Preparation Of C₃N₄ Based Composite And Study On Selective Oxidation Of Benzyl Alcohol In Aqueous Solution

With the rapid and good development of the economy,the problem of environmental pollution isbecoming more and more serious since the twentieth century.With the increasing demand for the quality of life and environment as well as the stream of environmental pollution problems,scientists hope to develop environmental friendly,low energy organic synthesis technology,and benzyl alcohol selective oxidation to benzaldehyde is an important part of organic synthesis,which is of great importance in academic laboratory and industry.Therefore,the development of environment-friendly organic synthesis technology is becoming more and more popular by scientists.In the field of alcohol selective oxidation,graphite phase carbon nitride（g-C₃N₄）,as a new type of metal free catalyst,has the advantages of simple synthesis method,cheap raw materials,low toxicity,good thermal and chemical stability.However,g-C₃N₄ has low catalytic activity because of its large particle diameter,low specific surface area,High recombination rate of photogenerated electron hole and narrow absorption range in the visible region.At present,many scientists modify them in three ways:（1）Recombination with other semiconductor materials to form heterojunction to inhibit the recombination of photogenerated electron holes.（2）Morphological modification to change the specific surface area.（3）Doping with other elements to improve the range of absorption of visible light.In this study,g-C₃N₄ was prepared by calcination,and AgPd/g-C₃N₄ composite was prepared by sodium borohydride reduction method.The conversion and selectivity of benzyl alcohol to benzaldehyde in aqueous solution were improved.The main contents and results are as follows:（1）.Preparation of g-C₃N₄ and study of selective oxidation of benzyl alcoholg-C₃N₄ was prepared by calcination with cyanoguanidine as precursor.The sample werecharacterized by X ray diffraction（XRD）,field emission scanning electron microscopy（FE-SEM）,transmission electron microscopy（TEM）,electron spin resonance（ESR）and UV-vis diffuse reflectance spectroscopy（UV-vis DRS）.The effect of different reaction conditions on the selective oxidation of benzyl alcohol was studied,the results showed that the selectivity of benzaldehyde reached 86.7%under the irradiation of LED lamp,room temperature and 5 mL diethyl ether.The use of free radical scavengers showed that O^2·-,OH^·and h⁺are the main active species for the selective oxidation of benzyl alcohol to benzaldehyde.（2）.Preparation of AgPd/g-C₃N₄ composite and study of selective oxidation of benzyl alcoholAg/g-C₃N₄、Pd/g-C₃N₄和AgPd/g-C₃N₄ was prepared by using sodium borohydride as reductant.The samples were characterized by X ray diffraction（XRD）,high resolution transmission electron microscopy（HR-TEM）,UV-vis diffuse reflectance spectroscopy（UV-vis DRS）and X ray photoelectron spectroscopy（XPS）.The effect of the load of silver and palladium nanaoparticles on the selective oxidation activity of benzyl alcohol was studied,the results show that silver and palladium nanoparticles are successfully loaded on the surface of g-C₃N₄,and silver and palladium nanoparticles can reduce the recombination probability of photo generated electrons and holes,thereby enhancing the catalytic activity.