Catalytic Cooperation via Spillover of Oxygen: Dehydration—Dehydrogenation of 2-Butanol over SnO2—MoO3 Catalysts

Abstract

Strong synergetic phenomena in the dehydration-dehydrogenation of sec-butyl alcohol were observed at very low temperature using mechanical mixtures of separately prepares SnO2 and MoO3. The principal effects were an increase in conversion as well as increases in yields and selectivities for butene and methyl-ethyl ketone. Characterization of the solids before and after catalytic tests by X-ray Photoelectron Spectroscopy coupled with Transmission Electron Microscopy, Raman Spectroscopy and X-ray Diffraction analysis excluded the possibility of an in situ formation of a mixed oxide or mutual contamination. Attempts for preparing true mixed Sn/Mo oxides have been unsuccessful as predicted from the literature, and catalysts prepared by incipient decomposition of homogenous precursor, which should exhibit maximum contamination, have exhibited much lower activities than the corresponding mechanical mixtures. Taking into account these and previous results with SnO2+Sb2O4 and MoO3+Sb2O4 mixtures, the origen of the observed synergy can be explained by a ''Remote Control Mechanism'': SnO2 acts as a donor of spillover oxygen species (Oso) and MoO3 as an acceptor of Oso. The role of Oso is to create selective sites on MoO3 and to protect them from deactivation.