Study on Effect of Calcination and Ag Loading on Ag/TiO₂ Catalyst for Low-Temperature Selective Catalytic Oxidation of Ammonia

Herein, Ag/TiO₂ NH₃-SCO catalyst was prepared by impregnation-rotary evaporation method with different calcination temperature and Ag loading content. The results of performance evaluation and characterization showed that the 10 wt% Ag/TiO₂ catalyst calcined at 500 °C showed the best comprehensive performance, with T₉₉ reaching 175 °C and N₂ selectivity reaching 80% at high temperatures. High-temperature calcination will lead to a significant decline in catalyst activity, accompanied by the transformation of TiO₂ from anatase to rutile phase and the obvious change and loss of Ag active sites, which greatly reduces the NH₃ adsorption and redox ability, but it can still maintain a high N₂ selectivity due to unchanged reaction mechanism. In addition, with the increase of Ag loading, excess Ag on Ag/TiO₂ will form metal clusters due to the lack of sufficient anchor points, which helps to improve NH₃-SCO activity. However, excessive Ag loading will reduce the specific surface area and acidic sites, and the Ag species on the catalyst surface will also change to the form of larger particles of Ag₂O, which will lead to the decline of catalytic performance.