Pt/MOx-SiO2 (M=Ce,Zr, Al)催化剂对CO和C3H8氧化性能的影响

采用共沉淀法制备质量比为1:1的MOx-SiO2(M=Ce,Zr,Al)复合氧化物,以此为载体采用浸渍法制备了铂基氧化型催化剂.考察了该系列催化剂在模拟柴油车尾气条件下,经SO2硫化前后对C3H8和CO的氧化性能.用X射线衍射(XRD)、低温N2吸附-脱附、氨气/氧气/二氧化碳程序升温脱附(NH3/O2/CO2-TPD)和X射线光电子能谱(XPS)等手段进行了表征.NH3-TPD证实催化剂表面存在多种酸中心,硫化后催化剂表面中强酸中心增多.O2-TPD证实催化剂表面存在α和β氧物种,硫化后催化剂表面氧脱附量减少.其中Pt/Al2O3-SiO2表面酸性最弱和表面氧脱附量最大.XPS结果表明新鲜催化剂经硫化后会使催化剂表面Pt的结合能降低.活性测试结果表明,三种催化剂对CO和C3H8的催化氧化活性均较好,其中Pt/ZrO2-SiO2抗SO2中毒性能最佳,具有良好的应用前景.

Performance Effect of Pt/MOx-SiO2 (M=Ce, Zr, Al) Catalysts for CO and C3H8 Oxidation

MOx-SiO2(M=Ce,Zr,Al) mixed oxides with a MOx:SiO2 mass ratio of 1:1 were prepared by co-precipitation.Pt-only diesel oxidation catalysts supported on these mixed oxides were obtained by the incipient wetness method.The catalytic activities in simplified diesel exhaust gas before and after SO2 treatment were analyzed.The catalysts were characterized by X-ray diffraction,N2 adsorption-desorption,NH3/O2/CO2 temperature programmed desorption(NH3/O2/CO2-TPD) and X-ray photoelectron spectroscopy(XPS).The results of NH3-TPD suggested that the surface of the catalysts had multiple acidic sites,and the number of medium-strength acidic sites increased following treatment with SO2.The results of O2-TPD revealed that there were α and β oxygen species in the catalysts,and the amount of O2 desorption decreased for the SO2-treated catalysts.The Pt/Al2O3-SiO2 catalyst exhibited the lowest surface acidity and the largest amount of oxygen desorption.XPS indicated that the binding energy of Pt 4f5/2 decreased when the catalysts were treated with SO2.All the catalysts showed excellent activity for CO and C3H8,and the Pt/ZrO2-SiO2 catalyst exhibited the best SO2 poisoning resistance,showing the potential for these catalysts to be applied in diesel oxidation.