Study On The Photocatalytic Performance Of Noble Metal Supported TiO₂ On Dehydrogenation Of Methanol To Methyl Formate

The photocatalytic dehydrogenation of methanol to methyl formate is a new green route.It is of certain scientific significance and practical application potential.In this study,Au/TiO₂,Ag/TiO₂ and Cu/TiO₂ catalysts were prepared.The phase,band structure,surface species,morphology,specific surface area and element valence of the catalyst were characterized by X-ray diffraction?XRD?,solid ultraviolet-visible diffuse reflectance?UV-Vis?,Fourier transform infrared spectroscopy?FTIR?,transmission electron microscopy?TEM?,N₂ adsorption and desorption and X-ray photoelectron spectroscopy?XPS?.The photocatalytic activity of the catalyst for the dehydrogenation of methanol was investigated under the irradiation of ultraviolet light at the reaction temperature range of 25-45°C with the feed gas composition of 99%N₂ and 1%methanol.The preliminarily reaction mechanism was proposed.The research contents and results are as follows:1?For the Au/TiO₂ and Ag/TiO₂ catalysts,Au dispersed on the surface of TiO₂ in metallic state,while the Ag/TiO₂ catalyst contained metallic Ag and a small amount of monovalent Ag.The photocatalytic activity of the catalyst loading with the noble metal was significantly increased,and main the products were methyl formate,a small amount of H₂.The catalyst of 3%Au/TiO₂ and 3%Ag/TiO₂ exhibited the best photocatalytic activity.With the increase of the feed gas flow rate,the methanol conversion rate and the selectivity of methyl formate gradually decreased.With the enhancement of light intensity,the methanol conversion rate and the selectivity of methyl formate gradually increased.2?For the catalyst of Cu/TiO₂,copper species mainly existed in the form of Cu²⁺on the surface of TiO₂.The main products were methyl formate,a small amount of H₂and C₂H₄.The photocatalytic activity of Cu/TiO₂ with 5%Cu content exhibited the best photocatalytic activity.The methanol conversion rate reached 29%,the methyl formate selectivity was 76%,the MF formation rate was 2.39 mmol/g/h,and the hydrogen yield was 0.3%.The methanol conversion rate reached the maximum at the gas flow rate of 20 mL/min,and the methyl formate selectivity was 77%at the flow rate of 40 mL/min.As the light intensity increased,the photocatalytic activity gradually increased.3?By trapping electrons,the noble metal effectively reduced the recombination of photogenerated electrons and holes,and thus improving photocatalytic activity.