State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, International Joint Laboratory of Catalytic Chemistry, College of Sciences, Shanghai University, Shanghai 200444, China.
National Nanotechnology Center, National Science and Technology Development Agency, Klong Luang, Pathum Thani 12120, Thailand.
Environ Sci Technol. 2022 Apr 19;56(8):5141-5149. doi: 10.1021/acs.est.1c08096. Epub 2022 Apr 3.
The catalyst deactivation caused by the coexistence of alkali and heavy metals remains an obstacle for selective catalytic reduction of NO with NH. Moreover, the copoisoning mechanism of alkali and heavy metals is still unclear. Herein, the copoisoning mechanism of K and Cd was revealed from the adsorption and variation of reaction intermediates at a molecular level through time-resolved spectroscopy combined with theoretical calculations. The alkali metal K mainly decreased the adsorption of NH on Lewis acid sites and altered the reaction more depending on the formation of the NHNO intermediate, which is highly related to NO adsorption and activation. However, Cd further inhibited the generation of active nitrate intermediates and thus decreased the NO abatement about 60% on potassium-poisoned CeTiO catalysts. Physically mixing with acid additives for CeTiO catalysts could significantly liberate the active Lewis acid sites from the occupation of alkali metals and relieve the high dependence on NO adsorption and activation, thus recovering the NO removal rate to the initial state. This work revealed the copoisoning mechanism of K and Cd on Ce-based de-NO catalysts and developed a facile anti-poisoning strategy, which paves a way for the development of durable catalysts among alkali and heavy metal copoisoning resistant catalytic reduction of NO.
碱金属和重金属共存引起的催化剂失活仍然是 NH 选择性催化还原 NO 的障碍。此外，碱金属和重金属的共中毒机制仍不清楚。在此，通过时间分辨光谱结合理论计算，从吸附和反应中间体的变化在分子水平上揭示了 K 和 Cd 的共中毒机制。碱金属 K 主要通过降低 NH 在路易斯酸位上的吸附以及更多地依赖于 NHNO 中间物的形成来改变反应，这与 NO 的吸附和活化密切相关。然而，Cd 进一步抑制了活性硝酸盐中间体的生成，从而使钾中毒的 CeTiO 催化剂上的 NO 去除率降低了约 60%。对于 CeTiO 催化剂与酸性添加剂的物理混合，可以显著将活性路易斯酸位从碱金属的占据中解放出来，并减轻对 NO 吸附和活化的高度依赖，从而将 NO 去除率恢复到初始状态。这项工作揭示了 Ce 基脱硝催化剂中 K 和 Cd 的共中毒机制，并开发了一种简便的抗中毒策略，为开发耐碱和重金属共中毒的 NO 选择性催化还原的耐用催化剂铺平了道路。
