Study On Preparation Ofsupported Silvercatalysts And Their Photocatalytic Performance

Ag/TiO2and Ag/SiO2photocatalysts were prepared through colloidal adsorption method and sol-gel method in this paper. In order to study their photocatalytic performance on methy formate formation from methanol and cyclohexane oxidation by oxyhen, the catalysts were investigated and tested systematically at the room temperature and under the ultraviolet irradiation.Firstly, using P25and commercial SiO2as supports, the Ag supported catalysts were prepared by colloidal adsorption method and sol-gel method, and were characterized by XRD、 TPR、 TEM and UV-Vis DRS in order to obtain the structures and crystal phases. The results show that the two kinds of catalysts were in a good dispersion and no obviously gathered phenomenon with an almostly uniform particle size, in which nano-Ag existed as a simple substance. And the photoadsorption of these catalysts was improved after nano-Ag loaded.Secondly, the two kinds of catalysts were used in the reaction of methyl formate photocatalytic production form methanol. It is found that the catalyst with5%Ag over P25prepared by colloidal adsorption method had the best photocatalytic performance, and the methyl formate formation mete could reached to 12783μmol/g/h. While the catalyst with3%Ag on SiO2, the methyl formate formation mete could attain to23459μmol/g/h. However, when the catalysts were prepared by a sol-gel method using CTAB as a dispersion agent, the optimum methyl formate formation mete reached to17424μmol/g/h for the2%Ag loading catalyst.Thirdly, the two kinds of catalysts were used in the reaction of cyclohexane photocatalytic oxidation. It is found that the1%Ag/TiO2prepared through colloidal adsorption method had a high cyclohexane conversion, but a mild total selectivity of alcohol and ketone and the alcohol/ketone ratio. The3%Ag/TiO2showed the highest alcohol/ketone ratio. The5%Ag/TiO2showed the highest total selectivities of alcohol and ketone. The conversion of cyclohexane increased over the3%Ag/SiO2catalysts. As for Ag/TiO2photocatalysts prepared through sol-gel method, the3%Ag/TiO2photocatalysts showed a high total selectivities of alcohol and ketone and the alcohol/ketone ratio as well. The5%Ag/TiO2photocatalysts had a good conversion of cyclohexane, but a mild alcohol/ketone ratio.