不同锆源对Pd/Ce_(0.45)Zr_(0.45)La_(0.1)O_(1.95)整体式三效催化剂性能的影响(英文)

Effect of Zirconium Precursor on Performance of Pd/Ce_(0.45)Zr_(0.45)La_(0.1)O_(1.95) Three-Way Catalyst

分别以ZrOCO3,ZrO(NO3)2和Zr(NO3)4为锆源采用双氧水氧化-共沉淀法合成了Ce0.45Zr0.45La0.1O1.95储氧材料,并用湿法浸渍法制备了Pd/Ce0.45Zr0.45La0.1O1.95三效催化剂,用X射线衍射、拉曼光谱、N2吸附、X射线光电子能谱、氢气程序升温还原和氧脉冲等技术对该催化剂进行了表征.结果表明,以ZrOCO3和ZrO(NO3)2为锆源时所制催化剂上只能检测到单一的CeO2-ZrO2立方相,而以Zr(NO3)4为锆源制备的催化剂经老化后却能检测到四方相;另外,在模拟汽车尾气组分和工作条件下考察了整体型Pd/Ce0.45Zr0.45La0.1O1.9催化剂的三效活性.结果表明,以ZrOCO3为前驱体制备的整体式Pd/Ce0.45Zr0.45La0.1O1.9催化剂对C3H8,CO和NO具有最佳的催化活性.认为ZrOCO3更有利于Zr4+和La3+进入CeO2晶格形成均一固溶体,从而提高催化剂的高温稳定性和氧化还原性能.

Three types of Ce0.45Zr0.45La0.1O1.95 mixed oxides were prepared by H2O2-assisted precipitation using ZrOCO3,ZrO（NO3）2,and Zr（NO3）4 as precursors.The Pd/Ce0.45Zr0.45La0.1O1.95 three-way catalysts were prepared by the wet impregnation and characterized by the X-ray diffraction（XRD）,Raman spectroscopy,nitrogen adsorption,X-ray photoelectron spectroscopy（XPS）,temperature-programmed reduction（TPR）,and oxygen storage capacity.XRD and Raman spectroscopy results showed that the use of ZrOCO3 or ZrO（NO3）2 gave a CeO2-ZrO2 mixed oxide with a cubic phase of high thermal stability,while an extra t″-phase was observed in the aged Pd/Ce0.45Zr0.45La0.1O1.95 catalyst prepared using Zr（NO3）4.The activities of the three catalysts were evaluated using simulated exhaust gas under working conditions.The Pd/Ce0.45Zr0.45La0.1O1.95 catalyst prepared using ZrOCO3 as precursor gave the best activities for C3H8,CO,and NO conversion.The use of ZrOCO3 as precursor was better suited for the formation of Ce3＋ and more favorable for the homogeneous insertion of Zr4＋ and La3＋ into the CeO2 lattice,which resulted in better thermal stability and enhanced redox properties of the Pd/Ce0.45Zr0.45La0.1O1.95 catalyst.