Selective catalytic oxidation of ammonia to nitrogen on mixed and dual-layer monolithic catalysts

In this paper, the effects of mixed and dual-layer monolithic catalysts on NH3 conversion efficiency and byproduct formation performance were studied under different conditions, in order to find a coating structure with both high activity and high N2 selectivity. The results show that in the absence of NO, the dual-layer structure of Cu-SSZ-13 as the top layer and Ag/Al2O3 as the bottom layer reduces the NH3 conversion efficiency, and the NH3 conversion efficiency further decreases with the increase of the catalyst loading on the top layer, and this trend is further strengthened at higher space velocity. However, the dual-layer catalyst significantly reduces the formation of NOx byproducts. At 600 celcius, NO decreases from 305 ppm in single-layer to 51, 40 and 35 ppm respectively, NO2 and N2O are hardly produced on the dual-layer structure catalyst. In the presence of NO, the dual-layer catalyst is conducive to improving the conversion efficiency of NH3 and NO, and the conversion efficiency of NH3 and NO will be further improved with the increase of Cu-SSZ-13 catalyst loading. In addition, the results of catalytic oxidation performance of mixed structure and dual-layer catalyst under different air conditions show that the mixed structure catalyst has a higher NH3 conversion efficiency than the dual-layer catalyst in the absence of NO, but the by-product generation amount of the mixed structure catalyst is slightly higher than that of the dual-layer catalyst. In the presence of NO, the dual-layer catalyst showed a higher NO conversion efficiency than the mixed catalyst.