Cobalt-molybdenum sulfide catalyst materials and methods for stable alcohol production from syngas
The present invention provides methods and compositions for the chemical conversion of syngas to alcohols. The invention includes catalyst compositions, methods of making the catalysts, and methods of using the catalysts including techniques to maintain catalyst stability. Certain embodiments teach compositions for catalyzing the conversion of syngas into products comprising at least one C 1 -C 4 alcohol, such as ethanol. These compositions generally include cobalt, molybdenum, and sulfur, and avoid metal carbides both initially and during reactor operation.
1. A method of accelerated aging of a sulfide catalyst for the conversion of syngas to alcohols, said method comprising:
(a) providing a test reactor including a test catalyst containing sulfur;
(b) flowing syngas into said test reactor at conditions effective to produce an alcohol; and
(c) injecting a suitable aging accelerant into said test reactor, wherein said aging accelerant is capable of causing sulfur loss from said test catalyst at a rate that is faster than the rate in the absence of said aging accelerant, wherein said aging accelerant comprises methanol.
2. The method of claim 1 , wherein said methanol is injected in step (c) at about the equilibrium amount in accordance with a methanol/syngas reaction equilibrium produced under said conditions in step (b).
3. The method of claim 1 , wherein said method is conducted for a test time selected from about 1 hour to about 200 hours.
4. The method of claim 3 , wherein said test time is selected from about 10 hours to about 100 hours.
5. The method of claim 1 , comprising an acceleration factor of at least 5, wherein said acceleration factor is the rate of sulfur loss from said test catalyst in the presence of said aging accelerant divided by the rate of sulfur loss in the absence of said aging accelerant.
6. The method of claim 5 , wherein said acceleration factor is at least 10.
7. The method of claim 6 , wherein said acceleration factor is at least 20.
8. The method of claim 1 , further comprising measuring at least one parameter of interest at a plurality of times during operation of said test reactor, to generate a test response.
9. The method of claim 8 , wherein said at least one parameter of interest is selected from the group consisting of CO conversion, ethanol selectivity, total alcohol selectivity, total alcohol productivity, methane selectivity, and sulfur concentration exiting said test reactor.
10. The method of claim 9 , wherein said test response includes at least one correlation selected from the group consisting of decreasing CO conversion, decreasing ethanol selectivity, decreasing total alcohol selectivity, decreasing total alcohol productivity, increasing methane selectivity, and increasing sulfur concentration exiting said test reactor.
11. The method of claim 10 , further comprising characterizing said test catalyst by predicting the lifetime or stability of a commercial catalyst with substantially the same composition as said test catalyst.
12. A method of characterizing a plurality of sulfide catalysts, wherein each catalyst composition is a distinct catalyst that is independently subjected to the following steps:
(a) providing a test reactor suitable for evaluating each of the sulfided catalysts;
(b) flowing syngas into the test reactor at conditions effective to produce an alcohol, for each of the sulfided catalysts; and
(c) injecting a suitable aging accelerant into the test reactor, for each of the sulfided catalysts, wherein the aging accelerant is capable of causing sulfur loss from each of the sulfided catalysts at a rate that is faster than the rate in the absence of the aging accelerant,
wherein said aging accelerant comprises methanol.
13. A method of characterizing performance of a sulfide catalyst for the conversion of syngas to alcohols under a plurality of process conditions, the method comprising:
(a) providing a test reactor suitable for evaluating the sulfided catalyst;
(b) flowing syngas into the test reactor at conditions effective to produce an alcohol, for each of the plurality of process conditions; and
(c) injecting a suitable aging accelerant into the test reactor, for each of the plurality of process conditions, wherein the aging accelerant is capable of causing sulfur loss from each of the sulfided catalysts at a rate that is faster than the rate in the absence of the aging accelerant,
wherein said aging accelerant comprises methanol.