Traditional Rigid Supports Such As Al₂O₃and SiO₂Modified By SnO₂in Bulk Phase As Supports For Pd For CO And CH₄Oxidation

CO and CH4is a highly toxic gas, which can pollute the air atmosphere if emitted without treatment. Catalytic oxidation has been proved to be a most effective way to abate CO and CH4pollution. A series of SnO2-MxOy(M=Al, Si) composite metal oxide supports with different Sn/M(M=A1, Si) atomic ratios were synthesized with co-precipitation method and used as supports for Pd to prepare catalysts for CO oxidation. The samples were characterized by N2adsorption-desorption, X-ray Powder Diffraction (XRD), H2temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) techniques. It was found that Al3+can be introduced into the crystalline lattice of tetragonal rutile SnO2to effectively form solid solution structure. As a consequence, SnO2-MxOy(M=Al, Si) binary supports with significantly improved thermal stability, enlarged surface areas, enhanced texture structure and containing more active surface oxygen species can be obtained. SnA173, a support with a Sn/Al atomic ratio of7/3, was found to be the best support in CO oxidation reaction due to its certain large surface area and the presence of suitable amount of reducible oxygen species. With this support, the two major reasons accounting for the activity, that is, Pd dispersion and strong metal support interaction (SMSI) between Pd and the support, are believed to be tuned optimally. Water vapor has reversible negative effect on the CO oxidation activity of Pd/SnA173catalyst, but which is mitigated evidently by the presence of SnO2. In addition, no any permanent deactivation occurs to Pd/SnA173catalyst during a60hours’test in the presence or in the absence of water vapor, indicating this optimized SnO2-Al2O3support has a strong potential to be applied in some practical processes for exhaust clean. In summary, SnO2-Al2O3composite metal oxides with suitable Sn/Al atomic ratios are better supports than individual Al2O3and SnO2, on which less amount of Pd could be used to achieve supported Pd catalysts with rival performance. Furthermore, with same method, SnO2modification on another traditional rigid support, SiO2, was also investigated in this study.