On the nature of surface structural changes in Cu ZnO methanol synthesis catalysts

Infrared spectroscopic studies of CO adsorption have been used to elucidate the surface structure of Cu/ZnO methanol synthesis catalysts. Significant frequency shifts are observed as functions of the severity of the reduction treatment. The changes, which are unlike those observed in other supported Cu catalysts, cannot be interpreted solely by changes in morphology and abundance of different Cu surface planes. Rather, the band shifts are suggested to be related to the formation of Cu-Zn surface alloys under more severe reduction conditions. The formation/destruction of the surface alloys is apparently reversible and it is proposed that such processes may be the origin of many of the unusual steady state and transient kinetic behaviors observed for Cu/ZnO catalysts.