Titanium-cobalt cluster of cluster-based catalysts for the selective hydrogenation of α,β-unsaturated aldehydes

Abstract

The characterization and catalytic properties of a new molecular cluster precursor, Ti404[OCH(CH3)2] 4{(CO)9Co3CCO2}4, denoted Ti4Co12, were studied during the vapor phase hydrogenation of 2-butenal to form the thermodynamically less favored product, 2-butenol. Pyrolysis of this precursor yields three active catalytic forms, designated LT-, HT1-, and HT2-. This catalyst shows enhanced thermal stability (up to 400°C) as compared to M2{(CO)9Co3 CCO2}4 (where M = Co, Cu, or Mo) and M4O{(CO)9Co3CCO2}6 (where M = Zn or Co), which are stable only to 300°C. It has been found that the HT1-Ti4Co12 structure provides significantly bet-ter selectivity to 2-butenol than the HT2-Ti4Co12 structure. In-situ DRIFTS measurements during the decomposition of the precursor indicate the presence of COO- groups during the formation of the selective HT1-Ti4Co12 form. These groups disappear at higher temperatures when the HT2-Ti4Co12 catalyst is formed. We speculate that these ions are related to the high selectivity of these materials. © 1998 Academic Press.