Catalyst and process for the production of para-xylene

Patent metadata

Field	Value
Publication number	US-10647633-B2
Application number	US-201716075727-A
Country	US
Kind code	B2
Filing date	Jan 27, 2017
Priority date	Mar 25, 2016
Publication date	May 12, 2020
Grant date	May 12, 2020

Abstract

A fluidized bed process for producing para-xylene via toluene and/or benzene methylation with methanol using a dual function catalyst system. A first catalyst accomplishes the toluene and/or benzene methylation and a second catalyst converts the by-products of the methylation reaction or unconverted methylating agent, improves the yields of the desired products, or a combination thereof. The inclusion of the second catalyst can suppress the C1-C5 non-aromatic fraction by over 50% and significantly enhance the formation of aromatics.

First claim

The invention claimed is:

1. A process for producing para-xylene, the process comprising:
(a) providing a catalyst comprising core crystals of a first medium-pore size aluminosilicate zeolite having a pore size of about 5 to about 7 Angstroms and a discontinuous layer of shell crystals of a second medium-pore size aluminosilicate zeolite covering at least a portion of the external surface of the core crystals in a fluidized bed reactor, wherein the first medium-pore size aluminosilicate zeolite has a lower silica/alumina molar ratio than that of the second medium-pore size aluminosilicate zeolite;
(b) alkylating C 6+ aromatic hydrocarbons with an alkylating agent selected from methanol, dimethyl ether, and mixtures thereof, on contacting the shell crystals under conditions including a temperature of at least 400° C. to produce a mixture comprising olefins and/or paraffins, para-xylene, unconverted alkylating agent, and unconverted C6+ aromatics hydrocarbons; and
(c) converting the olefins and/or the paraffins formed in step (b), unconverted alkylating agent, and unconverted C 6+ aromatic hydrocarbons to para-xylene on contacting the core crystals.

2. The process of claim 1 , wherein the second medium-pore size aluminosilicate zeolite comprises ZSM-5 having a silica/alumina molar ratio of at least 200, as measured prior to any steaming of the catalyst.

3. The process of claim 1 ,
wherein the second medium-pore size aluminosilicate zeolite comprises ZSM-5 and phosphorus or a compound thereof;
wherein (a) further comprises steaming the catalyst at a temperature of at least 900° C. so that the catalyst has a Diffusion Parameter for 2,2 dimethylbutane of about 0.1-15 sec −1 when measured at a temperature of 120° C. and a 2,2 dimethylbutane pressure of 60 torr (8 kPa).

4. The process of claim 1 , wherein the first medium-pore size aluminosilicate zeolite comprises ZSM-5 having a lower silica/alumina molar ratio than that of the second medium-pore size aluminosilicate zeolite.

5. The process of claim 1 , wherein the first medium-pore size aluminosilicate zeolite comprises ZSM-5 having a silica/alumina molar ratio of about 10-100, as measured prior to any steaming of the catalyst, and about 0.01 to 2 wt % of at least one Group 6-14 element.

6. The process of claim 5 , wherein the first medium-pore size aluminosilicate zeolite comprises from about 0.8-1.2 wt % of the Group 6-14 element.

7. The process of claim 5 , wherein the Group 6-14 element is selected from the group consisting of Zn, Ga, Cu, Ag or Pt.

8. The process of claim 7 , wherein the Group 6-14 element comprises Zn or Ga.

9. The process of claim 1 , wherein the catalyst further comprises a binder.

10. The process of claim 9 , wherein the binder comprises silica and/or clay.

11. The process of claim 9 , wherein the catalyst contains from 75 to 90 wt % binder.

12. The process of claim 1 , wherein the second medium-pore size aluminosilicate zeolite has been steamed at a temperature of at least 900° C. for between about 10 minutes and about 1.5 hours.

13. The process of claim 1 , wherein said conditions in (b) also include a temperature between about 500 and 700° C., a total reactor pressure of between about 1 atmosphere and 1000 psig (100 and 7000 kPa), a weight hourly space velocity between about 0.5 and about 1000 and a molar ratio of toluene to methanol of at least about 0.2.

14. A process for producing para-xylene, the process comprising:
(a) providing a core-shell catalyst comprising a discontinuous layer of shell crystals covering at least a portion of the external surface of core crystals in a fluidized bed reactor,
wherein the shell crystals comprise ZSM-5 having a silica/alumina molar ratio of at least 200, as measured prior to any steaming of the catalyst, and phosphorus or a compound thereof, wherein the catalyst has been steamed at a temperature of at least 900° C., wherein said steamed catalyst has a Diffusion Parameter for 2,2 dimethylbutane of about 0.1-15 sec −1 when measured at a temperature of 120° C. and a 2,2 dimethylbutane pressure of 60 torr (8 kPa),
wherein the core crystals comprise ZSM-5, and the ZSM-5 of the core crystals has a lower silica/alumina molar ratio than that of the shell crystals;
(b) alkylating C 6+ aromatic hydrocarbons with an alkylating agent selected from methanol, dimethyl ether, and mixtures thereof, on contacting the shell crystals to produce a mixture comprising olefins and/or paraffins, para-xylene, unconverted alkylating agent, and unconverted C6+ aromatics hydrocarbons; and
(c) converting the olefins and/or the paraffins formed in step (b), unconverted alkylating agent, and unconverted C 6+ aromatic hydrocarbons to para-xylene on contacting the core crystals.

15. The process of claim 14 , wherein the core crystals comprise ZSM-5 having a silica/alumina molar ratio of about 10-100, as measured prior to any steaming of the catalyst, and about 0.01 to 2 wt % of at least one Group 6-14 element.

16. The process of claim 14 , wherein the core crystals comprise from about 0.8-1.2 wt % of the Group 6-14 element and wherein the Group 6-14 element is selected from the group consisting of Zn, Ga, Cu, Ag or Pt.

17. The process of claim 14 , wherein the catalyst further comprises a binder.

18. The process of claim 14 , wherein said conditions in (b) also include a temperature between about 500 and 700° C., a total reactor pressure of between about 1 atmosphere and 1000 psig (100 and 7000 kPa), a weight hourly space velocity between about 0.5 and about 1000 and a molar ratio of toluene to methanol of at least about 0.2.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Soultanidis Nikolaos
• Detjen Todd E
• Weigel Scott J

Classifications

• B01J2229/62

  in or on other molecular sieves · CPC title

• B01J29/42

  containing iron group metals, noble metals or copper · CPC title

• C07C2/864 Primary

  the non-hydrocarbon is an alcohol · CPC title

• C07C2/865

  the non-hydrocarbon is an ether · CPC title

• B01J29/44

  Noble metals · CPC title