Study On The Photocatalysis Of Nano-Gold Catalysts

As a kind of environmentally friendly energy, light can activate reagent molecules (or catalyst) under mild conditions, promote the reactions, and thus improve the conversion of reactants and selectivity of products. Studies in recent years have shown that noble metal nanoparticles have good absorption of ultraviolet and visible light, and can selectively catalyze reactions under mild conditions, which has become hot topics of the new photocatalystsIn this paper, the photocatalytic performance of supported nano-gold catalysts were investigated for selective oxidation of methanol to methyl formate and cyclohexane to cyclohexanol and cyclohexanone. Then the photocatalytic reaction mechanisms of different gold catalysts in corresponding reactions were discussed. The research details and main conclusions are as following.1. Supported nano-gold catalysts were prepared by metal-sol deposition method and characterized by XRD, TEM, UV-Vis, ICP. The results indicated that the particles size of gold was3-8nm, and was well dispersed on the support. Also supported nano-gold catalysts exhibited a strong absorption in visible light band because of the Surface Plasmon Resonance (SPR) effect under visible irradiation.2. The oxidative dehydrogenation of methanol to methyl formate was carried out under normal pressure and temperature. The results of blank experiment show that the reaction can not occur in the dark or without oxygen. The catalytic activity of different catalysts under normal pressure and temperature with ultraviolet irradiation was also investigated. The3%Au/ZrO2catalyst prepared by metal-sol deposition method had great catalytic activity, with the highest MF formation rate of27602.78μmol/g/h.3. The selective oxidation of cyclohexane was carried out under the conditions of normal pressure and temperature and light irradiation. For Au/ZrO2and Au/TiO2catalysts, the target products were cyclohexanol and cyclohexanone. Under the mercury lamp illumination, and with O2as the oxidant, acetonitrile as solvent, and TBHP as initiator, the conversion of cyclohexane was10.44%, and the total selection of cyclohexanol and cyclohexanone was more than98%.4. The reaction mechanism of methanol selective oxidation is briefly discussed. Under ultraviolet irradiation, the electrons on the surface of nano-gold particles were induced to transit between interbands and became high energy electrons then the reaction occurred.