초록 ▼

The invention concerns a xylenes isomerization process for the production of equilibrium or near-equilibrium xylenes. The process utilizes a catalyst comprising HZSM-5 or MCM-49 and process conditions including a temperature of less than 295° C. and a pressure sufficient to maintain the xylenes in l

The invention concerns a xylenes isomerization process for the production of equilibrium or near-equilibrium xylenes. The process utilizes a catalyst comprising HZSM-5 or MCM-49 and process conditions including a temperature of less than 295° C. and a pressure sufficient to maintain the xylenes in liquid phase. In embodiments, the process can be operated in a continuous mode with ppm levels of dissolved H2 in the feed and in other embodiments in a cyclic mode without the H2 in feed but with periodic regenerations using a feed having low ppm levels of H2.

대표청구항 ▼

1. A process comprising contacting a feedstream including C8 aromatic hydrocarbons, said feedstream characterized by having 4 to 100 ppm levels of dissolved H2, wherein said feedstream is further characterized as paraxylene-lean relative to the equilibrium amount of paraxylene in xylenes, with a cat

1. A process comprising contacting a feedstream including C8 aromatic hydrocarbons, said feedstream characterized by having 4 to 100 ppm levels of dissolved H2, wherein said feedstream is further characterized as paraxylene-lean relative to the equilibrium amount of paraxylene in xylenes, with a catalyst suitable for isomerization of xylenes, in a reactor under conditions including a temperature of less than 295° C., and a pressure sufficient to maintain the xylenes in liquid phase, and isomerizing said xylenes in the liquid phase to obtain a product stream having an increased concentration of paraxylene relative to the concentration of paraxylene in said feedstream, wherein said catalyst comprises at least one of HZSM-5 and MCM-49, wherein said HZSM-5 is characterized by the following characteristics: an average crystal size of less than 0.1 microns;a mesoporous surface area (MSA) greater than 45 m2/g;a zeolite surface area (ZSA) to mesoporous surface area (MSA) ratio of less than 9;a silica/alumina ratio of 20 to 50 by weight;wherein said process is then operated in a cyclic mode with a feedstream comprising less than 4 ppm dissolved H2, and further wherein said catalyst is periodically regenerated by a step including contacting said catalyst with an H2-containing feedstream. 2. The process according to claim 1, wherein said reactor temperature is less than 280° C. 3. The process of claim 1, wherein said reactor is selected from a fixed bed reactor, a fluid bed reactor, a dense bed reactor, and a simulated moving bed reactor. 4. The process of claim 3, wherein said feedstream contacts said catalyst at a flow rate of 1 to 10 WHSV. 5. The process of claim 3, wherein said contacting is conducted with an up-flow mode of operation. 6. The process of claim 3, wherein said contacting is conducted with a down-flow mode of operation. 7. The process of claim 1, wherein said catalyst comprises 10 wt %-90 wt % of HZSM-5 zeolite. 8. The process of claim 1, wherein said catalyst comprises HZSM-5 formed by extrusion, using acetic acid as an extrusion aid.