A comparative study of the deactivation mechanisms of the Au/CeO _2 catalyst for water-gas shift under steady-state and shutdown/start-up conditions in realistic reformate

摘要

The deactivation mechanisms of the Au/CeO_2 catalyst in steady-state and shutdown/start-up WGS reactions were investigated in realistic reformate at 250°C. Catalyst deactivation due to sintering was excluded. After steady-state operation, the original activity was not recovered by removing the deposited carbonate species. The influences of the component gases of realistic reformate on the activity suggest that loss of the Au-CeO _2 interaction caused by the reducing H_2 and CO is the main reason for catalyst deactivation. Under the shutdown/start-up condition, the catalyst suffered more drastic deactivation, although it underwent a lesser degree of reduction. A good correlation between the extent of deactivation and the amount of the carbonate species indicates that catalyst deactivation is mainly caused by enhanced formation of the carbonate species, especially through a combined effect of CO_2 and H_2O, during the low-temperature shutdown and start-up steps. The implications of these findings for improved applications of the Au/CeO_2 catalyst in WGS are indicated.