Ethanol condensation to butanol and higher alcohols over nickel and cobalt decorated CeO2-Al2O3 mixed oxide catalysts

A new series of bimetallic Ni-Co catalysts, prepared by step wise substitution of Ni by Co, in mono metallic Ni (8%)/ CeO2 -Al2O3, with the compositions of 6%Ni-2% Co, 4%Ni-4%Co, 2.5%Ni-5.5%Co and 8%Co, have been evaluated for conversion of ethanol to butanol and higher alcohols according to Guerbet alcohol chemistry. XRD, TPR and XPS studies reveal the formation of Ni-Co alloys at specific bimetallic compositions. Maximum reducibility is observed for the composition 4%Ni-4%Co, which also displays maximum ethanol conversion (55.1%) with C4+ alcohols selectivity of 50.2%, which are higher than those realized for mono metallic Ni and Co catalysts. Ni-Co alloys in bimetallic catalysts promote the crucial ethanol dehydrogenation and C-4 and C4+ aldehydes hydrogenation steps in the Guerbet process, thereby increasing ethanol conversion and C4+ alcohol selectivity. Selection of bimetallic catalysts with optimum compositions seems to be one of strategies to improve ethanol conversion and selectivity for higher alcohols.