Abstract:

Selective catalytic reduction (SCR) is the most mature technology for flue gas denitrification in power plants, and the catalyst is the core. Arsenic poisoning is one of the most important sources for the deactivation of the catalyst. This review summarizes the physical and chemical deactivation mechanisms of the arsenic poisoned SCR catalysts. The physical deactivation is attributed to the deposition and oxidation of gaseous arsenic oxides over the surface of the catalysts, and the chemical deactivation is ascribed to the destruction of active acid sites caused by the arsenic species. Then, the development of SCR catalysts with the capability of anti-arsenic poisoning is presented, including the adjustment of the pore structures in the catalyst, optimization of the chemical formulation of the catalyst, and solidification of gaseous arsenic oxide. MoO₃ is the optimal active agent, metal ions such as Bi, In, Sn and Mg are the main additives for anti-arsenic poisoning, and Ca species is the effective sorbent for the gaseous arsenic species. Finally, the regeneration technologies for poisoned catalysts are briefly discussed, including the wet-solution washing, thermal reduction and the combination of multiple regeneration methods, among which the combination of mechanical blowing, wet-solution washing and active components implantation is widely utilized in the industrial processes at present. This review can provide fundamental instructions for the development of SCR catalysts for anti-arsenic poising.

Key words: selective catalytic reduction (SCR), catalyst, arsenic poisoning, anti-arsenic poisoning, regeneration

摘要：

选择性催化还原（SCR）是目前应用最为广泛的烟气脱硝技术，催化剂是整个SCR脱硝系统的核心。在实际应用过程中，催化剂存在各种失活问题，其中砷中毒是催化剂失活的重要原因之一。本文详细阐述了SCR脱硝催化剂砷中毒的物理和化学失活机理，其中物理失活是由于As₂O₃在催化剂表面沉积、氧化造成催化剂孔道堵塞所致，而化学失活是由于砷氧化物破坏催化剂酸位点、改变活性基团形态、降低催化剂氨吸附及氧化还原能力所致。然后，系统介绍了抗砷中毒SCR脱硝催化剂的研发路线以及现有抗砷中毒催化剂优化改进的主要技术手段，主要包括调整催化剂孔隙结构、优化催化剂化学配方和烟气侧砷氧化物吸附固化等，其中MoO₃是优选的催化剂活性助剂，金属元素（如Bi、In、Sn、Mg）是主要的抗砷助剂，钙基物质是典型的烟气侧砷氧化物吸附添加剂。最后，对砷中毒废弃催化剂的再生技术进行了简要介绍，包括湿法清洗、热还原法、复合再生等，在实际工业应用中，主要以物理清扫、湿法清洗配合活性组分添加的复合再生方式实现中毒催化剂再生。本文可对未来抗砷中毒SCR脱硝催化剂的研发与优化提供重要支撑。

关键词: 选择性催化还原, 催化剂, 砷中毒, 抗砷中毒, 再生