Patent EA-001597-B1 (EA)
Title: Process for isomerization of alkylaromatic hydrocarbons
Inventor: MOHR GARY D
IPC: C07C2/86
Filed: 1997-05-29
Abstract: 1. A process for isomerizing a feed containing isomerizable monocyclic alkylaromatic hydrocarbons, isomerizable bicyclic alkylaromatic hydrocarbons, or mixtures thereof comprising: contacting the feed under isomerization conversion conditions with a zeolite bound zeolite catalyst which containsless than 10% by weight of non-zeolitic binder based on the combined weight of first and second zeolite and comprises: (a) first crystals of a first zeolite of intermediate pore size; and (b) a binder comprising second crystals of a second zeolite. 2. The process recited in Claim 1 wherein the second crystals are intergrown and form at least a partial coating on the first crystals. 3. The process recited in Claim 1 or 2 wherein the first crystals have an average particle size of at least 0.1 micron and the second crystals have an average particle size less than that of the first crystals. 4. The process recited in Claim 3 wherein the first crystals have an average particle size of from 1 to 6 microns and the second crystals have an average particle size of from 0.1 to 0.5 microns. 5. The process recited in any preceding Claim wherein the structure types of the first zeolite and the second zeolite are independently MFI, MEL, MTW, MTT, FER, EUO or TON. 6. The process recited in Claim 5 wherein the first zeolite has an MFI structure. 7. The process recited in Claim 5 or 6 wherein the second zeolite has an MFI or MEL structure. 8. The process recited in any preceding Claim wherein the first zeolite is at least partially in the hydrogen form. 9. The process recited in any preceding Claim wherein the first zeolite and the second zeolite are independently characterized by a composition, expressed by following mole ratio: X2O3:(n)YO2, where X is aluminum, boron, and/or gallium, Y is silicon, tin and/or germanium and n is greater than 10. 10. The process recited in Claim 9 wherein the first zeolite has a silica to alumina mole ratio of from 70:1 to 700:1 or a silica to gallia mole ratio from 24:1 to 500:1. 11. The process recited in any preceding Claim wherein the first zeolite contains catalytically active sites. 12. The process recited in any preceding Claim wherein the second zeolite has less acidity than the first zeolite, and is preferably substantially nonacidic. 13. The process recited in any preceding Claim wherein the second zeolite is an aluminosilicate zeolite, a gallium silicate zeolite, or a boron silicate zeolite. 14. The process recited in Claim 13 wherein the second zeolite has a silica to alumina mole ratio greater than 200:1 or a silica to gallia mole ratio greater than 100:1, preferably greater than 200:1. 15. The process recited in Claim 13 or 14 wherein the second zeolite is silicalite or silicalite 2. 16. The process recited in any preceding Claim wherein the zeolite bound zeolite catalyst further comprises at least one catalytic hydrogenation metal. 17. The process recited in Claim 16 wherein the catalytic hydrogenation metal is a Group VIII metal. 18. The process recited in Claim 16 or 17 wherein the zeolite bound zeolite catalyst is preparable by a method that comprises providing a silica-bound aggregate comprising at least a portion of the catalytic hydrogenation metal and the first crystals of the first zeolite and converting same to the second zeolite. 19. The process recited in any preceding Claim wherein the zeolite bound zeolite catalyst is preparable by a method that comprises aging at elevated temperatures a silica-bound aggregate containing the first crystals of the first zeolite in an aqueous ionic solution containing hydroxy ions. 20. The process recited in any preceding Claim wherein the zeolite bound zeolite catalyst contains less than 5% by weight of non-zeolitic binder based on the combined weight of first and second zeolite. 21. The process recited in any preceding Claim wherein the zeolite bound zeolite catalyst does not contain non-zeolitic binder. 22. The process recited in any preceding Claim wherein the alkylaromatic hydrocarbons are selected from the group consisting of: (a) monocyclic alkylaromatic hydrocarbons represented by the formula:   wherein: each R<1> is independently an alkyl group having 1 to 4 carbon atoms; and x is 2 or 3; and (b) bicyclic alkylaromatic hydrocarbons represented by the formula:   wherein R<2> and R3 is each independently an alkyl group having 1 to 4 carbon atoms; and y and z is each independently 0, 1 or 2, provided that the sum of y and z is 2, 3, or 4. 23. The process recited in Claim 22 wherein the feed comprises monocyclic alkylaromatic hydrocarbons of formula I wherein R<1> is methyl or ethyl and x is 2. 24. The process recited in Claim 22 or 23 wherein the feed comprises  bicyclic alkylaromatic hydrocarbons of formula II wherein each of R<2> and R<3> is methyl, y is 1 and z is 1. 25. The process recited in any preceding Claim wherein the feed comprises an aromatic C8 mixture of ethylbenzene and xylenes in which the paraxylene concentration is at less than thermodynamic equilibrium. 26. The process recited in Claim 25 wherein in addition to being contacted with the zeolite bound zeolite catalyst, the feed is also contacted under conversion conditions with a second catalyst that is a xylene isomerization catalyst; and wherein the zeolite bound zeolite catalyst comprises an acidic first zeolite, a second zeolite having less acidity than the first zeolite, and an effective amount of a catalytic hydrogenation metal. 27. The process recited in Claim 26 wherein the feed is contacted with the zeolite bound zeolite catalyst before it is contacted with the second catalyst. 28. The process recited in Claim 26 or 27 wherein the zeolite bound zeolite catalyst and the second catalyst are located in separate catalyst beds. 29. The process recited in Claims 26 or 27 wherein the zeolite bound zeolite catalyst and the second catalyst are located in the same catalyst bed. 30. The process recited in any of Claims 26 to 29 wherein the zeolite bound zeolite catalyst and the second catalyst are located in the same reactor. 31. The process recited in any of Claims 25 to 30 wherein at least 30 percent of the ethylbenzene is converted. 32. The process recited in Claim 31 wherein at least 50% of the ethylbenzene is converted. 33. The process recited in any of Claims 26 to 32 wherein the second catalyst is a zeolite bound zeolite catalyst which does not contain significant amounts of non-zeolitic binder and comprises: (a) first crystals of an intermediate pore size first zeolite; and (b) binder comprising second crystals of a second zeolite having higher acidity than the first zeolite. 34. The process recited in Claim 33 wherein the second catalyst comprises an MFI structure type first zeolite; and an MFI or MEL structure type second zeolite. 35. The process recited in Claim 33 or 34 wherein the second catalyst further comprises an effective amount of at least one catalytic hydrogenation metal. 36. The process recited in any of Claims 26 to 32 wherein the second catalyst is an acidic non-zeolitic catalyst. 37. The process recited in any of Claims 26 to 32 wherein the second catalyst is a zeolite catalyst bound by amorphous material. 38. The process recited in any preceding Claim wherein the isomerization conditions comprise a temperature of from 204 degree  to 538 degree C (400 degree  to 1000 degree F) and/or a pressure of from 0.34 to 6.9 MPag (50 to 1000 psig) and/or a weight hourly space velocity of from 0.5 to 100 and/or a hydrogen/hydrocarbon molar ratio of from 0.1 to 10.