新型核壳结构MOFs@TiO2中低温脱硝催化剂表面物化性质调控和抗硫性能研究

Selective catalytic reduction with (NH3) NH3-SCR is one of the main methods to abating NOx from stationary sources and the catalyst is one of keys for the method. Metal-organic frameworks materials (MOFs), which own high specific surface area, abundant acid sites, high thermal stability (when temperature lower than 350 °C), high reduction ability and so on, are thought to be potential alternatives for SCR catalysts used in medium- and low-temperature (<300 °C). However, the poor SO2 tolerance have limited the application of these catalysts in industry. In this project, we consider the unique structure and properties of core-shell materials, try to use TiO2 which owns high tolerance of SO2 as shell material and synthetize new MOFs@TiO2 core-shell materials, and achieve the control of material’s physicochemical properties by controlling properties of the TiO2 shell, then the material’s surface will own suitable acid-base and oxidation-reduction property, thus increasing the SO2 tolerance and enlarge the temperature window of the catalysts. The adjustment theory and method of material’s physicochemical properties will be built. The effects of physicochemical properties on catalytic activity will be analyzed in deep and thus reveal the theory of the increase of performance. The structure-activity relationship and the reaction mechanism will be researched. The research results support scientific evidence and the synthesis of SCR catalysts with high SO2 tolerance.

氨气选择性催化还原（NH3-SCR）技术是目前固定源烟气脱硝的主流技术，催化剂是该技术的核心。金属有机框架结构材料（MOFs）具有比表面积高、酸性位丰富、热稳定性高（温度<350°C）、氧化还原性强等优点，在中低温（<300°C）SCR反应中显示出较好的应用潜力，但较低的抗硫性能限制了其进一步应用。本课题依据核壳材料独特的结构和特性，拟将MOFs和具有优异抗硫能力的TiO2有机结合，构建新型MOFs@TiO2核壳结构材料，通过控制TiO2壳层特性、结构等方式对材料表面物化性质进行调控，以期获得具有适宜表面酸碱性和氧化还原性的复合材料，提高催化剂的抗硫耐水蒸气性能并扩宽其温度窗口。在此基础上，建立核壳结构材料物化属性的调控理论和方法，阐明其对催化性能的影响规律，揭示性能强化机制，研究催化剂构效关系并探讨反应机理。研究成果有望为制备抗硫性能强的中低温SCR催化剂提供科学依据和技术储备。

氮氧化物（NOx）是引起灰霾和臭氧形成的重要前驱体，为我国主要的大气污染物之一。氨气选择性催化还原法（NH3-SCR）是目前固定源控制NOx的主流技术，催化剂是该技术的核心之一。金属有机框架结构材料（MOFs）具有比表面积高、酸性位丰富和氧化还原性强等优点，在催化反应中可以显示出较高的活性。本项目采用溶剂热法和微波法制备了多种MOFs材料，比较了MOFs材料在NH3-SCR中的活性，发现Cu3(BTC)2在NH3-SCR反应中可以显示出较高的活性。然后通过优化制备条件，合成了MOFs@TiO2等核壳结构催化剂并将其用于NH3-SCR反应中。核壳结构有利于催化剂表面形成更多的氧空位和酸性位，从而有利于催化剂在中低温的活性；核壳结构催化剂上的NH3-SCR反应同时遵循L-H和E-R机理。在催化剂抗硫性能方面，以铼基催化剂为例，采用实验和理论计算研究了催化剂具有优异抗硫性能的原因；通过抑制催化剂表面SO2的吸附可以使催化剂在NH3-SCR反应中显示出优异的抗硫性能。