Construction Of TiO₂ Based Heterojunction Composite Catalyst And Study On Its Photocatalytic Performance For The Preparation Of Benzaldehyde From Benzyl Alcohol

In recent years,energy and environmental issues have attracted much attention,and the development of sustainable clean energy and environmental protection technology to solve the depletion of fossil fuels and the increasingly serious environmental pollution has become the focus of research in the field of chemical industry,especially in the field of catalysis.The selective oxidation of alcohols to produce corresponding aldehydes is of great significance to the sustainable development of the chemical industry.Benzaldehyde is widely used in raw materials and intermediates such as medicine,perfume and dyes,and is an important raw material of industrial chemicals.The traditional methods of industrial synthesis of benzaldehyde are oxidation of toluene or hydrolysis of benzyl chloride,in which a large number of harmful reagents are used and a large number of toxic by-products are generated.Therefore,it is urgent to find a safe,green and environmentally friendly benzaldehyde synthesis route.The photocatalytic selective oxidation of benzyl alcohol to benzaldehyde has been extensively studied in recent years.Photocatalytic oxidation,with its green,energy saving and pollution-free characteristics,has shown great advantages and considerable prospects in the selective oxidation of benzyl alcohol to benzaldehyde,and is regarded as one of the most promising strategies to solve energy and environmental problems in the future.Photocatalytic oxidation technology can realize the conversion of benzyl alcohol to benzaldehyde at low temperature,because the reaction is carried out at low temperature,the byproducts are less.Therefore,it is of great significance both in theory and in practice.However,the current catalysts used for such photocatalytic reactions have a narrow light absorption range,low separation efficiency of photogenerated charges,and generally low photocatalytic efficiency,which limits their practical application.Based on the above analysis,the specific research content of this paper is as follows:1.Using sodium titanate nanotubes as precursor,the In VO₄/TiO₂heterojunction composite photocatalyst was successfully constructed by hydrothermal method.In the hydrothermal reaction process,sodium titanate nanotubes were dissociated and self-assembled to form TiO₂,while In VO₄nanoparticles grew on the surface of TiO₂,effectively constructing heterojunctions.At the same time,the morphology composition and chemical structure of the catalyst were further analyzed.The results showed that the In VO₄（112）crystal surface and TiO₂（101）crystal surface were in close contact,forming heterojunction,promoting the separation and transport of photogenerated carriers,speeding up the reaction kinetics,and improving the photocatalytic activity.In the photocatalytic oxidation of benzyl alcohol to benzaldehyde,After reaction at 60℃for 3h,the conversion rate is 100%,and the selectivity of benzaldehyde can reach 100%.2.2D/2D g-C₃N₄/TiO₂heterojunction micron flower was constructed by a method of in-situ stripping and self-assembly.The close face-to-face contact between g-C₃N₄nanosheets and TiO₂（B）nanosheets effectively constructed the inner boundary electric field,promoted the transfer of electrons from g-C₃N₄guide band to TiO₂（B）guide band,and improved the separation efficiency of photogenerated charge carriers.Moreover,the g-C₃N₄/TiO₂（B）composite catalyst showed excellent photocatalytic performance for the preparation of benzaldehyde from benzyl alcohol under the reaction temperature of 60℃and light irradiation.The conversion and selectivity of CNT-0.14 were close to 100%after 4 h reaction,and the formation rate of benzaldehyde reached 1.15 mmol·g^-1·h^-1.3.Au nanoparticles were deposited on the surface of 2D/2D TiO₂（B）/C₃N₄catalyst by photoreduction method,and the Au-TiO₂-C₃N₄ternary heterojunction composite catalyst was controllable constructed.The surface plasmonic resonance effect of Au enhances the electron coupling and interfacial synergism,and promotes the separation and transport of photogenerated carriers.It shows enhanced photocatalytic performance in the photocatalytic synthesis of benzyl alcohol to benzaldehyde,and the generation rate is 5.6 and 8.3 times that of Au-TiO₂and TiO₂-C₃N₄,respectively.