Selective oxidation and dehydrogenation of benzyl alcohol on ABB′O3 (A=Ba, B=Pb, Ce, Ti and B′=Bi, Cu, Sb)-type perovskite oxides-temperature programmed reduction studies

Selective oxidation and dehydrogenation of benzyl alcohol have been carried out on ABB'O-3 (A=Ba, B=Pb, Ce, Ti and B'=Bi, Cu, Sb)-type perovskite oxides in the absence and in the presence of oxygen. Partial reduction of the catalyst is observed when the reaction is carried out in the absence of oxygen or at low partial pressures of oxygen. Reduced catalysts were characterised by XRD. Temperature-programmed reduction studies were carried out to determine the reducibility of the catalyst. Catalytic activity is found to depend on the reducibility of the catalysts. Copper-containing perovskites are highly reducible and BaTiO3 and BaCeO3 are the least reducible. Catalytic activity and reducibility are correlated with the metal-oxygen bonding as well as free energy of reduction of B site cations. A mechanism is proposed, which explains the ratio of benzaldehyde to toluene based on the reducibility. (C) 1998 Elsevier Science B.V. All rights reserved.