention. After allowing sufficient time for the reaction to complete, the aryl ketone product is recovered. The present invention also provides an improved process for the dimerization of an alpha substituted styrene. The improvement comprises contacting the styrene with a catalytic porous microcomposite of the present invention. When using alpha methyl styrene, for example, the styrene may be heated in solution and the catalyst added. The product comprises a mixture of unsaturated dimers (2,4-diphenyl-4-methyl-1-pentene and 2,4-diphenyl-4-methyl-2-pentene) and saturated dimers (1,1,3-trimethyl-3-phenylidan and cis and trans-1,3-dimethyl-1,3-diphenylcyclobutane). A preferred catalyst for the polymerization of tetrahydrofuran, for the acylation of an aromatic compound and for the dimerization of an alpha substituted styrene is a microcomposite of the present invention wherein the perfluorinated ion-exchange polymer contains sulfonic acid groups and wherein the metal oxide is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl silicate, chromic oxide and/or iron oxide. Most preferred is wherein the PFIEP is a "NAFION.RTM." PFIEP and the metal oxide is silica, the most preferred "NAFION.RTM." PFIEP having approximately 6.3 tetrafluoroethylene (TFE) molecules for every perfluoro perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule (CF.sub.2 .dbd.CF--O--›CF.sub.2 CF(CF.sub.3)!--O--CF.sub.2 CF.sub.2 --SO.sub.2 F (PSEPVE)) and has an equivalent weight of approximately 1070. The microcomposite product of the present invention can be converted to a metal cation-exchanged material, as described by Waller (Catal. Rev. Sci. Eng. 28(1), 1-12 (1986)) for PFIEP resins. Such materials are also useful as catalysts. Traditionally, olefin isomerization and alkylation with paraffins have been catalyzed by liquid mineral acids such as H.sub.2 SO.sub.4, HF or AlCl.sub.3. Environmental concerns associated with corrosive mineral acid catalysts have encouraged process changes and the development of solid-bed catalyst processes. It is especially desirable to convert 1-butene to 2-butenes prior to use in the HF catalyzed alkylation process because the quality of the alkylates from 2-butenes (96-98 research octane number (RON) are significantly better than that from the 1-butene feed (87-89 RON). Extensive studies have been carried out on the solid acid catalyzed 1-butene isomerization to 2-butenes and to isobutene. 1-Butene isomerization to 2-butenes has been widely used as a model reaction of characterizing solid acid catalysts as well. It is clear that 1-butene isomerization to 2-butenes is not a very demanding reaction in terms of acid strength; several of solid acid are capable of catalyzing this isomerization involving the double bond shifting reaction. However, there remain important incentives for developing catalysts that can operate efficiently at lower temperatures. First, competing oligomerization reactions which not only result in yield losses, but also lead to catalyst deactivation generally become more significant at higher temperatures. Second, the equilibrium isomer distribution increasingly favors 2-butenes at lower temperatures. Various solid acid catalysts and even amorphous silica-alumina are capable of catalyzing the 1-butene isomerization to 2-butenes at near ambient temperatures, but rapid deactivation is frequently encountered. Acidic cation exchange resin, sulfonic styrene-divinylbenzene copolymer ("AMBERLYST 15.RTM.") was shown to be active for the 1-butene isomerization to 2-butenes (see T. Uematsu, Bull. Chem. Soc. Japan, 1972, 45, 3329). The present invention provides a process for the isomerization of an olefin comprising contacting said olefin at isomerization conditions with a catalytic amount of the microcomposite of the present invention. Olefin isomerization processes can be directed towards either skeletal isomerization, double bond isomerization or geometric isomerization. Skeletal isomerization is concerned with reorientation of the backbone of the carbon structure, for example 1-butene to isobutene. Double bond isomerization is concerned with relocation of the double bond between carbon atoms while maintaining the backbone of the carbon structure, for example 1-butene to 2-butene. Conversions between, for example cis and trans 2-pentenes, are known as geometric isomerization. The present invention provides primarily for double bond isomerization and includes some geometric isomerization. Skeletal isomerization is also provided to a limited degree at higher temperatures. Preferred olefins are C.sub.4 to C.sub.40 hydrocarbons having at least one double bond, the double bond(s) being located at a terminal end, an internal position or at both a terminal and internal position. Most preferred olefins have 4 to 20 carbon atoms. The olefin can be straight-chained (normal) or branched and may be a primary or secondary olefin and thus substituted with one or more groups that do not interfere with the isomerization reaction. Such substituted groups that do not interfer with the isomerization reaction could include alkyl, aryl, halide, alkoxy, esters, ethers, or thioethers. Groups that may interfere with the process would be alcohols, carboxylic acids, amines, aldhehydes and ketones. The porous microcomposite used in the present process is described in detail above and comprises a perfluorinated ion-exchange polymer containing pendant sulfonic and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide, wherein the weight percentage of perfluorinated ion-exchange polymer in the microcomposite is from about 0.1 to 90 percent, preferably from about 5 to about 80 percent, most preferably from about 5 to about 20 percent and wherein the size of the pores in the microcomposite is about 0.5 nm to about 75 nm. A preferred catalyst for the present olefin isomerization process is the microcomposite of the present invention wherein the perfluorinated ion-exchange polymer contains pendant sulfonic acid groups and wherein the metal oxide is silica, alumina, titania, germania, zirconia, alumino-silicate, zirconyl-silicate, chromic oxide and/or iron oxide. Most preferred is wherein the perfluorinated ion-exchange polymer is a "NAFION.RTM." PFIEP and the metal oxide is silica, the most preferred "NAFION.RTM." PFIEP having approximately 6.3 moles of tetrafluoroethylene (TFE) per mole of perfluoro perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) molecule (CF.sub.2 .dbd.CF--O--›CF.sub.2 CF(CF.sub.3)!--O--CF.sub.2 CF.sub.2 --SO.sub.2 F (PSEPVE)) and an equivalent weight of approximately 1070. In another embodiment, macroporosity (pore sizes about 75 to about 1000 nm) is also introduced into the microcomposite used in the present olefin isomerization process, resulting in the microcomposite having both increased surface area from the micropores and mesopores (0.5-75 nm) and enhanced accessibility resulting from the macropores (75-1000 nm). Contacting of the olefin with the catalyst can be effected by using the catalyst in a fixed-bed system, a moving-bed system, a fluidized-bed system, or in a batch-type operation. Reactants can contact the catalyst in the liquid phase, a mixed vapor-liquid phase, or a vapor phase. The reactants can contact the catalyst in the absence of hydrogen or in the presence of hydrogen in a molar ratio of hydrogen to olefin of from about 0.01 to about 10. "Absence of hydrogen" means that free or molecular hydrogen is substantially absent in the combined reactant feed to the process. Hydrogen, if present, can be supplied totally from outside the isomerization process, or the outside hydrogen may be supplemented by hydrogen separated from reaction products and recycled. Inert diluents such as helium, nitrogen, argon, methane, ethane and the like can be present either in association with hydrogen or in the absence of hydrogen. Although the principal isomerization reaction does not consume hydrogen, there can be net consumption of hydrogen in side reactions. The isomerization of olefins is well known to be limited by the thermodynamic equilibrium of the reacting species. Isomerization conditions for the present process comprise reaction temperatures generally in the range of about 0.degree. C. to about 300.degree. C., preferably from about 25.degree. C. to about 250.degree. C. Pressure can range from ambient for gas phase or pressure sufficient to keep reaction in the liquid phase. Reactor operating pressures usually will range from about one atmosphere to about 100 atmospheres, preferably from about one atmosphere to about 50 atmospheres. The amount of catalyst in the reactor will provide an overall weight hourly space velocity (WHSV) of from about 0.1 to 100 hr.sup.-1, preferably from about 0.1 to 10 hr.sup.-1 ; most preferably 0.1 to 2 hr.sup.-1. Long contact time during olefin isomerization can create undesirable by-products, such as oligomers. The process of the present invention utilizes short contact times which cuts down on the amount of undesirable by-products. Contact times for the present process range from about 0.01 hr to about 10 hrs; preferably 0.1 hr to about 5 hrs. Contact time may be reduced at higher temperatures. The particular product-recovery scheme employed is not deemed to be critical to the present invention; any recovery scheme known in the art may be used. Typically, the reactor effluent will be condensed and the hydrogen and inserts removed therefrom by flash separation. The condensed liquid product then is fractionated to remove light materials from the liquid product. The selected isomers may be separated from the liquid product by adsorption, fractionation, or extraction. Olefin isomerization is useful in converting compounds into isomers more useful for particular applications. Olefins with the double bond at a terminal end tend to be more reactive and are easy to oxidize which can cause problems with their storage. Therefore, a shift to a more stable form can be desirable. A high rate of conversion is found using the microcomposite of the present invention. Data in FIG. 1 shows that the microcomposite is very efficient for the 1-butene to 2-butenes isomerization reaction under mild conditions. Even at 50.degree. C., near thermodynamic equilibrium values are obtained, which at 50.degree. C. are 4.1%, 70.5% and 25.4% for 1-butene , trans-2-butene and cis-2-butene, respectively, and the experimental data are 6.6%, 66.9% and 26.5%, respectively at WHSV of 1-butene of 1 hr.sup.-1. The effective activation energy for 1-butene isomerization to 2-butenes was determined to be 16.0 kcal/mol over the 13 wt % "NAFION.RTM." PFIEP/silica microcomposite used (see Example 58). Comparisons performed in Example 57 show that "NAFION.RTM." NR50 at 50.degree. C. produced less than 1% conversion of the 1-butene, and at a temperature which could effectively catalyze the butene (200.degree. C.) Significant oligomers are also formed. A study on the effect of temperature was carried out with a very diluted feed of 1-butene and at very low WHSV of 1-butene (see Table 4a, Example 58). Since near equilibrium n-butene distribution was obtained at 50.degree. C., the main interest was on the isobutene formation. However, extremely small amounts, well below the equilibrium concentration, of isobutene was formed even at the highest temperature employed (250.degree. C.). Due to the very low WHSV of 1-butene employed (Table 4a), the oligomers formed were quite pronounced. However, oligomers as well as isobutene formed over the microcomposite catalyst were less than that produced from the "NAFION.RTM." NR50 beads catalyst under the same reaction conditions (see Table 2a, Example 57), and they are both in negligible amounts at low temperatures (<100.degree. C.). Even though no pronounced catalyst deactivation was observed over more than 12 hr for the 1-butene isomerization to 2-butenes, the formation of isobutene and oligomers decreased rather rapidly at temperatures>100.degree. C. The data listed in the Tables are obtained after about one hour on stream in all cases. These results suggest that isobutene could be formed through the cracking of butene oligomers which are favored at this temperature and low WHSV or 1-butene. Overall, the extremely low surface area "NAFION.RTM." NR50 beads result in low activity for the 1-butene isomerization under the reaction conditions employed. However, the intrinsic isomerization activity of the active sites in "NAFION.RTM." is high and when present in a more accessible microstructure it becomes a very effective catalyst. Very high catalytic activity was observed for the 13 wt % "NAFION.RTM." PFIEP/silica microcomposite material for which equilibrium distribution of n-butene can be readily obtained at 50.degree. C. and is about 5-6 times more active than the "AMBERLYST 15.RTM." catalyst. The microcomposite product of the present invention is useful in a range of catalytic reactions as described above. For some of these reactions, some brown coloration may form upon the catalyst. Catalysts of the present invention can be regenerated by treatment with an acid, for example nitric acid. The microcomposite catalyst is contacted with the acid and then stirred at a temperature ranging from about 15.degree. C. to about 100.degree. C. for about 1 hr to about 26 hrs. Subsequent washing with de-ionized water is used to remove excess acid. The catalyst is then dried at a temperature ranging from about 100.degree. C. to about 200.degree. C., preferably under vacuum for about 1 hr to about 60 hrs to yield the regenerated catalyst. |
| PATENT EXAMPLES | This data is not available for free |
| PATENT PHOTOCOPY | Available on request |
|
Want more information ? Interested in the hidden information ? Click here and do your request. |