Time-Resolved XANES Investigation of CuO/ZnO in the Oxidative Methanol Reforming Reaction

CuO/ZnO catalysts were examined by time-resolved X-ray absorption spectroscopy during oxidative reforming of methanol. Under low oxygen conversion conditions, Cu2+ was the dominant copper species and combustion of methanol to carbon dioxide and water was the primary reaction. After complete oxygen conversion, Cu2+ was reduced to Cu0 while the principal activity of the catalyst shifted to steam reforming, where the dominant product was hydrogen. Cu+ was observed as a transient species in the reduction of Cu2+ to Cu0 and no activity was attributed to it. Increasing the oxygen partial pressure increased the rate of reduction of Cu2+. This observation was attributed to a heating effect associated with an enhancement of the combustion rate. Additional experiments showed that the catalyst could recover its original activity after a reduction/oxidation cycle.