No abstract

The effect and the role of alkaline earth metals added to Ag/SiO 2 catalyst were studied in the gas-phase catalytic oxidation of benzyl alcohol. The main oxidation product was benzaldehyde, together with only small amounts of CO 2 , benzene, and toluene, depending on the reaction conditions. The influence of the method regarding how to add the alkaline earth metal to the supported Ag catalyst, and the amount of the added alkaline earth metal on the partial oxidation activity, was investigated, along with the analyses of these alkaline earth metal added Ag/SiO 2 catalysts by diffuse reflectance (DR) spectroscopy, XRD, thermal gravimetricdifferential thermal analyses (TG-DTA), and extended X-ray absorption fine structure (EXAFS). The addition of alkaline earth metals such as Ca, Sr, and Ba to the Ag/SiO 2 catalyst by a coimpregnation method significantly promoted the catalytic activity of the partial oxidation of benzyl alcohol. The surface oxygen species on the supported Ag played an important role in the partial oxidation of benzyl alcohol on the basis of the results of the transient response experiment and the O 2 adsorption on the prereduced Ag/SiO 2 catalysts with and without alkaline earth metal. The alkaline earth metal added to the Ag/SiO 2 catalyst was suggested to inhibit the formation of carbonaceous material, make the metallic Ag disperse, and facilitate the adsorption of oxygen on the Ag surface to form an oxygenated Ag surface, which was thought to be responsible for the partial oxidation of benzyl alcohol.