Preparation And Application Of Selenium-doped Polymeric Carbon Nitride Photocatalysts

Photocatalysis is a vital point in chemical process design.As an interesting material within the field of photocatalysts,PCN(polymeric carbon nitride)has great obvious visible light activity,reasonable band structure,good tunability,thermal stability and chemical stability.PCN can oxidize holes to form H2O2 under visible light irridiation,which can be used in the photocatalytic transformation of organic functional groups and the photocatalytic degradation of organic pollutants.As a dispersed element,selenium has good chemical properties and biological activity.Selenide catalyst has the function of carrying oxygen and can catalyze the oxidation reaction with H2O2 as oxidant,which is widely used in organic synthesis,biochemistry and materials science.Inspired by the above characteristics of PCN photocatalyst and selenium catalysis,in this thesis,we developed a new method of relay catalysis of PCN and selenium,and synthesized two kinds of PCN photocatalysts such as PCN-Se and PCN-Se-glu.They were applied in some promising industrial reactions such as the synthesis of,β-ionone epoxides in fine chemical industry,the deoxime reaction of carbonyl protection process and the degradation of aldehydes in VOCs waste gas treatment,and the related process routes are discussed.The specific research contents are as follows:1.PCN-Se photocatalyst was synthesized by thermal polymerization and applied to the synthesis of β-ionone epoxide,a fine chemical product.The effects of the amount of selenium in PCN-Se catalyst,the used amount of PCN-Se catalyst,solvent and reaction time on the reaction were investigated.It was found that the mixture of alcohol and water as solvent could improve the reaction efficiency.Finally,the yield of β-ionone epoxide was 50%,and the conversion of β-ionone was 82%.The stability of PCN-Se was also investigated.After five cycles,the conversion of β-ionone,the yield of epoxide and the selectivity of the reaction did not decrease significantly.The catalyst was characterized and the reaction mechanism was discussed.2.In view of the excellent photocatalytic performance and stability of the previous part of PCN-Se photocatalyst,we tried to apply PCN-Se photocatalyst on deoximation reaction,which was one of the significant carbonyl protection processes.The effects of the amount of PCN-Se catalyst,the solvent of reaction and reaction time on the reaction were investigated.PCN-Se photocatalyst did not show high catalytic activity in the deoximation reaction.However,we unexpectedly found that the deoximation reaction driven by visible light was actually an autocatalytic process,and the yield of benzophenone is 86%under specific conditions,which was applicable for some ketoxime compounds.The possible reaction mechanism was also discussed.3.A novel porous selenium and carbon co-doped carbon nitride photocatalyst PCN-Se-glu,was synthesized by thermal polymerization and applied to the degradation of acetaldehyde in VOCs waste gas to evaluate its photocatalytic activity.The final degradation rate of acetaldehyde gas was 87%in 13 hours.The performance of PCN-Se-glu photocatalyst was systematically characterized and described from the aspects of morphology,structure,crystal state,chemical state and photoelectric effect of PCN-Se-glu photocatalyst.