Comparative study on N2O formation pathways over bulk MoO3 and MoO3-x nanosheets decorated Fe2O3-containing solid waste NH3-SCR catalysts

Abstract

NH3-SCR technology with commercialized V2O5-WO3(MoO3)/TiO2 catalysts has become the most efficient technology for the removal of NOx from coal-fired power plants. However, the weaknesses of V2O5-WO3(MoO3)/TiO2 catalysts such as the biotoxicity of vanadium species and high cost restrict their increased applicability. Fe2O3-based NH3-SCR catalysts show potential in placing traditional catalysts due to their good N2 selectivity, excellent environmentally friendly performance, high thermal stability, and low cost. In this work, low cost Fe2O3-containing solid waste was exploited as the base material for NH3-SCR catalyst preparing. Moreover, bulk MoO3 and MoO3-x nanosheets decorated Fe2O3 composite NH3-SCR catalysts were synthesized and both revealed conspicuously improved NOx removal efficiency compared with bare-Fe2O3 catalyst. However, the N2 selectivity of these two catalysts showed significant differences. Therefore, comprehensive characterizations, NH3 oxidation experiments, and in-situ diffusion Fourier transform infrared spectroscopy (DRIFTS) experiments were performed to determine the N2O formation pathways of the above two catalysts. The redox properties were highly related to the N2O generated from NH3 oxidation. Moreover, the huge difference in NH3 and NO adsorption ability led to disparate reaction mechanisms over the two catalysts. This new understanding of the N2O formation mechanism has the potential to guide the rational design of improved NH3-SCR catalysts suffering from low N2 selectivity.