Study on Preparation, Characterization and Behaviors of WO_3-TiO_2/SiO_2 for Photocatalytic Reaction of Methane with Water

TiO_2/SiO_2 were prepared by the chemical modification reaction on SiO_2, then the supported coupled semiconductors WO_3-TiO_2/SiO_2 were prepared by impregnating TiO_2/SiO_2. The gas-phase photocatalytic production of CH_3OH and H_2 from CH_4 and H_2O on WO_3-TiO_2/SiO_2 has been studied using a fixed-bed annular photoreactor under UV irradiation. The surface structure, photon adsorption property and chemisorption ability of WO_3-TiO_2/SiO_2 have been investigated by the techniques of XRD, TPR, BET, UVDRS, IR and TPD. It was showed that the band-gap energy of well-dispersed surface species on SiO_2 can be increased due to the quantum size effect; the interaction between WO_3 and TiO_2, leading to the formation of W-O-Ti bonds, can improve the photon adsorption properties and the chemsorption abilities of CH_4 and H_2O effectively; the photon-surface-thermal synergistic action can be formed on WO_3-TiO_2/SiO_2 at temperature higher than 100 ℃ under UV irradiation, which can promote methane adsorption as dissociative states by photoactive O~-, thus WO_3-TiO_2/SiO_2 has the higher photocatalytic activity with the methanol selectivity of more than 83%.