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

Abstract

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 K 2 CO 3 promoted molybdenum carbides over three different supports i.e., highly acidic (ɣ-alumina), neutral (activated carbon), and basic (magnesium oxide) has been studied. The results revealed that acid sites of ɣ-alumina expedited the dispersion of the K 2 CO 3 promoter over the molybdenum carbide catalyst and facilitated carbon monoxide dissociation to form C 2þ alcohols. The effect of the incorporation of cobalt into the textural and catalytic properties of alumina supported K-Mo 2 C was also investigated. The elemental mapping of Co into the K-Mo 2 C structure showed the presence of segregated Co and Mo 2 C 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-Mo 2 C/Al 2 O 3 , the concentration of methanol was significantly reduced and the product selectivity shifted more towards higher alcohols.