Low-Temperature Selective Catalytic Reduction of NO with NH_3 over a Biochar-Supported Perovskite Oxide Catalyst

摘要

Maintaining high denitration efficiency for the selective catalytic reduction with ammonia (NH_3-SCR) at low temperatures is challenging. In this work, a modified biochar-supported perovskite oxide catalyst was synthesized and implemented to NO conversion in the low-temperature range of 100-250 ℃. Different modification methods were compared, where the combination of nitric acid and air oxidation treatment endowed biochar with abundant acidic surface oxygen-containing groups and a higher specific surface area as a support. The perovskite oxide (LaMnO_3) and the LaMnO_3/biochar catalysts were prepared to investigate the interactions between the catalyst and the support. The LaMnO_3/biochar catalyst exhibited excellent denitration efficiency and good N_2 selectivity, achieving over 80 NO conversion within the entire temperature range of 100-250 ℃ (S_N_2 > 90), and the highest NO conversion reached 95.8 at 225 ℃ (S_N_2 = 95.4). This catalyst provided synergistic adsorption capacity for NH3 as a result of the acidic function of perovskite oxide and acidic oxygen-containing functional groups of the modified biochar support. Additionally, LaMnO_3 showed an eminent redox capability for NO conversion due to the high content of Mn~(4+) and chemically adsorbed oxygen species. Finally, NH_3-SCR reaction mechanisms were proposed on the basis of transient response experiments and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) characterization.