Photocatalytic Oxidation Of Cyclohexane And α-Pinene By Transition Metal Vanadate

Photochemistry is one of the most popular international frontier research fields in recent years,which is widely used in sewage treatment,solar energy conversion and photoelectric conversion and so on.Compared with the traditional thermal reaction,photochemical synthesis uses light as a kind of clean energy source,which has the advatanges of milder activation conditions,faster reaction speed and fewer side reactions.It is a new synthetic method,which has gained much attention in the past decade.The main work of this thesis is to study the catalytic activity and regulation on the product selectivity of cyclohexane、a-pinene and cyclohexene through metal vanadate photocatalytic oxidation.The effects of catalyst,solvent,time and additive in the oxidation reaction were carefully investigated.At the same time,the structure-function correlation of the catalyst band and the electron density of the active sites had also described by UV-Vis,XRD,XPS characterization methods and theoreticed chemical calculations.The main contents are as follows:(1)A series of transition metal vanadate materials were prepared by precipitation method for the 02 oxidation of cyclohexane to prepare KA oil(cyclohexanol and cyclohexanone).BiV04 can promote the oxidation of cyclohexane under the visible light irradiation.The conversion frequency(TOF)based on V active site could reach to 7.44 h-1 and the high selectivity of KA oil was 95.07%.Moreover,Cu3V2O8 promote the selectivity of chlorocyclohexane intermediates was 45.77%.To explain this interesting phenomenon,the optical properties,electronic structures and Energy level band of BiYO4 and Cu3V2O8 were analyzed by density functional theory(DFT).Found that the electronic transition of BiV04 is a direct transition,the band gap energy is about 2.34 eV and a conduction band bottom composed of Bi3+6p and V5+3d states.The electronic transition of Cu3V2O8 is an indirect transition,and the band gap energy is about 1.83 eV,V5+3d and Cu2+ 3d state compositions conduction band bottom.Compared with Cu3V2O8,BiVO4 with more P characteristics can accelerate the efficient transfer of charge carriers and promote the oxidation of cyclohexane by the production of active substances such as·OH,h+and H202 during illumination.(2)Metal copper vanadate was applied to an olefin oxidation experiment using a-pinene and cyclohexene as models.The effects of the vanadium structure changes at different calcined temperatures on the catalytic activity were carefully investigated.The results show that the calcination temperature can regulate the photocatalytic activity of the catalyst:The conversion rate of a-pinene by uncalcined catalyst was 9.71%.The conversion rate of a-pinene by 400℃ catalyst increased to 33.75%,when the temperature increased to 700℃,the conversion rate decreased to 15.79%.FT-IR,UV-Vis DRS,Raman,XRD,XPS and TEM spectroscopy were used to confirm the structure of the catalyst.With the increase of calcination temperature,the structure of copper vanadate is changed by Cu3(V2O7)(OH)2·2(H2O)→Cu3V2O8→Cu3V2O7,and the coordination mode of the corresponding metal atom changes the active point structure and band energy.It was also found that vanadate has good catalytic activity for cyclohexene of similar structure.With Cu3V2O8 as catalyst and acetonitrile as solvent,the reaction rate of cyclohexene reached 26.79%and the total selectivity of cyclohexenol and cyclohexenone reached 94.27%.