Alkylene oxide catalysts containing high silver content

• US 5,187,140 A
• Filed: 07/23/1990
• Issued: 02/16/1993
• Est. Priority Date: 10/18/1989
• Status: Expired due to Term

• Current Assignee: Dow Technology Investments LLC (Dow, Inc.)
• Original Assignee: Union Carbide Chemicals & Plastics Technology Corporation (Dow, Inc.)
• Inventors: Seyedmonir, Seyed R., Bhasin, Madan M., Thorsteinson, Erlind M.
• Primary Examiner(s): MCFARLANE, ANTHONY R
• Application Number:
  US07/556,828
• Time in Patent Office: 939 Days
• Field of Search: 502/347, 502/348, 502/344, 502/341, 502/224, 502/226, 502/231
• US Class Current: 502/348
• CPC Class Codes: B01J 23/50 Silver
• CPC Class Codes: B01J 23/66 Silver or gold
• CPC Class Codes: B01J 35/31 Density
• CPC Class Codes: B01J 35/612 less than 10 m2/g
• CPC Class Codes: B01J 35/635 0.5-1.0 ml/g
• CPC Class Codes: C07D 301/10 with catalysts containing silver or gold

Abstract

Catalysts for the epoxidation of alkene, especially ethylene, to the corresponding alkylene oxide, e.g., ethylene oxide, which catalysts contain a high silver content on carriers having a high surface area and a high pore volume are disclosed. Methods for making and using such catalysts are also disclosed.

Claims

1. A method for preparing a catalyst for the manufacture of alkylene oxide by the vapor phase epoxidation of alkene comprising:

a) providing a refractory solid support having a surface area of at least about 0.7 m² /g, a pore volume of at least about 0.5 cc/g, and a median pore diameter between about 1 and 25 microns, and wherein between about 10 and 25 volume percent of the pores of the support have a pore diameter between about 0.5 and 1 micron, at least about 10 volume percent of the pores of the support have a pore diameter between about 1 and 10 microns, and at least about 20 volume percent of the pores of the support have a pore volume between about 10 and 100 microns;

b) impregnating the support with a first impregnating solution containing dissolved silver compound;

c) removing the impregnated support from the first impregnating solution, said support containing silver compound, and subjecting the impregnated support to conditions which form silver metal from the silver compound;

d) impregnating the support with a second impregnating solution containing additional silver compound dissolved therein;

e) removing the impregnated support from the second impregnating solution, said support containing additional silver compound, and subjecting the impregnated support to conditions which form silver metal from the additional silver compound; and

f) repeating steps (d) and (e) until the amount of silver metal contained in the support is at least 30 percent by weight based on the entire weigh of the catalyst.

2. The method of claim 1, wherein the impregnating solutions contain at least one promoter which enhances the efficiency of the catalyst.

3. The method of claim 2, wherein the promoter is present only in the last silver impregnating solution.

4. The method of claim 3, wherein the promoter comprises molybdate.

5. The method of claim 1, wherein the support is contacted with a solution containing at least one promoter which enhances the efficiency of the catalyst.

6. The method of claim 1, wherein the concentration of silver compound is greater in the second impregnating solution than in the first impregnating solution.

7. The method of claim 1, wherein after impregnating the support with the first impregnating solution but before subjecting the impregnated support to conditions which form silver metal from the silver compound, the support is rinsed with a suitable solvent to remove occluded silver compound.

8. The method of claim 1, wherein the amount of impregnated silver metal is in the range of from about 30 to about 60 percent by weight based on the total weight of catalyst.

9. The method of claim 1, wherein the amount of impregnated silver metal is in the range of from about 35 to about 45 percent by weight based on the total weight of catalyst.

10. The method of claim 1, wherein the support has a lamellate morphology.

11. The method of claim 10, wherein the support is alpha-alumina.

12. The method of claim 11, wherein the support is at least 98% pure alpha-alumina.

13. The method of claim 1, wherein the support contains a fluorine-containing substance.

14. The method of claim 13, wherein the support containing a fluorine-containing substance has a lamellate morphology.

15. The method of claim 2, wherein the promoter is a compound comprising at least one element selected from groups 3b through 7b and groups 3a through 7a of the Periodic Table of the Elements.

16. The method of claim 2 wherein the promoter comprises a cation selected from the group consisting of alkali and alkaline earth metal cation.

17. The method of claim 15 in which the promoter enhances at least one of stability, efficiency and activity of the catalyst as determined under STANDARD ETHYLENE OXIDE PROCESS CONDITIONS.

18. The method of claim 15 wherein the promoter is selected from halides and oxyanions of elements other than oxygen having an atomic number of 7 to 83 and being from the groups 3b through 7b, inclusive, and 3a through 7a, inclusive, of the Periodic Table of the Elements.

19. The method of claim 18 in which the promoter is an oxyanion comprising sulfate.

20. The method of claim 18 in which the promoter is an oxyanion comprising molybdate.

21. A catalyst for the manufacture of alkylene oxide by the vapor phase epoxidation of alkene containing at least about 30 weight percent silver impregnated in at least two impregnation steps on an inert, refractory solid support having a surface area of at least about 0.7 m² /g and a pore volume of at least about 0.5 cc/g, a median pore diameter between about 1 and 25 microns, and wherein between about 10 and 25 volume percent of the pores of the support have a pore diameter between about 0.5 and 1 micron, at least about 10 volume percent of the pores of the support have a pore diameter between about 1 and 10 microns, and at least about 20 volume percent of the pores of the support have a pore volume between about 10 and 100 microns, and a promoting amount of at least one promoter to enhance the efficiency of the catalyst, wherein the amount of silver on the support is sufficient to increase the activity of the catalyst, as determined under STANDARD ETHYLENE OXIDE PROCESS CONDITIONS, by at least about 5°

C., as compared to the same catalyst but containing a lesser amount of silver.

22. The catalyst of claim 21, wherein the activity is increased by at least about 10°

C.

23. The catalyst of claim 21 containing from about 30 to about 60 percent by weight silver.

24. The catalyst of claim 21 containing from about 35 to about 45 percent by weight silver.

25. The catalyst of claim 21, wherein the support has a lamellate morphology.

26. The catalyst of claim 25, wherein the support comprises alpha-alumina.

27. The catalyst of claim 26, wherein the support is at least 98% pure alpha-alumina.

28. The catalyst of claim 21, wherein the support contains a fluorine-containing substance.

29. The catalyst of claim 28, wherein the support has a lamellate morphology.

30. The catalyst of claim 21, wherein the promoter is a cationic promoter.

31. The catalyst of claim 30, wherein the cationic promoter is selected from the group consisting of potassium, rubidium, cesium and mixtures thereof.

32. The catalyst of claim 21, wherein the promoter is an anionic promoter.

33. The catalyst of claim 32 in which the anionic promoter is selected from the group consisting of halides and oxyanions of elements other than oxygen having an atomic number of 7 to 83, inclusive, and being from group 3b through 7b, inclusive, and 3a through 7a, inclusive, of the Periodic Table.

34. The catalyst of claim 33, wherein the anionic promoter is selected from the group consisting of sulfate, fluorosulfate, nitrate, manganate, vanadate, chromate, molybdate, tungstate, rhenate, cerate and mixtures thereof.

35. The catalyst of claim 34 further comprising a cationic promoter comprising at least one of alkali metal and alkaline earth metal.

36. The catalyst of claim 35, wherein the cationic promoter is selected from the group consisting of cesium, rubidium, potassium, and mixtures thereof.