| 摘 要： | Pd/γ-Al_2O_3–TiO_2 catalysts containing various compositions of titania and alumina were prepared by sol–gel and wet-impregnation methods in attempt to study the particle size, nature of phases, morphology and structure of the composite samples. The ethanol oxidation experiments, N_2 adsorption–desorption,FTIR, XRD and XPS were conducted, and the effects of Al_2O_3 content on the surface area, phase transformation and structural properties of TiO_2 were investigated. The optimal value of ethanol conversion appeared on Pd/Al(0.05)–Ti and Pd/Al(0.90)–Ti catalysts irrespective of the ethanol oxidation temperature, and we call this as a double peaks phenomenon of catalytic activity. The XRD results reveal that the phase composition and crystallite size of the mixed oxides depend on Al_2O_3/TiO_2 ratio and calcination temperature. Al_2O_3 can effectively prevent the agglomeration of TiO_2 and this can be ascribed to the formation of Al–O–Ti chemical bonds in Al_2O_3–TiO_2 crystals. Binding energy and Pd surface concentration of the catalysts were modified apparently, which may also lead to catalyst activity changes.
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