Cu/ZnO-based water–gas shift catalysts in shut-down/start-up operation

The water–gas shift performances of Cu/ZnO and Cu/ZnO/Al2O3 catalysts in the challenging shut-down/start-up operation were investigated. The Cu/ZnO catalyst showed comparable activity to the Cu/ZnO/Al2O3 catalyst but better stability in shut-down/start-up cycles, although the latter had much higher Cu surface area and smaller Cu crystallite size. The Cu–ZnO interface sites were thus suggested to participate directly in the reaction. Based on the characterizations, the deactivation of the Cu/ZnO/Al2O3 catalyst was mainly attributed to the loss of active sites due to the formation of carbonate species rather than the sintering of Cu crystallites.