Insights into the enhanced activity and SO2 resistance of air oxidation treated Mn-Fe doped biochar catalyst in the low-temperature catalytic reduction of NOx with NH3

• Published in: Fuel (Guildford) 2024-02, Vol.357, p.129989, Article 129989
• Main Authors: Zhou, Tongxiao, Liu, Lu, Wang, Bangda, Ma, Shenggui, Dai, Zhongde, Jiang, Wenju, Jiang, Xia
• Format: Article
• Language: English
• Subjects: H2O and SO2 resistance; Low-temperature NH3-SCR; Mn-Fe doped biochar; Two-stage air oxidation
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2023.129989

•A two-stage air oxidation consisting of pre- and post-oxidation method was employed to prepare Mn-Fe doped porous biochar catalyst.•The SBET, pore property, Mn dispersity, redox ability and surface acidity of catalyst were comprehensively developed.•The catalyst showed highly enhanced NO conversion rate of 91.3% and desirable SO2 and/or H2O resistance.•Two-stage air oxidation strengthened the synergistic interaction between Mn and Fe.•O-containing groups introduced by air oxidation promoted the adsorption of NH3 and NO while decreased the adsorption of SO2. In this study, a sustainable two-stage air oxidation (TAO) was employed to prepare Fe modified MnOx-biochar catalyst (C-O2-MF-O2) instead of high temperature treatment and/or chemical activation for selective catalytic reduction of NO with NH3 (NH3-SCR). The collaborative effect of Fe modification and TAO on the physicochemical properties and catalytic performance of catalysts was systematically studied. Compared with counterpart catalysts treated with two-stage N2 (C-N2-MF-N2) or one-stage O2 (C-O2-MF-N2, C-N2-MF-O2), C-O2-MF-O2 showed obvious enhanced physicochemical properties (SBET, pore properties, high-valance metal ratio, chemisorption oxygen (Oα) content), superior catalytic performance, achieving 91.3% NO conversion with nearly 100% N2 selectivity at 150 °C, and much better H2O and SO2 resistance. It is worth noting that TAO facilitated the redox performance of MnOx after Fe modification to generate more dispersed high-valance metal (Mn4+ and Fe3+), thereby favoring the low-temperature SCR activity of the catalyst. Further, the in situ DRIFTS studies revealed TAO produced remarkable effects on the adsorption behaviors of NH3, NO and SO2, and the corresponding mechanisms of catalyst activity enhancement and SO2 resistance were proposed. Generally, TAO could be a favorable avenue to prepare catalysts with binary active metals for improving performance of NH3-SCR.