Study on N2 selectivity of iron-manganese ore catalysts in NH3-SCR process

Natural iron-manganese ores exhibit a good deNO(x) activity at low temperatures after a simple treatment, but the reason for its low N-2 selectivity requires further in-depth study. This work conducted deNO(x) performance and characterization tests on iron-manganese ore catalysts. Based on the experimental results, a simplified computational model of the iron-manganese ore catalyst (Fe2O3/MnO2 (110) surface) was constructed, and the density functional theory (DFT) method was used to investigate the mechanism of N-2 formation in the NH3-SCR process. Fe and Mn in the iron-manganese ore play an important role in the deNO(x) activity, and NH3 forms the stable chemical adsorption on its surface, especially on the Fe site, where the adsorption capacity of NH3 is stronger than that of Mn site. The Fe site exhibits better ability than the Mn site in the dehydrogenation reaction of NH3. However, in a comprehensive comparison, the capability of iron-manganese ore catalyst to promote NH3 dehydrogenation is not high. In addition, the key NH2NO intermediate prefers to form on the Mn site over the Fe2O3/MnO2 (110) surface. Among them, the Mn site is better than the Fe site in promoting the decomposition of NH2NO intermediate to form N-2. The study can further understand the microscopic mechanism of iron-manganese ore catalysts in N-2 formation, which lays a foundation for improving the N-2 selectivity of iron-manganese ore deNO(x) catalysts.