Method for producing zeolites with reduced surface acidity

• US 5,234,872 A
• Filed: 05/11/1992
• Issued: 08/10/1993
• Est. Priority Date: 05/11/1992
• Status: Expired due to Term

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Degnan, Thomas F., Apelian, Minas R., Fung, Anthony S.
• Primary Examiner(s): DEES, CARL
• Application Number:
  US07/881,281
• Time in Patent Office: 456 Days
• Field of Search: 502/85, 502/62
• US Class Current: 502/62
• CPC Class Codes: B01J 2229/12 to alter the outside of the crystallites, e.g. selectivation
• CPC Class Codes: B01J 2229/16 to increase the Si/Al ratio; Dealumination
• CPC Class Codes: B01J 2229/37 Acid treatment
• CPC Class Codes: B01J 29/06 Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
• CPC Class Codes: B01J 29/7007 Zeolite Beta

Abstract

A process for the selective surface dealumination of organic-containing zeolites by contacting the zeolite with dicarboxylic acid, such as oxalic acid. The treatment results in a reduction in surface acidity without a significant reduction in overall activity. The organic may be a directing agent used in the zeolite synthesis or introduced into the pores of the zeolite after thermal treatment.

Claims

1. A process for the selective surface dealumination of an organic-containing zeolite comprising contacting said zeolite with dicarboxylic acid for a sufficient time to effect at least about a 25% reduction in surface acidity with less than about 50% overall dealumination.

2. The process of claim 1 wherein said reduction in surface acidity is determined by dealkylation of tri-tertbutylbenzene.

3. The process of claim 1 wherein said organic-containing zeolite contains at least about 5 wt % of an organic material.

4. The process of claim 3 wherein said organic-containing zeolite contains at least about 10 wt % of an organic material.

5. The process of claim 1 wherein said organic is a directing agent used in synthesis of said organic-containing zeolite.

6. The process of claim 1 wherein said organic-containing zeolite is synthesized in the absence of an organic directing agent, said organic being introduced after thermal treatment.

7. The process of claim 1 wherein said organic is selected from the group consisting of n-propylamine cations, n-butylamine cations, n-ethylamine cations, tetraethylammonium cations, tetrapropylammonium cations, pyridine, alkyl substituted pyridines and organic phosphites.

8. The process of claim 1 wherein said organic-containing zeolite is selected from the group consisting of zeolite Beta, mordenite, zeolite Y, ZSM-20, ZSM-4, faujasite and ZSM-5.

9. The process of claim 1 wherein said organic-containing zeolite is unbound.

10. The process of claim 1 wherein said organic-containing zeolite is bound with an inorganic oxide binder prior to said selective surface dealumination.

11. The process of claim 1 wherein said surface acidity is reduced by at least about 40%.

12. The process of claim 1 wherein said surface acidity is reduced by at least about 45%.

13. The process of claim 1 wherein said overall dealumination is less than about 20%.

14. The process of claim 1 wherein said overall dealumination is less than about 10%.

15. The process of claim 1 wherein said dicarboxylic acid is in solution.

16. The process of claim 15 wherein said solution of dicarboxylic acid is at a volume ratio of solution to catalyst of at least about 1:

1.

17. The process of claim 1 wherein said dicarboxylic acid is an aqueous dicarboxylic acid solution.

18. The process of claim 1 wherein said dicarboxylic acid is in a concentration in the range of from about 0.01 to about 4M.

19. The process of claim 1 wherein said dicarboxylic acid is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, maleic, phthalic, isophthalic, terephthalic, fumaric, tartaric and mixtures thereof.

20. The process of claim 1 wherein said dicarboxylic acid is oxalic acid.

21. The process of claim 1 wherein said contacting is for a time of at least about 10 minutes.

22. The process of claim 1 wherein said contacting is at a temperature in the range of from about 60°

F. to about 200°

F.

24. The product of the process by claim 1.

23. A process for the selective surface dealumination of a zeolite containing at least about 5 wt % of an organic material comprising contacting the zeolite with oxalic acid for a sufficient time to effect at least about a 25% reduction in surface acidity with less than about 50% overall dealumination.

25. The product of the process by claim 23.

26. A process for the selective surface dealumination of an organic-containing zeolite comprising contacting said zeolite with dicarboxylic acid for a time in the range of about 10 minutes to about 1 hour to effect at least about a 25% reduction in surface acidity with less than about 50% overall dealumination.

27. A process for the selective surface dealumination of an organic-containing zeolite Beta comprising contacting said zeolite Beta with dicarboxylic acid for a sufficient time to effect at least about a 25% reduction in surface acidity with less than about 50% overall dealumination.

28. The zeolite Beta produced by the process of claim 27.