基于定向固化与酸性位调控提升铈基催化剂抗砷中毒性能研究

In the field of control technology on stationary sources NOx emissions, denitration catalyst deactivation by arsenic poisoning is one of the key questions urgently to be solved. Researches show that arsenic poisoning effect is in close relationship with its inhibitory action on catalyst active sites. Consequently, the project is carried out on the basis of rare earth cerium— transition metal binary catalytic systems with eco-friendly ingredient and wide temperature window. Directional solidification and acid sites modulation are used as design thought to develop the way and method for improving arsenic tolerance by doping arsenic fixation additives and catalytic promoters. The structure-performance relationship on arsenic tolerance of novel catalysts are investigated by combining physicochemical characterizations with in-situ studies and theoretical calculations. The main clue of this project is that “investigation on arsenic poisoning mechanism of cerium-based catalysts— design and preparation of novel arsenic tolerance cerium-based catalysts— exploration on denitration mechanism and structure-performance relationship on arsenic tolerance of novel cerium-based catalysts”. According to the resolution of arsenic poisoning mechanism on cerium-based catalysts, the doping scheme is designed. After making a comprehensive survey of denitration and poisoning-resistant performance of catalysts, the way and preparation technology on enhancing arsenic tolerance of denitration catalysts have been obtained. Furthermore, denitration and poisoning-resistant performance of catalysts are correlated to their physical structure, surface acidity and redox property to illustrate the interactions among poison, active centers and additives as well as poisoning-resistant mechanism. It will shed new light on the development of novel arsenic tolerance denitration catalysts.

在固定源氮氧化物控制技术领域，脱硝催化剂易砷中毒失活是亟待解决的一个关键问题。研究表明，砷对催化剂活性位的抑制作用与其中毒失活效应密切相关。基于此，本项目拟以环境友好且温度窗口宽的稀土铈-过渡金属二元催化体系为基础，围绕定向固砷和酸性位调控的设计思路，通过固砷元素和催化助剂掺杂，获取提升抗砷中毒能力的途径和方法，并结合理化表征、原位分析和理论计算，探究新型催化剂抗砷构效关系。以“铈基催化剂砷中毒失活机制研究—新型抗中毒铈基催化剂设计与制备—新型铈基催化剂脱硝机理与抗砷中毒构效关系探究”为主线，在解析砷致铈基催化剂中毒失活机制基础上，设计掺杂改性方案，综合考察催化剂脱硝和抗中毒性能，获取改进脱硝催化剂抗砷性能的途径和制备工艺。进一步地，将催化剂物性结构、表面酸性、氧化还原性与脱硝和抗中毒性能进行关联，明确毒物与活性位及助剂之间的作用效应，阐明抗中毒机制，为研制新型抗砷中毒脱硝催化剂提供思路。

氧化铈由于其生理毒性小，表面氧空位丰富和储氧性能优异，其与过渡金属元素掺杂制备的复合金属氧化物催化剂具有NH3-SCR应用价值，是传统钒钨钛脱硝催化剂的良好替代品。然而，烟气中重金属砷的存在仍是造成铈基脱硝催化剂中毒失活的重要原因之一。在明确催化剂砷中毒失活主控因素是氧化还原性变化和酸性损失的基础上，本项目以定向固砷和酸性位调控为策略，以“铈基催化剂砷中毒失活机制研究—新型抗中毒铈基催化剂设计与制备—新型铈基催化剂脱硝机理与抗砷中毒构效关系探究”为主线开展研究，开发了具有优异抗砷中毒性能的新型铈钨铝脱硝催化剂。通过固砷助剂铝掺杂，在催化剂上构筑定向固砷位点，阻断砷与活性中心结合；通过助剂浓度、引入方式和活性组分比例的调控，获取了最优催化剂制备工艺。可实现空速270000 h-1和2.1 wt%毒物砷存在条件下，300~400 ℃温度范围内，90%以上的高脱硝活性保持，同时副产物N2O产量降低70%。利用多表征分析，建立了催化剂物性结构、酸性/氧化还原性与抗中毒性能之间的关联，阐明催化剂抗砷中毒机制，为烟气脱硝催化剂开发提供新思路。此外，本项目还拓展了的抗砷中毒催化剂制备工艺的应用领域，用于开发高化学稳定性的耐苛刻条件的催化剂，并开发了相应的砷中毒催化剂的再生药剂及可控再生策略，实现了催化剂的资源化回收，有效降低了运行成本。