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.