Mixed Oxide Supports Reduce Methanol Selectivity in the Catalytic Synthesis of Higher Alcohols From Syngas Over Potassium-Promoted Molybdenum Sulfide Catalysts

Molybdenum sulfide, a well-known hydrodesulfurization catalyst, is being increasingly investigated as a catalyst for conversion of synthesis gas to higher alcohols. Here it is demonstrated that with a 5% Mo loading, potassium promoted molybdenum sulfide catalysts supported on basic, mixed metal oxides derived from decomposed, synthetic hydrotalcites can convert syngas into higher alcohols with reduced methanol and increased n-propanol selectivity relative to bulk molybdenum sulfide. Reactions are carried out at 310 ºC and 1500 psig in a differential, downflow, fixed bed reactor.  When Mo loading is increased to 15% loading, catalyst performance increasingly resembles that of bulk molybdenum sulfide at carbon monoxide conversions characteristic of a differential reactor (<8%). XANES and Raman spectroscopy reveal chemically similar Mo domains while XRD and HRTEM show the domains to differ in size. Catalytic differences may be associated with the ability of the basic support to couple alcohols when the support:Mo ratio is adequately high, producing an atypical Anderson-Schultz-Flory distribution among the products.