Preparation of phthalimide by ammoxidation of o-xylene and characterization of V-Cr-O/SiO_2 catalyst

摘要

Phthalimide,as an important intermediate of organic synthesis,has been prepared with high yield by amoxidation of o-xylene over silica-supported vandium-chromium oxide catalysts.Under suitableconditions,the molar yield of phthalimide can reach 89% with purity of 98.6%.The catalysts,prepared via wet-impregnation method,have b een characterized by BET,XPS and SRD.Results show that vanadia and chromiaform composite oxides,which exist mostly in the pores of silica.Their concerted catalytic function is the main reason for high activity.Vanadium exists mainly as pentavalent and chromium mainly as trivalent in the V-Cr-O/SiO_2 catalysts,whith their oxidation states changing in the redox cycles.The additive chromium can interact with the surface vandium oxide phase and alter the structure of vanadia,which delyas the formation of crystalline V_2O_5 and increases the catalytic activity and selectivity.