Selective hydrogenation of 2-butenal using cluster of clusters-based catalysts

Complex cobalt-carbonyl ligand clusters of clusters are used as well defined molecular precursors for self-supported single metal or bimetallic catalysts. These precursors incorporate two metals: an outer layer formed from the complex cobalt cluster carbonyl ligands [(CO)(9)Co3CCO2] and an inner core of the metal carboxylate cores. Two types of precursor structures are used: one with two metal atoms in the core (designated as M(2)Co(12), where M = Co, Cu, and Mo) and the other with four metal atoms in the core bonded to a centering oxygen atom (designated as M(4)Co(18), where M = Co and Zn). The catalysts are prepared in situ by partial thermolysis (LT catalysts) or complete thermolysis (HT catalysts) of the cluster of clusters precursors. The catalysts derived from Co4Co18, Zn4Co18, Co2Co12, Mo2Co12, and Cu2Co12 precursors are used in the selective hydrogenation reaction of 2-butenal. The desired product of the reaction is the thermodynamically less favored unsaturated alcohol (2-butenol). The highest 2-butenol selectivity observed was 100% over HT-Co2Co12 catalyst at 373 K. The highest 2-butenol yield observed in our experiments was approximate to 28% using HT-Co4Co18 at 423 K. The activity and selectivity behavior of HT-Co4Co18 was stable over at least 50 h of operation. The factors affecting 2-butenol selectivity and yield during 2-butenal hydrogenation using these catalysts are discussed. (C) 1996 Academic Press, Inc.