Hydrogen production by methanol reforming: post-reaction characterisation of a Cu/ZnO/Al2O3 catalyst by XPS and TPD

Post-reaction X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) experiments have been carried out after exposure of a commercial Cu/ZnO/Al2O3 catalyst to methanol reforming conditions in the presence of O2 and H2O. A dependence of the copper oxidation state on the temperature was observed, with low temperatures favouring a higher oxidation state. In the presence of water, Cu(II) was formed at T≤485 K, giving rise to a very low catalytic activity. Under methanol dry partial oxidation conditions at T≥530 K a decrease of the Cu surface concentration was observed. Adsorbed methoxy species were found on the surface after all catalytic treatments, with the amount decreased by the presence of water in the feed. The presence of O2 favoured the formation of surface formate.