Improved NH_3-SCR deNO_x activity and tolerance to H_2O & SO_2 at low temperature over the Nb_mCu_(0.1-m)Ce_(0.9)O_x catalysts: Role of acidity by niobium doping

摘要

A series of NbmCu0.1-mCe0.9Ox catalysts were synthesized with the help of citric acid method, and used for the selective catalytic reduction of NOx with NH3 (NH3-SCR). The catalytic performance of the NbmCu0.1-mCe0.9Ox samples was greatly improved after the introducing of niobium. Among all catalysts, the Nb0.06Cu0.04Ce0.9Ox catalyst revealed the best low-temperature SCR activity, higher N2 selectivity and extraordinary SO2 and H2O durability with 100% NO conversion at 150-390 degrees C. The various characterization techniques were carried out to investigate the effect of niobium doping on the physical structures, surface properties and NH3-SCR activity of catalysts. Results reveal that the oxidation ability decrease but the acidity is enhanced with the Nb addition. The improved acidity by niobium doping is considered the primary cause for the superior deNOx performance of the Nb0.06Cu0.04Ce0.9Ox catalyst at low temperature, which can offset the negative effects of the reduced oxidation ability on activity. Furthermore, in situ DRIFTS results were applied for the investigation of the reaction process in detail.