Heterogeneous catalytic process for alcohol fuels from syngas. Eleventh quarterly technical progress report, July 1994--September 1994

摘要

The principal objectives of this project are to discover and evaluate novel heterogeneous catalysts for conversion of syngas to oxygenates having use as fuel enhancers, to explore novel reactor and process concepts applicable in this process, and to develop the best total process for converting syngas to liquid fuels. We have examined the effect of product recycle (ethanol, n-propanol, isopropanol, carbon dioxide and water) on the performance of 10-DAN-55 (a promoted ZnCr(sub 2)O(sub 4) spinel oxide catalyst) at 40(degrees)C, 1000 psi, GHSV = 12,000 and syngas ratio = 1:2 (alcohol addition) and 1:1 (carbon dioxide and water addition). Ethanol feed is moderately effective for boosting isobutanol activity: the isobutanol rate increases by a modest 19% over the range studied. n-Propanol feed is more effective than ethanol feed, with the rate increasing by a factor of 4, and only a small increase in propane formation up to surface saturation. The methanol rate falls with n-propanol addition and no ethanol is seen, suggesting that there is no back reaction to lighter alcohols from n-propanol. Isopropanol is as effective as ethanol in boosting the isobutanol rate, but a large amount is hydrogenated to propane. Addition of carbon dioxide to the syngas feed adversely affects catalyst performance; the total alcohol rate falls by 44% and the isobutanol rate by 83% on addition of 6% carbon dioxide. An advantage of carbon dioxide addition is that the rate of hydrocarbon formation is suppressed so that the selectivity to total alcohols shows a modest increase from 83% to 89%. The catalyst recovers slowly from the carbon dioxide addition, suggesting some surface species is formed in the presence of carbon dioxide, probably carbonate.