Selective Oxidation Of Alcohols Over Modified Titanate

Selective oxidation of alcohols to carbonyl compounds is of great significance for organic synthesis and organic conversion since aldehydes and ketones are raw materials for the synthesis of pharmaceuticals,pesticides and other miscellaneous chemicals.There exists a sea of disadvantages in the traditional alcohol oxidation reactions in industry,involving requiring a certain stoichiometric ratio of oxidants such as potassium permanganate,potassium dichromate,hydrogen peroxide,etc.,which is likely to cause secondary pollution,and demanding high temperature and high pressure that consumes a few more energy.Compared with the traditional thermal catalytic oxidation method,the photocatalytic oxidation technology has attracted extensive attention as it is with excellence of low energy consumption,mild reaction conditions,and green pollution-free characteristics.According to the different reaction conditions,the application of photocatalytic alcohol selective oxidation basically includes two aspects:1.Under aerobic conditions,alcohol is oxidized to aldehydes and produce water with oxygen as the oxidant.2.Under anaerobic conditions,alcohol undergoes dehydrogenation to produce the corresponding carbonyl compounds and H2,which is universally considered a clean energy.Nevertheless,the current photocatalytic alcohol selective oxidation system mainly has the following issues:1.The selectivity and conversion are relatively low.2.It needs to be carried out in organic solvents.Perovskite semiconductor materials,titanate(SrTiO3)are widely applied in photocatalytic reactions which attributed to their favorable chemical stability and photoelectric properties.However,SrTiO3 need to be modified to achieve highly selective and efficient photocatalytic oxidation of alcohol owing to the high photo-generated electron-hole recombination rate and merely response to ultraviolet light.The introduction of oxygen vacancies and doping energy levels through metal or nonmetal doping is an effectual approach to achieve visible light or even near-infrared light response and reduce the recombination rate of photo-generated carriers.Based on the above problems and the modification strategies of perovskite titanate,in this paper,we synthesized copper-doped SrTiO3(Cu-STO),which was employed in photocatalytic selective oxidation of alcohols under visible light and even near-infrared light,for the first time via the modified polymerized complex method.A series of characterization methods was carried out to analyze the properties and performances of Cu-STO.The results indicated that oxygen vacancies and doping energy level have been introduced by copper doping,thus reducing the band gap of the STO,and the light response range was extended to visible light and even near-infrared light.Moreover,the transfer rate of photo-induced electron-hole pairs was improved.and the recombination rate of photo-generated carriers was reduced simultaneously.By changing the calcination temperature,the amount of Cu doping and the amount of Pt loading,the performance of selective oxidation of benzyl alcohol under visible light and near-infrared light was further improved.Subsequently,the general applicability and satisfying stability of Cu-STO to other alcohols was proved.At last the performance of Cu-STO under aerobic conditions and anaerobic conditions were explored respectively,in addition,the main active species in two conditions was investigated by radical capture experiment and in-situ EPR to illustrate the reason for the performance difference.On this basis,we further the catalytic oxidation process of 1,2-benzenedimethanol.Compared with different metal oxide catalysts,we discovered that the nano-BaTiO3(BTO)prepared by polymerized complex method have better catalytic performance.The morphology,particle size and specific surface area of Pt loaded BTO were obtained by TEM and BET.The lattice spacing of Pt nanoparticles and BTO was obtained by HRTEM.By adjusting the amount of BTO,calcination temperature and Pt loading amount,the effects of different factors on the catalytic performance were explored.The results of dark reaction experiments show that the oxidation of 1,2-benzenedimethanol on BTO is not only due to the photocatalytic results,but also the thermal catalysis can cause good reaction activity.The specific effect of visible light and thermal needs further study.