Method and catalyst system for the production of para-xylene

Patent metadata

Field	Value
Publication number	US-10144006-B2
Application number	US-201514802631-A
Country	US
Kind code	B2
Filing date	Jul 17, 2015
Priority date	Aug 26, 2014
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A catalyst system is disclosed for producing para-xylene from a C 8 hydrocarbon mixture comprising ethylbenzene and at least one xylene isomer other than para-xylene. The catalyst system comprises a first catalyst bed and a second catalyst bed. The first catalyst bed comprises a first zeolite and a rhenium hydrogenation component. The first zeolite has a constraint index from 1 to 12, an average crystal size from 0.1 to 1 micron and has been selectivated to have an ortho-xylene sorption time of greater than 1200 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury. The second catalyst bed comprises a second zeolite and a rhenium hydrogenation component. The second zeolite has a constraint index ranging from 1 to 12 and an average crystal size of less than 0.1 micron.

First claim

The invention claimed is:

1. A process for producing para-xylene from a C 8 hydrocarbon mixture comprising ethylbenzene and at least one xylene isomer other than para-xylene, the process comprising:
(a) contacting the C 8 hydrocarbon mixture under ethylbenzene conversion conditions with a first catalyst, comprising a first zeolite comprising ZSM-5 and a hydrogenation component consisting essentially of rhenium, to form a xylene rich product that is depleted in ethylbenzene, wherein the first zeolite has an average crystal size from 0.1 to 1 micron and an alpha value of from greater than 500 to 700, and wherein the first zeolite has been selectivated with organosilicon compounds so as to have an ortho-xylene sorption time of greater than 1200 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury, wherein the first catalyst comprises a silica binder; and
(b) contacting the xylene rich product that is depleted in ethylbenzene under xylene isomerization conditions with a second catalyst comprising a second zeolite comprising ZSM-5 and a hydrogenation component consisting essentially of rhenium, to obtain a para-xylene product, wherein the second zeolite has a constraint index ranging from 1 to 12, an average crystal size of less than 0.1 micron, and an alpha value of from greater than 100 to less than 300, and wherein the second zeolite has an ortho-xylene sorption time of less than 50 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury,
wherein the ethylbenzene conversion conditions comprise a temperature less than about 750° F. (399° C.).

2. The process of claim 1 , wherein the ethylbenzene conversion conditions comprise a pressure from 0 to 1,000 psig (100 to 7,000 kPa-a), a weight hourly space velocity (WHSV) from 0.5 to 100 hr −1 , and a H 2 /HC mole ratio from 0.1 to 10.

3. The process of claim 1 , wherein the xylene isomerization conditions comprise a temperature from 570 to 900° F. (299 to 482° C.), a pressure from 100 to 600 psig (696 to 4,238 kPa-a), a weight hourly space velocity (WHSV) from 1 to 50 hr −1 , and a H 2 /HC mole ratio from 0.5 to 5.

4. The process of claim 1 , wherein the second zeolite has an average crystal size of from 0.02 to 0.05 micron.

5. The process of claim 1 , wherein the first zeolite has been selectivated so as to have an ortho-xylene sorption time from 2,000 to 5,000 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury.

6. The process of claim 1 , wherein the first zeolite has been selectivated by multiple treatments each comprising contacting the first zeolite with an organosilicon selectivating agent to obtain a selectivated first zeolite and subsequently calcining the selectivated first zeolite.

7. A process for producing para-xylene from a C 8 hydrocarbon mixture comprising ethylbenzene and at least one xylene isomer other than para-xylene, the process comprising:
(a) contacting the C 8 hydrocarbon mixture under ethylbenzene conversion conditions with a first catalyst, comprising a first zeolite comprising ZSM-5 and a hydrogenation component comprising rhenium, to form a xylene rich product that is depleted in ethylbenzene, wherein the first zeolite has an average crystal size from 0.1 to 1 micron, an alpha value of from greater than 500 to 700, and a silica to alumina molar ratio of less than 50, and wherein the first zeolite has been selectivated with organosilicon compounds so as to have an ortho-xylene sorption time of greater than 1200 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury, wherein the first catalyst comprises a silica binder; and
(b) contacting the xylene rich product that is depleted in ethylbenzene under xylene isomerization conditions with a second catalyst comprising a second zeolite comprising ZSM-5 and a hydrogenation component comprising rhenium, to obtain a para-xylene product, wherein the second zeolite has a constraint index ranging from 1 to 12, an average crystal size of less than 0.1 micron, an alpha value from 100 to less than 300, and a silica to alumina molar ratio of greater than or equal to 50, and wherein the second zeolite has an ortho-xylene sorption time of less than 50 minutes based on its capacity to sorb 30% of the equilibrium capacity of ortho-xylene at 120° C. and an ortho-xylene partial pressure of 4.5±0.8 mm of mercury,
wherein the ethylbenzene conversion conditions comprise a temperature less than about 750° F. (399° C.).

8. The process of claim 7 , wherein the silica to alumina molar ratio of the first zeolite is less than 30.

9. The process of claim 1 , wherein the second zeolite has an alpha value of about 100.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Cheng Jane C
• Zheng Xiaobo
• Nair Hari

Classifications

• C07C5/2708 Primary

  with crystalline alumino-silicates, e.g. molecular sieves · CPC title

• B01J35/023 Primary

  Operations & Transport · mapped topic

• C07C2529/48

  containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium · CPC title

• B01J19/0093

  Microreactors, e.g. miniaturised or microfabricated reactors (laboratory containers with capillary fluid transport in microfabricated channels or chambers B01L3/5027) · CPC title

• B01J2219/00873

  Heat exchange · CPC title