Preparation,Characterization And Performance Of Simulated Sunlight Response Catalysts For Methyl Formate Synthesis From Methanol

Photocatalytic selective oxidation of methanol to methyl formate?MF?is a new green production process,but ultraviolet light is commonly employed in most of the current researches,resulting in a low light utilization rate.It is thus of certain scientific significance and practical application potential to study photocatalytic oxidation of methanol to methyl formate using simulated sunlight as light source.Three series of N-TiO₂ and Zr-TiO₂ based photocatalysts and core-shell Ag@N?Zr?-TiO₂ catalysts were prepared by wet chemical method.The morphology,surface properties and elemental states of the catalysts were characterized.The selective oxidation of methanol to methyl formate by the catalysts was investigated under the irradiation of a xenon lamp with the feed gas flow rate of 10 ml/min at the temperature range of 25-45?.The reaction mechanism was preliminarily speculated.The results are as follows.1.The morphologies of the three kinds of N-TiO₂ catalysts prepared by using ammonia,urea and ammonium chloride were remarkably different.N atoms were interstitially doped in the lattice of TiO₂.And impurity levels were formed between the valence band and the conduction band of TiO₂.A red shift of the absorption edge was observed,and the specific surface area increased,as well as the number of surface hydroxyl groups and nitrogen-containing species.The catalyst prepared by using ammonium chloride exhibited the best photocatalytic activity.2.The catalytic performance of the core-shell Ag@N-TiO₂ catalyst was remarkably influenced by the Ag content,thickness of the shell as well as the calcination temperature.The optimum preparation conditions were 3 ml of AgNO₃ solution,7mmol of TBOT and 500°C of the calcination temperature.Ag was conductive to the separation of the photoexcited electron-hole pair and thus increase the selectivity of methyl formate.3.As for Zr-TiO₂,Zr⁴⁺replaced a small amount of Ti⁴⁺to form the lattice of TiO₂.The doping of Zr inhibited the growth of the TiO₂ crystal and resulted in the decrease of the band gap of the catalyst and the increase of the number of surface hydroxyl groups,which was beneficial to the formation of methyl formate.The morphology,element composition and photocatalytic activity of Zr-TiO₂ catalyst prepared by different zirconium precursor were different,while Ag had not significant influence on the photocatalytic activity of the catalyst.