Mc. Laneve et al., TITANIUM-COBALT CLUSTER OF CLUSTER-BASED CATALYSTS FOR THE SELECTIVE HYDROGENATION OF ALPHA,BETA-UNSATURATED ALDEHYDES, Journal of catalysis (Print), 177(1), 1998, pp. 11-21
The characterization and catalytic properties of a new molecular clust
er precursor, Ti4O4[OCH(CH3)(2)](4){(CO)(9)Co3CCO2}(4), denoted Ti4Co1
2, were studied during the vapor phase hydrogenation of 2-butenal to f
orm the thermodynamically less favored product, 2-butenol. Pyrolysis o
f 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 stab
le only to 300 degrees C. It has been found that the HT1-Ti4Co12 struc
ture provides significantly better selectivity to 2-butenol than the H
T2-Ti4Co12 structure. In-situ DRIFTS measurements during the decomposi
tion 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 specu
late that these ions are related to the high selectivity of these mate
rials. (C) 1998 Academic Press.