Isomerization of monocyclic alkyl aromatic hydrocarbons

Abstract

A process is provided for isomerization of monocyclic alkyl aromatic hydrocarbons in a reaction zone maintained under conditions such that said isomerization is accomplished in the vapor phase.

What is claimed is: 
     
       1. A process for effecting catalytic isomerization of xylenes which comprises contacting said xylenes in the vapor phase with hydrogen at a temperature of from about 450° to about 900° F., a pressure of from about 50 psig to about 500 psig, a hydrogen/hydrocarbon mole ratio of from about 0.1 to about 100 and a weight hourly space velocity of from about 0.1 to about 200 in the presence of from about 3 to about 30 combined weight percent, based upon weight of the xylene feed, of diluent of toluene and C 9  + recycle material and a crystalline aluminosilicate zeolite characterized by a silica/alumina mole ratio of greater than 12 and a constraint index within the approximate range of 1 to 12 and containing cations which are selected from the group consisting of iron, nickel and cobalt. 
     
     
       2. The process of claim 1 wherein said zeolite is ZSM-5, ZSM-11, ZSM-12, ZSM-35 or ZSM-38. 
     
     
       3. The process of claim 2 wherein said zeolite is ZSM-5. 
     
     
       4. The process of claim 1 wherein said zeolite is combined in an amount of from about 30 to about 90 weight percent in a binder therefor. 
     
     
       5. The process of claim 4 wherein said binder is alumina. 
     
     
       6. The process of claim 2 wherein said zeolite is combined in an amount of from about 30 to about 90 weight percent in a binder therefor. 
     
     
       7. The process of claim 6 wherein said binder is alumina. 
     
     
       8. The process of claim 1 wherein said cations are nickel. 
     
     
       9. The process of claim 1 wherein said diluent is present at from about 5 to about 25 weight percent of the xylene mixture feed. 
     
     
       10. The process of claim 2 wherein said diluent is present at from about 5 to about 25 weight percent of the xylene mixture feed. .Iadd. 
     
     
       11.  The process of claim 1 wherein said zeolite is combined in an amount from about 30 to about 90 weight percent with a calcined α-alumina monohydrate binder. .Iaddend. .Iadd.12. The process of claim 11 wherein said zeolite has a silica to alumina ratio of at least 30..Iaddend. .Iadd.13. The process of claim 12 wherein said zeolite has a silica to alumina ratio from at least about 30 to at least about 350..Iaddend. .Iadd.14. The process of claim 13 where said zeolite consists essentially of ZSM-5..Iaddend. .Iadd.15. The process of claim 14 wherein said zeolite is extruded with the alumina monohydrate and calcined to form a catalyst having about 65 weight percent zeolite and about 35 weight percent alumina binder..Iaddend.