Methods of making improved cobalt-molybdenum-sulfide catalyst compositions for higher alcohol synthesis
This invention improves prior methods of making cobalt-molybdenum-sulfide catalysts for alcohol production from syngas. In one aspect, improved methods are provided for making preferred cobalt-molybdenum-sulfide compositions. In another aspect, processes utilizing these catalysts for producing at least one C 1 -C 4 alcohol, such as ethanol, from syngas are described.
1. A method for making a cobalt-molybdenum-sulfide composition, said method comprising the steps of:
(i) dissolving ammonium dimolybdate, [NH 4 ] 2 [Mo 2 O 7 ], in aqueous ammonia, thereby producing a molybdate solution;
(ii) combining hydrogen sulfide with at least some of said molybdate solution, thereby producing a tetrathiomolybdate solution comprising [MoS 4 ] 2− ;
(iii) combining a Co(II) solution with at least some of said tetrathiomolybdate solution to form a first precipitate within a suspension;
(iv) combining sulfuric acid with at least some of said suspension, to form a second precipitate;
(v) filtering said second precipitate, wherein said filtering removes a portion of water present in said second precipitate, thereby creating a filter cake; and
(vi) thermally processing said filter cake to produce a calcined material comprising cobalt, molybdenum, and sulfur,
wherein step (vi) includes drying said filter cake in a substantially inert environment to produce a dried material and calcining said dried material to produce said calcined material.
2. The method of claim 1 , wherein in step (i), the ratio of moles of ammonia contained in said aqueous ammonia divided by moles of molybdenum contained in said ammonium dimolybdate is selected from about 1.2 to about 2.
3. The method of claim 2 , wherein said ratio is selected from about 1.5 to about 1.8.
4. The method of claim 1 , wherein step (ii) includes a stoichiometric excess of said hydrogen sulfide to produce said [MoS 4 ] 2− .
5. The method of claim 1 , wherein said tetrathiomolybdate solution in step (ii) or step (iii) is supersaturated.
6. The method of claim 1 , wherein said tetrathiomolybdate solution further includes a non-zero amount of [MoOS 3 ] 2− .
7. The method of claim 6 , wherein the [MoS 4 ] 2− /[MoOS 3 ] 2− ratio in said tetrathiomolybdate solution is between about 5 and about 100.
8. The method of claim 1 , wherein said Co(II) solution in step (iii) is a cobalt acetate solution.
9. The method of claim 1 , wherein said Co(II) solution in step (iii) is a cobalt sulfate solution.
10. The method of claim 1 , wherein step (v) includes filtering in the presence of air.
11. The method of claim 1 , wherein step (v) includes filtering in the presence of a substantially inert environment.
12. The method of claim 1 , further comprising washing said filter cake after step (v) with water.
13. The method of claim 12 , wherein said washing removes at least 99% of sulfates present prior to said washing.
14. The method of claim 1 , wherein said filter cake is not dried between steps (v) and (vi).
15. The method of claim 1 , wherein step (vi) includes calcining said dried material in a substantially inert environment.
16. The method of claim 1 , further comprising cooling said calcined material in a substantially inert environment.
17. The method of claim 1 , wherein step (vi) is carried out immediately after step (v).
18. The method of claim 1 , further comprising combining said calcined material with a base promoter selected from the alkali or alkaline earth series, thereby producing a base-promoted catalyst.
19. The method of claim 18 , wherein said base promoter is selected from the group consisting of potassium hydroxide, potassium carbonate, potassium oxalate, and potassium acetate.
20. The method of claim 18 , wherein said base promoter is introduced to said filter cake prior to step (vi).
21. The method of claim 20 , wherein said base promoter is added in solid form to said filter cake and then said filter cake with said base promoter are collectively subjected to step (vi).
22. A method for making a cobalt-molybdenum-sulfide composition, said method comprising the steps of:
(i) dissolving ammonium dimolybdate, [NH 4 ] 2 [Mo 2 O 7 ], in aqueous ammonia, thereby producing a molybdate solution;
(ii) combining hydrogen sulfide with at least some of said molybdate solution, thereby producing a tetrathiomolybdate solution comprising [MoS 4 ] 2− ;
(iii) combining a Co(II) solution with at least some of said tetrathiomolybdate solution to form a first precipitate within a suspension;
(iv) combining sulfuric acid with at least some of said suspension, to form a second precipitate;
(v) filtering said second precipitate, wherein said filtering removes a portion of water present in said second precipitate, thereby creating a filter cake; and
(vi) thermally processing said filter cake to produce a calcined material comprising cobalt, molybdenum, and sulfur,
wherein step (vi) includes drying at a drying temperature selected from about 80-200° C. and calcining at a calcination temperature selected from about 350-650° C.
23. The method of claim 22 , wherein said drying temperature is selected from about 100-150° C.
24. The method of claim 22 , wherein said calcination temperature is selected from about 450-550° C.
25. The method of claim 22 , wherein said calcining is conducted for a calcination time selected from about 10 minutes to about 4 hours.
26. The method of claim 25 , wherein said calcination time is selected from about 1 to 2 hours.
27. The method of claim 22 , wherein said drying and calcining are carried out in the same apparatus.
28. The method of claim 22 , wherein step (vi) further includes dwelling at an intermediate temperature higher than said drying temperature and lower than said calcination temperature, wherein said dwelling is conducted for a dwell time from about 1-24 hours.
29. The method of claim 28 , wherein said intermediate temperature is selected from about 120-350° C.
30. The method of claim 29 , wherein said intermediate temperature is selected from about 200-300° C.
31. The method of claim 28 , wherein said dwell time is selected from about 2-16 hours.
32. The method of claim 31 , wherein said dwell time is selected from about 4-8 hours.
33. A method of producing at least one C 1 -C 4 alcohol, said method comprising:
(i) dissolving ammonium dimolybdate, [NH 4 ] 2 [Mo 2 O 7 ], in aqueous ammonia, thereby producing a molybdate solution;
(ii) combining hydrogen sulfide with at least some of said molybdate solution, thereby producing a tetrathiomolybdate solution comprising [MoS 4 ] 2− ;
(iii) combining a Co(II) solution with at least some of said tetrathiomolybdate solution to form a first precipitate within a suspension;
(iv) combining sulfuric acid with at least some of said suspension, to form a second precipitate;
(v) filtering said second precipitate, wherein said filtering removes a portion of water present in said second precipitate, thereby creating a filter cake;
(vi) thermally processing said filter cake to produce a calcined material comprising cobalt, molybdenum, and sulfur;
(vii) combining said calcined material with a base promoter selected from the alkali or alkaline earth series, thereby producing a base-promoted catalyst; and
(viii) reacting syngas over said base-promoted catalyst to produce at least one C 1 -C 4 alcohol.
34. The method of claim 33 , wherein said at least one C 1 -C 4 alcohol is ethanol.
35. The method of claim 33 , further comprising co-feeding methanol in an amount in equilibrium with said syngas.
36. The method of claim 33 , further comprising co-feeding methanol at less than an amount in equilibrium with said syngas.
37. The method of claim 33 , wherein step (vi) includes drying said filter cake in a substantially inert environment to produce a dried material, and then calcining said dried material to produce said calcined material.
38. The method of claim 33 , wherein step (vi) includes drying at a drying temperature selected from about 80-200° C. and calcining at a calcination temperature selected from about 350-650° C.