Self-coupling of secondary alcohols by Ni/CeO2 catalyst

Abstract

Supported nickel catalysts are studied for the liquid phase CC self-coupling of aliphatic secondary alcohols under additive free conditions in N2 atmosphere. Among various Ni catalysts, 1 or 3wt% Ni/CeO2 catalysts pre-reduced in H2 shows highest yield (94%) of a dimer product (a higher ketone) for the self-coupling of 1-octanol at 130°C, and the catalyst is reused. The catalysts are also effective for self-coupling of various secondary alcohols, providing the first heterogeneous catalytic system for the self-coupling of secondary alcohols under mild conditions. Effects of support material and oxidation state of Ni on the activity are studied and it is found that both CeO2 and metallic Ni are indispensable for the reaction. A possible reaction mechanism is proposed, in which ketones, formed by dehydrogenation of alcohol, undergone Aldol condensation to give α,β-unsaturated ketone which is finally hydrogenated by in situ formed NiH species.