NO_x storage behavior and sulfur-resisting performance of the third-generation NSR catalysts Pt/K/TiO2-ZrO2

摘要

The NO_x storage and reduction(NSR)catalysts Pt/K/TiO2-ZrO2 were prepared by an impregnation method.The techniques of XRD,NH3-TPD,CO2-TPD,H2-TPR and in situ DRIFTS were employed to investigate their NO_x storage behavior and sulfur-resisting performance.It is revealed that the storage capacity and sulfur-resisting ability of these catalysts depend strongly on the calcination temperature of the support.The catalyst with theist support calcined at 500°C,exhibits the largest specific surface area but the lowest storage capacity.With increasing calcination temperature,the NO_x storage capacity of the catalyst improves greatly,but the sulfur-resisting ability of the catalyst decreases.In situ DRIFTS results show that free nitrate species and bulk sulfates are the main storage and sulfation species,respectively,for all the catalysts studied.The CO2-TPD results indicate that the decomposition performance of K2CO3 is largely determined by the surface property of the TiO2-ZrO2 support.The interaction between the surface hydroxyl of the support and K2CO3 promotes the decomposition of K2CO3 to form-OK groups bound to the support,leading to low NO_x storage capacity but high sulfur-resisting ability,while the interaction between the highly dispersed K2CO3 species and Lewis acid sites gives rise to high NO_x storage capacity but decreased sulfur-resisting ability.The optimal calcination temperature of TiO2-ZrO2 support is 650°C.