The decomposition of Mn-substituted siderite during coaling enhanced the transformation of NO before catalyst bed: Effect of Mn substitution

Abstract The substitution of Mn for Fe in the structure of siderite, a common mineral in coal, is universal. The effects of Mn on the transformation of siderite during coaling and the de-NO performance of the transformed products in flue gas pipelines after injecting NH3 were investigated, and a kinetic study was also performed. The results showed that the Mn-substituted siderite ((Mn, Fe)CO3) was transformed into Mn-substituted hematite ((Mn, Fe)2O3). The Fe2O3 derived from siderite displayed a positive effect on NO conversion. The substitution of Mn considerably improved the de-NO performance at reaction temperatures of 100–200 °C, especially for the 12% Mn substitution amounts (increased by 81.9–51.4%). A larger surface area, more chemisorbed oxygen and acid sites, and outstanding redox capacity are responsible for this phenomenon. Furthermore, both the Eley-Rideal and Langmuir-Hinshelwood mechanism take part in the de-NO process by selective catalytic reduction in the presence of NH3 (NH3-SCR), and the catalytic oxidization (CO) reaction occurred above 200 °C according to the in situ DRIFTS and kinetic study results, respectively. This study benefits the comprehension of NO behavior and the de-NO mechanism in flue gas pipelines after injecting NH3 during coaling.