Vanadium-based Catalyst In The Application Of Hydroxylation Of Benzene

Phenol is a significant intermediate for the manufacture of many chemicals in industry,and widely used in the fields of resins,fibers and medicines.In recent years,much attention has been paid to developing mild and environment-friendly routes to more effectively produce phenol.Consequently,it is desired to develop direct hydroxylation of benzene to phenol.This topic selects vanadium as the active centre,and applies the metits of hydrothermal synthesis method to improve the catalytic activity and the stability of catalyst.The finally aim is to optimize the reaction condition and to improve vanadium-based catalyst.?1?The V_xO_y@C catalyst is prepared from VO?acac?₂ and glucose by a one-pot hydrother-mal synthesis,and it is investigated and characterized by XRD,FT-IR,SEM,TEM,BET,EPR and DR UV-vis etc.The catalyst is carbon microsphere,its diameter is 2?m¹0?m.The specific surface area?the pore volume?the pore width of the catalyst are vary small.The valence state of vanadium of the catalyst is tetravalent and pentavalent.The heterogenous solid-liquid-phase direct catalytic oxidation of benzene to phenol is performed in acetic acid solvent and oxygen gas as the oxidant.The effects of various preparation factors?reaction parameters and precursors,such as the species and quality of the precursor,hydrothermal synthesis temperature,hydrothermal synthesis time,reaction temperature,reaction time etc,are studied.Under the optimized preparation and reaction parameters,the V_xO_y@C?N?catalyst exhibited good catalytic activity,but can not be reused.The catalytic activity of V_xO_y@C?A?is also high and the stability of V_xO_y@C?A?is quite well.?2?The C/V/SiO2 catalyst is prepared from V/SiO2 and glucose by hydrothermal synthesis and argon roating method.The characteristic of the C/V/SiO2 catalyst are studied by XRD,FT-IR,SEM,TEM,BET,EPR and DR UV-vis etc.The C/V/SiO₂ catalyst is covered by a large number of carbon?the diameter is 20nm⁵0nm?,The specific surface area of C/V/SiO₂ is smaller than that of V/SiO₂,but the pore volume?the pore width of C/V/SiO₂ is bigger.And the valence state of vanadium are trtravalent and pentavalent.The reaction is performed in acetic acid solvent and the oxygen as the oxidant.The study investigates not only the parameter of preparation and reaction,but also the stability of the catalyst.Under the optimized reaction condition,the stability of V/SiO₂ catalyst is inferior.However,the C/V/SiO₂ catalyst was reused three times;the benzene conversion and phenol selectivity is always stable.