多孔钙钛矿的理性设计及其选择性催化还原NOx

The purification of automobile exhaust gases, which can cause smog and haze, is regarded as an important objective for air pollution control. Recently, the development of lean-burn engine has become the trend of fuel-efficient and environmental protection. Efficient de-NOx catalyst in lean-burn condition is the key of pollution control. HC-SCR technology has potential application. The industrial application of perovskite-type HC-SCR catalyst is restricted due to its low activity, in spite of its high stability. The intention of the present program is to improve the catalytic activity of perovskite by substitution and morphology control. Surface properties, oxygen species and redox properties can be regulated. In addition, adsorption sites and intermediates are affected, which further lead to higher catalytic activity. Characterizations and catalytic activity test are conducted on A/B site doped YFeO3. The effects of substitution on reaction pathway and catalytic activity are revealed. Porous YFeO3 catalysts are prepared by casein-templated method. The effects of synthesis conditions on binding sites, secondary structure of casein and structure of micelles are investigated. The mechanism of regulation of perovskite’s structure and morphology is clarified. The effects of structure, morphology and pore size on redox properties, oxygen species, surface properties and catalytic activity are investigated through characterizations. The “substitution, structure and morphology-catalytic activity” relationship is clarified, which provides powerful theoretical foundation for rational design of perovskite catalysts.

汽车尾气是造成雾霾的重要因素，其防治紧迫性凸显。当前稀燃发动机技术成为节油环保主流趋势，稀燃条件下高效催化脱除NOx已成污染控制关键。HC-SCR技术极具应用前景，钙钛矿型催化剂稳定性高，然而低活性导致应用受限。本项目拟通过A、B位掺杂和形貌控制，调控YFeO3的表面性质、氧物种、氧化还原性等物理化学性质，从而影响反应的吸附位点和中间产物的转化，进而提高催化活性。对A、B位掺杂的YFeO3进行表征和催化活性测试，揭示掺杂对HC-SCR的反应路径和催化活性的作用机制。采用酪蛋白模板法合成多孔YFeO3催化剂，研究合成条件对金属离子结合位点、酪蛋白结构的影响规律，揭示其对钙钛矿结构形貌的调控机制；通过表征手段研究结构、形貌、孔径对催化剂氧化还原性能、氧物种、表面性质、催化活性的影响。通过对YFeO3“掺杂、结构形貌---催化活性”作用机制的阐述，为今后理性设计钙钛矿型催化剂提供有利的理论指导。

为减少汽车尾气污染，稀燃发动机技术成为节油环保主流趋势，HC-SCR技术是稀燃条件下高效催化脱除NOx的方法之一，其核心技术是催化剂。钙钛矿型催化剂稳定性高，然而低活性导致应用受限。本项目针对钙钛矿催化剂比表面积低、活性低的问题，通过A、B位掺杂和形貌控制，调控YFeO3的物理化学性质，从而提高催化活性。对YFeO3进行了A位（Ce、Sr、Eu）掺杂和B位（Cu）掺杂，筛选掺杂元素，并对催化剂的理化性质和催化性能进行表征，探讨催化机理，优化出最佳掺杂的催化剂Y0.8Eu0.1Ce0.1Fe0.9Cu0.1O3。采用酪蛋白模板法合成催化剂，通过改变温度、柠檬酸、pH值、酪蛋白浓度和金属盐浓度，对催化剂的结构形貌进行调控，制备出五种不同形貌的YFeO3钙钛矿催化剂：微球、网状、片状、柱状、纳米颗粒。对酪蛋白进行了微结构表征，发现合成条件通过影响酪蛋白胶束的形貌，进而调控钙钛矿的形貌。对合成机理进行了表征和讨论，结果表明酪蛋白模板和柠檬酸-金属离子复合物之间主要以静电吸引力和氢键相结合，在不同合成条件下，酪蛋白在前驱体溶液中均发生了伸展，疏水性、二级结构、巯基含量和二硫键含量发生了变化，酪蛋白的构象发生了变化，使得酪蛋白模板与金属前驱体的结合发生了变化。对不同结构形貌的催化剂进行物理化学性质表征和催化机理研究，其中网状和多孔微球形貌的催化剂具有更高的HC-SCR催化活性。发表论文6篇，授权国家发明专利1项，申报国家发明专利1项，培养研究生4名。