Low-Temperature NH3-SCR Performance and In Situ DRIFTS Study on Zeolite X-Supported Different Crystal Phases of MnO2 Catalysts

In this study, a series of zeolite-X-supported different crystal phases MnO2 (α-MnO2, β-MnO2, γ-MnO2, and σ-MnO2) catalysts were prepared via solid-state diffusion method high-heat treatment to explore their low-temperature NH3-SCR performance. All the featured typical octahedral zeolite X structures manganese dioxides species various types dispersed across support surface. Throughout entire temperature range reaction, γ-MnO2/X catalyst had highest NO conversion. Additionally, β-MnO2/X, γ-MnO2/X, σ-MnO2/X nearly 100% N2 selectivity, whereas α-MnO2/X lowest selectivity (about 90%) below 125 °C. Moreover, demonstrated superior acidity capacity reduction ability compared with other three catalysts. contained essential intermediates NH2NO NH4NO3 species, which are SCR reaction. More acid sites nitrate existed on than catalysts, thereby boosting