Identification of the Active Sites in the Dehydrogenation of Methanol on Pt/Al2O3 Catalysts

Conversion of oxygenates derived from biomass is a promising strategy for the production of fuels and chemicals. The needed H-2 can be supplied simultaneously (and sustainably) via aqueous phase reforming (APR; CnH2nOn + nH(2)O -> nCO(2) + 2nH(2)). APR is typically carried out over supported metal catalysts under liquid water. Dehydrogenation is the first constituent reaction in APR and involves both C-H and O-H bond cleavages; however, details about the mechanism and natures of the active sites remain unknown. Herein, such details are provided for methanol dehydrogenation over a supported Pt/Al2O3 catalyst. Using density functional theory calculations, we find that methanol dehydrogenation occurs on the Pt terraces and at the Pt/Al2O3 interfaces but follows different paths: on interfacial sites, O-H cleavage occurs first and dehydrogenation follows a methoxy route, whereas on terrace sites, C-H cleavage occurs first and dehydrogenation follows a hydroxymethyl route.