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SO2 Poisoning Mechanism of the Multi-active Center Catalyst for Chlorobenzene and NOx Synergistic Degradation at Dry and Humid Environments
Environmental Science & Technology ( IF 11.4 ) Pub Date : 2021-09-15 , DOI: 10.1021/acs.est.1c03617
Guobo Li 1 , Kai Shen 1 , Peng Wu 1 , Yaping Zhang 1 , Yaqin Hu 1 , Rui Xiao 1 , Bing Wang 1 , Shule Zhang 2
Affiliation  

The performance of fresh (PdV/TiO2), sulfur poisoned (Used-S and Used-H), and regenerated (Used-RS and Used-RH) multi-active center catalysts for chlorobenzene catalytic oxidation and selective catalytic reduction (CBCO + SCR) reaction is investigated. The reaction on the catalyst surface is blocked after sulfur poisoning owing to the occupation and deposition of catalyst active centers (mainly Pd centers) by PdSO4 (and/or PdS in a dry environment) and NH4HSO4 species, especially the CBCO process. Sulfates (mainly NH4HSO4) on the sulfur poisoned catalyst surface are partially decomposed after 400 °C thermal regeneration, while the deactivation caused by the formation of PdSO4 species is irreversible. Density functional theory calculation results show that in the PdSO4 and NH4HSO4 generation paths, each step of the elementary reaction has just a small energy barrier to overcome, and the stability of the product for each elementary reaction increases gradually. Even worse, SO2 is easily combined with H2O gas molecules to form H2SO3 in a humid environment, and the energy barrier for conversion of SO32– to SO42– is just 0.041 eV. The two oxygen vacancies (VOx-1 or TiOx-1) provide adsorption sites for CBCO + SCR reaction gas molecules but do not exhibit adsorption properties for SO2, which gives a possible idea for optimization of sulfur resistance. The present work is favorable for further synergistic removal of CB/NOx by the catalyst for anti-SO2 poisoning modification and application in the manufacture industry.

中文翻译:

干湿环境下氯苯与NOx协同降解多活性中心催化剂SO2中毒机理

新鲜(PdV/TiO 2)、硫中毒(Used-S 和 Used-H)和再生(Used-R S和 Used-R H)多活性中心催化剂对氯苯催化氧化和选择性催化还原的性能( CBCO + SCR) 反应进行了研究。由于催化剂活性中心(主要是 Pd 中心)被 PdSO 4(和/或干燥环境中的 PdS)和 NH 4 HSO 4物质占据和沉积,尤其是 CBCO 过程,硫中毒后催化剂表面的反应被阻断. 硫酸盐(主要是 NH 4 HSO 4) 硫中毒催化剂表面在 400 °C 热再生后部分分解,而由 PdSO 4物种形成引起的失活是不可逆的。密度泛函理论计算结果表明,在PdSO 4和NH 4 HSO 4生成路径中,基元反应的每一步都只需要克服一个很小的能垒,每个基元反应产物的稳定性逐渐增加。更糟的是,SO 2易于用H组合2 O气体分子形成ħ 2 SO 3在潮湿环境中,并且能量屏障的SO转换3 2-至SO4 2–仅为 0.041 eV。两个氧空位(VO x -1或 TiO x -1)为 CBCO + SCR 反应气体分子提供了吸附位点,但对 SO 2不表现出吸附特性,这为优化抗硫性提供了可能的思路。该工作有利于该催化剂进一步协同脱除CB/NO x用于抗SO 2中毒改性及在制造工业中的应用。
更新日期:2021-10-06
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