| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 09.01 |
| PATENT GRANT DATE | 04.09.01 |
| PATENT TITLE |
Hydroperoxide decomposition process |
| PATENT ABSTRACT |
An improved process for decomposing alkyl or aromatic hydroperoxides to form a decomposition reaction mixture containing the corresponding alcohol and ketone. The improvement relates to decomposing the hydroperoxide by contacting the hydroperoxide with a catalytic amount of a heterogenous catalyst of Au, Ag, Cu or a sol-gel compound containing particular combinations of Fe, Ni, Cr, Co, Zr, Ta, Si, Mg, Nb, Al and Ti wherein certain of those metals have been combined with an oxide, such as an inorganic matrix of hydroxides or oxides, or combinations thereof. The catalysts may also optionally be supported on a suitable support member and used in the presence of an additional metal. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 02.02.00 |
| PATENT CLAIMS |
1. An improved process for decomposing a hydroperoxide to form a decomposition reaction mixture containing a corresponding alcohol and ketone, the improvement comprising decomposing a hydroperoxide by contacting the hydroperoxide with a catalytic amount of a heterogeneous catalyst selected from the group consisting of elemental gold, silver, and copper, wherein 0 to 18% of one or more metals selected from Periodic Group VIII is/are also present with the heterogeneous catalyst. 2. The process according to claim 1 wherein the heterogeneous catalyst is supported on a catalyst support member. 3. The process according to claim 2 wherein the catalyst support member is selected from the group consisting of SiO.sub.2, Al.sub.2 O.sub.3, carbon, TiO.sub.2, MgO, and zirconia. 4. The process according to claim 1 wherein the hydroperoxide is cyclohexylhydroperoxide. 5. The process according to claim 1 wherein the decomposition reaction temperature is from about 80.degree. C. to about 170.degree. C., and decomposition reaction pressure is from about 69 kPa to about 2760 kPa. 6. The process according to claim 5 wherein the reaction pressure is from about 276 kPa to about 1380 kPa. 7. The process according to claim 1 wherein the reaction mixture contains from about 0.5 to about 100 percent by weight cyclohexyl hydroperoxide. 8. The process according to claim 1 wherein the process is run in the presence of cyclohexane. 9. The process according to claim 1 wherein the process is run in the presence of added oxygen. 10. The process according to claim 2 wherein the heterogeneous catalyst is gold. 11. The process according to claim 10 wherein the gold is supported on zirconia or alumina. 12. The process according to claim 10 wherein the gold is from about 0.1 to about 10 wt. percent of the catalyst and support member. 13. The process according to claim 10 wherein the gold is present on the support member as well-dispersed particles having a diameter from about 3 nm to about 15 nm. 14. The process according to claim 1 wherein the Group VIII metal is Pd or Pt. 15. The process according to claim 1 wherein the process is run in the presence of hydrogen. 16. The process of claim 1 wherein the catalyst support member is alumina. 17. An improved process for decomposing a hydroperoxide to form a decomposition reaction mixture containing a corresponding alcohol and ketone, the improvement comprising decomposing a hydroperoxide by contacting the hydroperoxide with a catalytic amount of a heterogeneous catalyst, prepared by a sol-gel method, comprised of (a) one or more members selected from a first group consisting of Au, Cr, Co and Ti and (b) one or more members selected from a second group consisting of Fe, Ni, Zr, Ta, Nb, Al, Mg and Ti, wherein the selected members of (b) are combined with an oxide and wherein members of the first group cannot be the same as members of the second group. 18. The process according to claim 17 wherein the heterogeneous catalyst contains Cr and/or Co. 19. The process according to claim 18 wherein the heterogeneous catalyst comprises Au and Cr. 20. The process according to claim 17 wherein the oxide is an inorganic matrix of hydroxides or oxides, or combinations thereof. 21. The process according to claim 17 wherein the hydroperoxide is cyclohexylhydroperoxide. 22. The process according to claim 17 wherein the process is run in the presence of added oxygen. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The invention generally relates to an improved catalytic process for decomposing alkyl or aromatic hydroperoxides to form a mixture containing the corresponding alcohol and ketone. In particular, the invention relates to decomposing a hydroperoxide by contacting it with a catalytic amount of a heterogenous catalyst of Au, Ag, Cu or a sol-gel compound containing particular combinations of Fe, Ni, Cr, Co, Zr, Ta, Si, Ti, Nb, Al and Mg, wherein certain of those metals have been combined with an oxide. BACKGROUND OF THE INVENTION Industrial processes for the production of mixtures of cyclohexanol and cyclohexanone from cyclohexane are currently of considerable commercial significance and are well described in the patent literature. In accordance with typical industrial practice, cyclohexane is oxidized to form a reaction mixture containing cyclohexyl hydroperoxide (CHHP). The resulting CHHP is decomposed, optionally in the presence of a catalyst, to form a reaction mixture containing cyclohexanol and cyclohexanone. In the industry, such a mixture is known as a K/A (ketone/alcohol) mixture, and can be readily oxidized to produce adipic acid, which is an important reactant in processes for preparing certain condensation polymers, notably polyamides. Due to the large volumes of adipic acid consumed in these and other processes, improvements in processes for producing adipic acid and its precursors can be used to provide beneficial cost advantages. Druliner et al., U.S. Pat. No. 4,326,084, disclose an improved catalytic process for oxidizing cyclohexane to form a reaction mixture containing CHHP, and for subsequently decomposing the resulting CHHP to form a mixture containing K and A. The improvement involves the use of certain transition metal complexes of 1,3-bis(2-pyridylimino)isoindolines as catalysts for cyclohexane oxidation and CHHP decomposition. According to this patent, these catalysts demonstrate longer catalyst life, higher CHHP conversion to K and A, operability at lower temperatures (80-160.degree. C.), and reduced formation of insoluble metal-containing solids, relative to results obtained with certain cobalt(II) fatty acid salts, e.g., cobalt 2-ethylhexanoate. Druliner et al., U.S. Pat. No. 4,503,257, disclose another improved catalytic process for oxidizing cyclohexane to form a reaction mixture containing CHHP, and for subsequently decomposing the resulting CHHP to form a mixture containing K and A. This improvement involves the use of Co.sub.3 O.sub.4, MnO.sub.2, or Fe.sub.3 O.sub.4 applied to a suitable solid support as catalysts for cyclohexane oxidation and CHHP decomposition at a temperature from about 80.degree. C. to about 130.degree. C., in the presence of molecular oxygen. Sanderson et al., U.S. Pat. No. 5,414,163, disclose a process for preparing t-butyl alcohol from t-butyl hydroperoxide in the liquid phase over catalytically effective amounts of titania, zirconia, or mixtures thereof. Sanderson et al., U.S. Pat. Nos. 5,414,141, 5,399,794 and 5,401,889, disclose a process for preparing t-butyl alcohol from t-butyl hydroperoxide in the liquid phase over catalytically effective amounts of palladium with gold as a dispersing agent supported on alumina. Druliner et al., U.S. provisional application No. 60/025,368 filed Sep. 3, 1996 (now PCT US97/15332 filed Sep. 2, 1997), disclose decomposing a hydroperoxide by contacting it with a catalytic amount of a heterogenous catalyst of Zr, Nb, Hf and Ti hydroxides or oxides. Preferably, the catalyst is supported on SiO.sub.2, Al.sub.2 O.sub.3, carbon or TiO.sub.2. Further improvements and options are needed for hydroperoxide decomposition to K/A mixtures in order to overcome the deficiencies inherent in the prior art. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the detailed description which hereinafter follows. SUMMARY OF THE INVENTION In accordance with the present invention, an improved process is provided in which a hydroperoxide is decomposed to form a decomposition reaction mixture containing a corresponding alcohol and ketone. The improvement comprises decomposing hydroperoxide by contacting a hydroperoxide with a catalytic amount of a heterogenous catalyst selected from the group consisting of (1) Au (gold), (2) Ag (silver), (3) Cu (copper) and (4) sol-gel compounds comprised of (a) one or more members selected from a first group consisting of Cr, Co and Ti and (b) one or more members selected from a second group consisting of Fe, Ni, Zr, Ta, Nb, Si, Al, Mg and Ti, wherein the selected members of (b) are combined with an oxide and wherein members of the first group cannot be the same as members of the second group. Preferably, an inorganic matrix of hydroxides or oxides, or combinations thereof, is used as the oxide. Moreover, the catalysts are optionally supported on a suitable support member, such as SiO.sub.2, Al.sub.2 O.sub.3, carbon, zirconia, MgO or TiO.sub.2. Zirconia and alumina are preferred supports. Where the catalyst is gold, one or more metals selected from the group consisting of members of Periodic Group VIII may additionally be present. Preferably the metal is Pt or Pd. When one or more additional metals are present, the process may optionally be run in the presence of hydrogen gas. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides an improved process for conducting a hydroperoxide decomposition step in an industrial process in which an alkyl or aromatic compound is oxidized to form a mixture of the corresponding alcohol and ketone. In particular, cyclohexane can be oxidized to form a mixture containing cyclohexanol (A) and cyclohexanone (K). The industrial process involves two steps: first, cyclohexane is oxidized, forming a reaction mixture containing CHHP; second, CHHP is decomposed, forming a mixture containing K and A. As previously mentioned, processes for the oxidation of cyclohexane are well known in the literature and available to those skilled in the art. Advantages of the present heterogenous catalytic process, relative to processes employing homogenous metal catalysts, such as metal salts or metal/ligand mixtures, include longer catalyst life, improved yields of useful products, and the absence of soluble metal compounds. The improved process can also be used for the decomposition of other alkane or aromatic hydroperoxides, for example, t-butyl hydroperoxide, cyclododecylhydroperoxide and cumene hydroperoxide. The CHHP decomposition process can be performed under a wide variety of conditions and in a wide variety of solvents, including cyclohexane itself. Since CHHP is typically produced industrially as a solution in cyclohexane from catalytic oxidation of cyclohexane, a convenient and preferred solvent for the decomposition process of the invention is cyclohexane. Such a mixture can be used as received from the first step of the cyclohexane oxidation process or after some of the constituents have been removed by known processes such as distillation or aqueous extraction to remove carboxylic acids and other impurities. The preferred concentration of CHHP in the CHHP decomposition feed mixture can range from about 0.5% by weight to 100% (i.e., neat). In the industrially practiced route, the preferred range is from about 0.5% to about 3% by weight. Suitable reaction temperatures for the process of the invention range from about 80.degree. C. to about 170.degree. C. Temperatures from about 110.degree. C. to about 130.degree. C. are typically preferred. Reaction pressures can preferably range from about 69 kPa to about 2760 kPa (10-400 psi) pressure, and pressures from about 276 kPa to about 1380 kPa (40-200 psi) are more preferred. Reaction time varies in inverse relation to reaction temperature, and typically ranges from about 2 to about 30 minutes. As noted previously, the heterogenous catalysts of the invention include Au, Ag, Cu (including, but not limited to, Au, Ag and Cu sol-gel compounds) and certain non-Au/Ag/Cu sol-gel compounds, preferably applied to suitable solid supports. The inventive process may also be performed using Au, Ag or Cu in the presence of other metals (e.g., Pd). The metal to support percentage can vary from about 0.01 to about 50 percent by weight, and is preferably about 0.1 to about 10 wt. percent. Suitable, presently preferred supports include SiO.sub.2 (silica), Al.sub.2 O.sub.3 (alumina), C (carbon), TiO.sub.2 (titania), MgO (magnesia) or ZrO.sub.2 (zirconia). Zirconia and alumina are particularly preferred supports, and Au supported on alumina is a particularly preferred catalyst of the invention. Some of the heterogenous catalysts of the invention can be obtained already prepared from manufacturers, or they can be prepared from suitable starting materials using methods known in the art. These methods can include sol-gel techniques as described in more detail below for preparing both Au/Ag/Cu sol-gel compounds and other non-Au/Ag/Cu sol-gel compounds. Supported gold catalysts can be prepared by any standard procedure known to give well-dispersed gold, such as evaporative techniques or coatings from colloidal dispersions. In particular, ultra-fine particle sized gold is preferred. Such small particulate gold (often smaller than 10 nm) can be prepared according to Haruta, M., "Size-and Support-Dependency in the Catalysis of Gold", Catalysis Today 36 (1997) 153-166 and Tsubota et al., Preparation of Catalysts V, pp. 695-704 (1991). Such gold preparations produce samples that are purple-pink in color instead of the typical bronze color associated with gold and result in highly dispersed gold catalysts when placed on a suitable support member. These highly dispersed gold particles typically are from about 3 nm to about 15 nm in diameter. The catalyst solid support, including SiO.sub.2, Al.sub.2 O.sub.3, carbon, MgO, zirconia, or TiO.sub.2, can be amorphous or crystalline, or a mixture of amorphous and crystalline forms. Selection of an optimal average particle size for the catalyst supports will depend upon such process parameters as reactor residence time and desired reactor flow rates. Generally, the average particle size selected will vary from about 0.005 mm to about 5 mm. Catalysts having a surface area larger than 10 m.sup.2 /g are preferred since increased surface area of the catalyst has a direct correlation with increased decomposition rates in batch experiments. Supports having much larger surface areas can also be employed, but inherent brittleness of high-surface area catalysts, and attendant problems in maintaining an acceptable particle size distribution, will establish a practical upper limit upon catalyst support surface area. A preferred support is alumina; more preferred is .alpha.-alumina and .gamma.-alumina. Other catalysts useful in the present invention are comprised of certain metals (including metal ions) combined with an oxide, such as an inorganic matrix of hydroxides or oxides, or combinations thereof The metals include Fe, Ni, Cr, Co, Zr, Ta, Nb, Al, Si, Ti and Mg, present in combinations as set forth before. The mole percentage of metals in the matrix can vary, as can the number of different metals and their relative ratios. They also may have variable hydroxide content, which can depend on calcination temperature, if performed, and other parameters. The transition metals Co and Cr can be present as inorganic salts while Fe, Ni, Zr, Ta, Nb, Si, Al, Ti and Mg can be present as an oxide, a hydroxide, or combinations thereof. (Note that for simplification the corresponding anions are not shown for these cations in the formulae identified herein). Typical preparations involve sol-gel chemistry wherein the metals are co-hydrolyzed and/or entrapped within an inorganic matrix. Better dispersion and uniformity of the metal can be obtained compared to that normally attainable using more conventional synthetic methods. The inorganic matrix can optionally be supported on an appropriate support member, such as SiO.sub.2, Al.sub.2 O.sub.3, ZrO.sub.2, carbon, MgO, or TiO.sub.2. Preferred catalysts of this type are those containing Cr and/or Co. A "sol-gel technique" is a process wherein a free flowing fluid solution, "sol", is first prepared by dissolving suitable precursor materials such as colloids, alkoxides or metal salts in a solvent. The "sol" is then dosed with a reagent to initiate reactive polymerization of the precursor. A typical example is tetraethoxyorthosilicate (TEOS) dissolved in ethanol. Water, with trace acid or base as catalyst to initiate hydrolysis, is added. As polymerization and crosslinking proceeds, the free flowing "sol" increases in viscosity and can eventually set to a rigid "gel". The "gel" consists of a crosslinked network of the desired material which encapsulates the original solvent within its open porous structure. The "gel" may then be dried, typically by either simple heating in a flow of dry air to produce a xerogel or the entrapped solvent may be removed by displacement with a supercritical fluid such as liquid CO.sub.2 to produce an aerogel. These aerogels and xerogels may be optionally calcined at elevated temperatures (>200.degree. C.) which results in products which typically have very porous structures and concomitantly high surface areas. In practice of the invention, the catalysts can be contacted with CHHP by formulation into a catalyst bed, which is arranged to provide intimate contact between catalysts and reactants. Alternatively, catalysts can be slurried with reaction mixtures using techniques known in the art. The process of the invention is suitable for batch or for continuous CHHP decomposition processes. These processes can be performed under a wide variety of conditions. Adding air or a mixture of air and inert gases to CHHP decomposition mixtures provides higher conversions of process reactants to K and A, since some cyclohexane is oxidized directly to K and A, in addition to K and A being formed by CHHP decomposition. This ancillary process is known as "cyclohexane participation", and is described in detail in Druliner et al., U.S. Pat. No. 4,326,084, the entire contents of which are incorporated by reference herein. Other gases may also be added or co-fed to the reaction mixture as needed. Inert gases such as nitrogen may also be added to the reaction alone or in combination with other gases. The results of the CHHP decomposition reaction, such as the K/A ratio or conversion rate, can be adjusted by choice of catalyst support, gases added to the reaction mixture, or metals added to the heterogeneous catalysts of the invention. Preferably, metals added to the heterogenous catalysts of the invention are for use as promoters, synergist additives, or co-catalysts are selected from Periodic Group VIII, hereby defined as Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt. Most preferred is Pd and Pt. One preferred gas that can be added to the reaction mixture is hydrogen. An advantage of the addition of hydrogen is that the K/A ratio can be varied according to need. The addition of hydrogen can also convert impurities or by-products of the reactions, such as benzene, to more desirable products. The hydrogen preferably is added to the process when the catalyst is gold with additional metals present. The process of the present invention is further illustrated by the following non-limiting examples. In the examples, all temperatures are in degrees Celsius and all percentages are by weight unless otherwise indicated. |
| PATENT EXAMPLES | This data is not available for free |
| PATENT PHOTOCOPY | Available on request |
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