Study On Vanadium-based Catalysts Via Ionic Liquid-assisted Thermal Synthesis And Study On Catalytic Performance

Phenol is an important organic product in petrochemical production.It plays an important role as a raw material or solvent in the manufacture of dyes,synthetic resins,plastics,synthetic fibers,and pesticides.At the same time,it also plays an important role in industrial and agricultural production,national defense,and medicine.Currently,there were many production methods for phenol in industry,and the mainstream preparation method was the cumene method.However,its preparation process was lengthy and produced by-products such as acetone,which was not in line with the current concept of green chemistry.At the same time,according to atomic economy,the hydroxylation of benzene to phenol was undoubtedly the most satisfying preparation method for converting 100%of the atoms in the raw material molecule into products without generating by-products or wastes.Using hydrogen peroxide as an oxidant,the by-product of hydroxylation of benzene to phenol was only water,which not only had the advantages of high atomic utilization,but also had the advantages of short process and environmental friendliness.The research of phenol by benzene hydroxylation has great potential and profound significance In this paper,vanadium metal is mainly used as the active site of the catalyst to prepare vanadium based catalysts with uniformly dispersed active sites,adjust and optimize the preparation method of the catalyst,regulate the uniform dispersion of the active site,where will improve the catalytic performance and stability of the catalyst,and optimize the reaction conditions to achieve the purpose of obtaining a higher benzene conversion rate and a higher selectivity of phenol.The content of this study is as follows:（1）Al₂O₃ carrier was synthesized using ionic liquid[Bmim]Br and dipropylamine as a template.VO_x/Al₂O₃ catalyst was prepared by hydrothermal method by loading vanadium pentoxide onto Al₂O₃.The catalytic effect was verified in the reaction of benzene hydroxylation to phenol.The results show that the catalysts have a large specific surface area and the vanadium active sites are uniformly distributed on the surface of the catalysts.When H₂O₂ was used as oxidant and acetonitrile as solvent,the conversion rate of benzene was 36.3%and the selectivity of phenol was 86.2%.（2）Based on the Al₂O₃ support synthesized using ionic liquid[Bmim]Br and dipropylamine as a template,and adding phosphoric acid as a phosphorus source,an Al PO₄ support can be obtained.VO_x/Al PO₄ catalyst was prepared by hydrothermal method by loading vanadium pentoxide onto Al PO₄,which was used to catalyze the hydroxylation of benzene to phenol.The catalytic performance of the catalyst was tested and found to have high catalytic activity and good phenol selectivity,The main reason is that the P element on the catalyst carrier regulates the acidity of the catalyst,creating a slightly acidic environment conducive to the reaction.Through optimization of reaction conditions,the conversion of benzene was 53.4%,and the selectivity of phenol was 98.4%.（3）Based on the Al₂O₃ support synthesized using ionic liquid[Bmim]Br and dipropylamine as a template,and adding phosphoric acid and tetrabutyl titanate simultaneously,a Ti O₂-Al PO₄ composite support can be obtained.A series of VO_x/Ti O₂-Al PO₄ catalysts were prepared by hydrothermal method by loading vanadium pentoxide onto the Ti O₂-Al PO₄ support.After conducting experiments on the hydroxylation of benzene,it was found that it had the highest benzene conversion rate and higher phenol selectivity,The interaction between Ti and V enhances the electron and spin motions in vanadium oxides,and Ti species research polarizes the C-H bond on the benzene ring,making the reaction easier to proceed.After optimizing the reaction conditions,its benzene conversion rate reaches 62.3%and phenol selectivity reaches 97.9%.