Role of promoters and catalyst supports for selective synthesis of higher alcohols over molybdenum carbides

The synthesis of higher alcohols from syngas is a very promising avenue as syngas can be derived from renewable (biomass) and non-renewable feedstock (coal, natural gas). To date no commercial process exists for the conversion of syngas into higher alcohols due to poor alcohols yield and selectivity. The search for selective catalysts requires fundamental insight into how to enhance active sites for the formation of alcohols. In the present work, the dispersion of K2CO3 promoted molybdenum carbides over three different supports i.e., highly acidic (gamma-alumina), neutral (activated carbon), and basic (magnesium oxide) has been studied. The results revealed that acid sites of gamma-alumina expedited the dispersion of the K2CO3 promoter over the molybdenum carbide catalyst and facilitated carbon monoxide dissociation to form C2+ alcohols. The effect of the incorporation of cobalt into the textural and catalytic properties of alumina supported K-Mo2C was also investigated. The elemental mapping of Co into the K-Mo2C structure showed the presence of segregated Co and Mo2C islands, but an interaction was observed at the molecular level, resulting in a different H-2 temperature-programmed desorption pattern. With the decreased availability of surface adsorbed hydrogen of the Co promoted K-Mo2C/Al2O3, the concentration of methanol was significantly reduced and the product selectivity shifted more towards higher alcohols.