Study on photocatalysts for synthesis of methanol and hydrogen from methane with water

TiO_2/SiO_2 were prepared by the chemical modification reaction on SiO_2,then the supported coupled semiconductors(MoO_3,ZnO)-TiO_2/SiO_2 were prepared by isovolumic impregnating TiO_2/SiO_2. The surface structure,chemical adsorption capabilities,photon absorption properties and photocatalytic behaviors of MoO_3-TiO_2/SiO_2 and ZnO-TiO_2/SiO_2 were systematically investigated by the techniques of X-ray differaction(XRD),BET,temperature programmed reduction(TPR),UV-Vis DRS,IR and temperature programmed desorpsion(TPD).The surface species of MoO_3-TiO_2/SiO_2 and ZnO-TiO_2/SiO_2,comprising Mo—O—Ti and Zn—O—Ti bonds respectively,have the quantum size effects due to the supports interaction.The supported coupled semiconductors MoO_3-TiO_2/SiO_2 exhibits higher photocatalytic activity than ZnO-TiO_2/SiO_2,because chemisorption property of CH_4 and utilization of the photo energy enhanced effectively when MoO_3 was incorporated on TiO_2/SiO_2.CH_3OH and H_2 are produced by the gas-phase photocatalytic reaction of CH_4 and H_2O over MoO_3-TiO_2/SiO_2 catalyst at 150℃ in a fixed-bed annular photoreactor,and the CH_3OH selectivity is 87.3%.