CeO2基柴油车脱硝催化材料的设计制备及老化机理研究

The control of nitrogen oxides is one of the key challenges of the diesel exhaust emission pollution reduction. The current catalysts for diesel vehicle DeNOx, such as vanadium-based and zeolite-based catalysts, have some serious problems difficultly to be solved: vanadium component is toxic, and zeolites have poor hydrothermal stability and are easily poisoned by hydrocarbons. In the present project, CeO2-MOx（MOx：SO42-、PO43-、WO3、Nb2O5） catalyst with core-shell structure is synthesized, in which the core CeO2 is synthesized by spray drying method and the shell MOx is loaded by impregnation.The catalyst with high sulfur and hydrothermal resistance, owns over 80% NOx conversions in 200-500 ℃. The interface arising from the strong interactions between CeO2 and MOx facilitates the formation of interface with high thermal stability and excellent oxygen diffusion characteristics, leading to the high hydrothermal stability of catalyst. The composite of MOx and the core-shell structure further enhance the acidity and the aging resistance of catalysts. The structure-activity relationship among the structure, acidity, adsorption, redox and NH3-SCR activities of catalysts is researched. Basically, the mechanism for catalyst with high sulfur resistant and hydrothermal stability is discussed.

氮氧化物控制是柴油车尾气污染减排的关键难题之一，目前柴油车脱硝用的钒基催化材料有毒而沸石催化材料的碳烃中毒问题难以解决。项目通过喷雾干燥法制备超细球形CeO2，采用浸渍法在CeO2表面负载MOx（MOx：SO42-、PO43-、WO3、Nb2O5）进而制备出具有核壳结构的CeO2固体酸催化材料，该材料在200-500℃温度范围内具有超过80%的脱硝效率及优良的水热稳定性和抗SO2中毒性能。通过催化材料核壳间的强结构相互作用生成具有高热稳定性和优良氧扩散性能的界面层来提高材料的水热稳定性，同时发挥CeO2的储放氧性能和MOx对NH3的强吸附特性；通过材料的核壳结构和不同MOx的复合提高材料的表面酸度及抗老化性能；通过深入研究催化材料结构、表面酸碱位强度、吸附性能、redox性能与NH3-SCR脱硝性能之间的构效关系，探讨催化材料的抗水热老化及硫中毒机理。

项目研究内容属于柴油车尾气氮氧化物减排的SCR脱硝技术关键材料，针对目前柴油车脱硝用的钒基催化材料有毒而沸石催化材料的碳烃中毒问题，通过喷雾干燥法制备超细球形CeO2，采用浸渍法在CeO2 表面负载酸性组分MOx（MOx：SO42-、PO43-、WO3、Nb2O5）进而制备出了具有核壳结构的CeO2 固体酸催化材料。其中，项目开发的磷酸锆（10wt.%）负载CeO2-ZrO2材料在250-450℃温度范围内具有超过80%的脱硝效率和N2选择性及优良的水热稳定性和抗SO2/K 中毒性能，而NbOx-CeO2/WO3-TiO2的低温活性更优异，在200-400℃温度范围内具有超过80%的脱硝效率。催化材料核壳间的强结构和电子相互作用有利于提高材料的表面酸度、热稳定性，并促进晶格氧的扩散性能，同时发挥CeO2 的储放氧性能和MOx 对NH3 的强吸附特性；通过材料的核壳结构和不同MOx 的复合，如磷酸根与锆原子预结合，可以抑制MOx与CeO2组分的固相反应，有效提高材料的表面酸度及抗老化性能。.NH3-SCR反应机理研究结果表明，铈基固体酸催化剂表面NH3和NOx共吸附（NH3吸附在酸性组分上，NOx吸附在铈位上）具有重要作用，阐明了“NH4NO3”为此类催化剂表面NH3-SCR反应的重要中间物种，酸性组分不但提高催化剂表面酸度而且促进了铈基催化剂表面硝酸铵的分解。此外，必须强调的是，铈基催化剂表面NH3吸附并被活化始终是NH3-SCR反应的核心步骤。.项目发表SCI论文13篇，申请专利3项，授权专利3项，培养博士后1人、博士2人、硕士3人，参加国际学术会议1次并做口头报告，参加国内学术会议2次（做口头报告1次）。