制备方法对Ce_(0.8)Zr_(0.2)O_2催化碳烟燃烧性能的影响

采用溶胶凝胶法、低温共沉淀法、高温共沉淀法、水热法和热分解法制备了5种Ce_(0.8)Zr_(0.2)O_2催化剂样品,用X射线粉末衍射(XRD)、BET、扫描电镜(SEM)、热重分析、H_2-TPR和O_2-TPO等技术对样品的结构、表面形貌、储氧性能、氧化还原性等进行表征,并对其催化碳烟燃烧活性进行评价,探究了制备方法对Ce_(0.8)Zr_(0.2)O_2催化性能的影响。结果表明:不同方法制备的Ce_(0.8)Zr_(0.2)O_2均能形成立方萤石结构的铈锆固溶体;制备方法对Ce_(0.8)Zr_(0.2)O_2催化剂的各项性能有显著影响,其中溶胶凝胶法有利于储氧能力和催化性能的提高,水热法有利于提高催化剂的比表面积,共沉淀法所制催化剂的储氧量及催化活性受温度的影响较大,总体催化效果较差,而热分解法制备的催化剂具有平整的表面结构,有利于提高机械强度。

EFFECT OF PREPARATION METHOD ON CATALYTIC ACTIVITY OF Ce0.8Zr0.2O2 CATALYSTS FOR SOOT COMBUSTION

A series of Ce0.8Zr0.2O2 catalysts were prepared by citric acid sol-gel method，low temperature co-precipitation method，high temperature co-precipitation method，hydrothermal method and thermal decomposition method. The structures, surface morphologies, oxygen storage capacities, and redox abilities of all catalysts were characterized by XRD, BET, SEM, thermogravimetric analysis, H2-TPR and O2-TPO. Potentials of the catalysts in the soot oxidation were evaluated by TPO analysis. The effects of preparation methods on the performance of catalytic soot combustion were investigated. The results indicate that the cerium zirconium solid solution with cubic fluorite structure is formed in all samples by all of the above methods. Sol-gel method is in favor of oxygen storage capacity and performance improvement; hydrothermal method helps improve the catalyst specific surface area; the catalyst prepared by thermal decomposition method has a flat surface structure which enhances the mechanical strength. However, the catalyst prepared by co-precipitation is poor in oxygen storage capacity and catalytic activity due to the influence of the temperature during the preparation.