Ye Lyumeng, Lu Peng, Peng Yue, Li Junhua, Huang Haibao
School of Environmental Science and Engineering, Sun Yat-sen University, 510275 Guangzhou, PR China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, South China Institute of Environmental Sciences, The Ministry of Ecology and Environment of PRC, 510655 Guangzhou, PR China.
The Key Laboratory of Water and Air Pollution Control of Guangdong Province, South China Institute of Environmental Sciences, The Ministry of Ecology and Environment of PRC, 510655 Guangzhou, PR China; Guangdong Province Engineering Laboratory for Air Pollution Control, South China Institute of Environmental Sciences, The Ministry of Ecology and Environment of PRC, 510655 Guangzhou, PR China.
J Hazard Mater. 2021 Aug 15;416:125939. doi: 10.1016/j.jhazmat.2021.125939. Epub 2021 Apr 28.
An increasing number of industries remove toluene from flue gas by the existing NH-selective catalytic reduction (NH-SCR) units. A thorough probe into the impact of NO and NH addition on toluene oxidation is imperative but still lacks a unified understanding. In this work, NH-SCR reactants are found to inhibit the toluene oxidation process over the MnO-CeO catalyst below 200 °C. The competitive adsorption between NH-SCR reactants and toluene, the NO adsorption state, and carbon deposition are emphasized to play important roles in this deactivation. Within the NO adsorption states, only the adsorbed NO can enhance the toluene oxidation. The formed nitrate species (NO) on the surface is inactive. NO adsorption is the weakest among the reactants with the smallest adsorption energy of -0.42 eV, restricting its promotion on toluene oxidation. NO and NO are both demonstrated to be inefficient to oxidize toluene. Meanwhile, MnO-CeO catalyst suffers from serious acetonitrile and benzonitrile poisoning. The amount of nitrile species accounts for ~95% of total carbon deposition, while no simple substance carbon (C) can be generated from CO disproportionation. Special care should be considered towards the formation of environmentally hazardous benzamide in the off-gas from the simultaneous NO and toluene removal process.
越来越多的行业通过现有的氨选择性催化还原（NH-SCR）装置从烟气中去除甲苯。深入探究添加NO和NH对甲苯氧化的影响势在必行，但目前仍缺乏统一认识。在本研究中，发现NH-SCR反应物在200°C以下会抑制MnO-CeO催化剂上的甲苯氧化过程。强调NH-SCR反应物与甲苯之间的竞争吸附、NO的吸附状态以及碳沉积在这种失活过程中起重要作用。在NO的吸附状态中，只有吸附态的NO能促进甲苯氧化。表面形成的硝酸盐物种（NO）无活性。NO在反应物中吸附最弱，吸附能最小为-0.42 eV，限制了其对甲苯氧化的促进作用。NO和NO均被证明对氧化甲苯效率低下。同时，MnO-CeO催化剂会遭受严重的乙腈和苯腈中毒。腈类物种的量占总碳沉积量的约95%，而CO歧化不会生成单质碳（C）。在同时去除NO和甲苯的过程中，应特别关注废气中对环境有害的苯甲酰胺的形成。
