Heterogeneous cobalt catalysts for the acceptorless dehydrogenation of alcohols

Abstract

A series of transition metal(M)-loaded TiO₂ catalysts (M/TiO₂) and Co-loaded catalysts on various support materials were prepared by an impregnation method, followed by in situ H₂-reduction at 400 °C, and tested for the acceptor-free oxidation of cyclododecanol in the liquid phase. Among the catalysts including noble metal catalysts, Co/TiO₂ showed the highest activity. In the presence of Co/TiO₂ (0.1–3 mol%) the dehydrogenation of various aliphatic secondary alcohols proceeded to afford the corresponding ketones. The catalyst was recoverable and was reused after the H₂-reduction treatment. Based on the spectroscopic characterization of the catalyst combined with the studies on the effect of the Co oxidation states on the catalytic activity, it is clarified that the surface metallic Co sites with electron deficiency are the catalytically active species.