Mechanism of NO reduction by NH3 over CuMnOx catalysts and the influence mechanism of CO

Abstract

A series of CuMnO_x catalysts were prepared through the coprecipitation method to explore the effect of CO participation on the NH₃-SCR reaction. The results showed that the CM-3 sample reached 100% conversion of CO and NO at a temperature lower than 175 °C; this is mainly because the correct proportion of copper and manganese helps to form a solid solution and improve the coordination between metals. Moreover, the interaction principle of CO participating in the NH₃-SCR reaction was thoroughly investigated through in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and density functional theory (DFT). NH₃ has different adsorption modes at different temperatures and competes with CO for the same active center, which significantly affects the catalytic reaction on the surface of the sample. It was confirmed that the deposition of CO₃²⁻ is the main reason for the decline in activity. Finally, the improvement in N₂ selectivity in the reaction with CO participation was due to the produced N₂O not being directly released but being further reduced to N₂ through species such as CO.