载体不同焙烧温度对NSR催化剂Pt-K2CO3/K2Ti8O17中碳酸盐的状态和储存性能的影响

series of carbonate based NOx storage and reduction catalysts Pt-K2CO3/K2Ti8O17 with the support calcined at different temperatures were synthesized by sequential impregnation. The results of NOx storage and reduction show that the catalytic activity of these catalysts depends strongly on the calcination temperature of support. The catalyst with its support calcined at 350℃ possesses the largest BET specific surface area (211 m2/g), the highest NOx storage capacity (0.68 mmol/g) and the highest NOx reduction percentage (99.1%). The utilization efficiency of K species in this catalyst is as high as 94.4%. Based upon multiple characterizations, such as XRD, SEM, NH3-TPD and CO2-TPD, it is found that the calcination over 650℃ can cause the decomposition of K2Ti8O17 to K2Ti6O13 and TiO2, making the specific surface areas, morphology, acid-base properties of the support and the distribution of K species obviously different, which further influences the NOx storage capacity. It is also revealed that the K species exist in several forms including K2O, -OK groups, surface potassium carbonate and bulk or bulk-like potassium carbonate, which have different stability. The relative concentrations of these species vary with support calcination temperature, among them the surface carbonate species are identified as the most favorable species to NOx storage. In-situ DRIFTS results indicate that monodentate nitrates and monodentate nitrites are the dominant NOx storage species.