Isobutanol and methanol synthesis on copper catalysts supported on modified magnesium oxide

Alcohols are selectively produced from CO/H-2 on K-CuMgCeOx catalysts, but synthesis rates are strongly inhibited by CO2 formed during reaction. Reaction pathways involve methanol synthesis on Cu, chain growth to C2+ alcohols, and metal-base bifunctional coupling of alcohols to form isobutanol. Ethanol reactions on K-Cu0.5Mg5CeOx show that Cu catalyzes both alcohol dehydrogenation and aldol condensation reactions. CeO2 increases Cu dispersion and MgO surface area and K decreases Cu dispersion, but increases the density of basic sites. Reactions of acetaldehyde and C-13-labeled methanol lead to 1-C-13-propionaldehyde, a precursor to isobutanol. The density and strength of basic sites were measured using a (CO2)-C-12/(CO2)-C-13 isotopic jump method that probes the number and chemical properties of basic sites available at typical isobutanol synthesis temperatures. K or CeO2 addition to CuMgOx increases the density and strength of basic sites and the rates of base-catalyzed ethanol condensation reactions leading to acetone and n-butyraldehyde. The presence of CO in the He carrier during temperature-programmed surface reactions of ethanol preadsorbed on Cu0.5Mg5CeOx decreases the rate of base-catalyzed condensation reactions of preadsorbed ethanol, possibly due to the poisoning of basic and Cu sites by the CO2 formed from CO via water-gas shift reactions. (C) 1997 Academic Press.