Influence of calcination temperature on structural property of Mn doped γ-Fe₂O₃ catalysts and low-temperature SCR activity

A series of Mn doped γ-Fe₂O₃ catalysts(Fe_0.7Mn_0.3O_z) were prepared with different calcining temperatures via a coprecipitation method, and the influences of calcination temperature on the low-temperature selective catalytic reduction (SCR) activity of Fe_0.7Mn_0.3O_z catalysts were investigated. The catalysts were characterized by N₂ adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The results indicate that Fe_0.7Mn_0.3O_z catalysts calcined at 350 ℃ exhibit the best low-temperature SCR activity, and the NO_x conversion reaches above 90% at 70 ℃ and 100% at 100~200 ℃, while the catalysts calcined at 450 ℃ show a poor low-temperature SCR activity. When the calcination temperature is 350 ℃, the catalysts possess the highest specific surface area and pore volume, flourishing pore structure and appropriate γ-Fe₂O₃ crystallinity. However, when the calcination temperature is increased to 400 or 450 ℃, the sintering takes place and α-Fe₂O₃ appears in Fe_0.7Mn_0.3O_z catalysts, which is unfavorable to the low-temperature SCR reaction. Therefore, 350 ℃ is recommended as the optimum calcination temperature for Fe_0.7Mn_0.3O_z catalysts.