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

The characterization and catalytic properties of a new molecular cluster precursor, Ti4O4[OCH(CH3)(2)](4){(CO)(9)Co3CCO2}(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 degrees C) as compared to M-2{(CO)(9)Co3CCO2}(4) (where M=Co, Cu, or Mo) and M4O{(CO)(9)Co3CCO2}(6) (where M = Zn or Co), which are stable only to 300 degrees C. It has been found that the HT1-Ti4Co12 structure provides significantly better 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. (C) 1998 Academic Press.