Striking Improvement of N<sub>2</sub> Selectivity in NH<sub>3</sub> Oxidation Reaction on Fe<sub>2</sub>O<sub>3</sub>-Based Catalysts via SiO<sub>2</sub> Doping
Xiaoyu Ji, Bifeng Zhang, Huaizhu Wang, Yandi Cai, Qinglong Liu, Kaiqiang Wu, Da‐Wei Li, Wei Tan, Fudong Liu, Lin Dong
Abstract
The emission of NH 3 has been reported to pose a serious threat to both human health and the environment. To efficiently eliminate NH 3, catalysts for the selective catalytic oxidation of NH 3 (NH 3 –SCO) have been intensively studied. Fe 2 O 3 -based catalysts were found to exhibit superior NH 3 oxidation activity; however, the low N 2 selectivity made it less attractive in practical applications. In this work, aimed at improving the N 2 selectivity on Fe 2 O 3 -based catalysts, a simple SiO 2 doping strategy was proposed. Although the NH 3 oxidation activity showed almost no change on Fe 2 O 3 after SiO 2 doping, the N 2 selectivity was significantly improved. Systematic characterizations revealed that SiO 2 doping could increase the specific surface area of Fe 2 O 3, and a strong interaction of Fe–O–Si was formed in Fe 2 O 3 –SiO 2 mixed oxide catalysts. Furthermore, abundant Brønsted acid sites were formed on Fe 2 O 3 –SiO 2 catalysts due to the facile hydrolysis of the Fe–O–Si structure into Si–OH and Fe–OH. Although SiO 2 doping was found to weaken the redox ability of Fe 2 O 3, the abundant Brønsted acid sites on Fe 2 O 3 –SiO 2 catalysts could facilitate NH 3 oxidation reaction through an internal SCR ( i -SCR) pathway, thus achieving superior N 2 selectivity. This work can provide new insights into constructing efficient NH 3 –SCO catalysts with high N 2 selectivity.