Catalytic Oxidation Of 2-Methylnaphthalene By Hydrogen Peroxide

As an important fine chemical raw material,β-menadione is widely used in medicine,pesticides,feed additives and other fields.At present,β-menadione is mainly synthesized by catalytic oxidation of 2-methylnaphthalene with chromic anhydride,and the synthesis process has large consumption and serious pollution.Therefore,in this paper,hydrogen peroxide was used as the oxidant with 30%mass fraction.The V₂O₅/g-C₃N₄ catalyst and hydrogen peroxide-acetic acid system were used to catalyze the oxidation of 2-methylnaphthalene toβ-menadione,respectively.In the acetonitrile system,V₂O₅/g-C₃N₄ was used as catalyst to catalyze the oxidation of 2-methylnaphthalene with hydrogen peroxide.The effects of substrate concentration,reaction time,reaction temperature and reaction time on the synthesis ofβ-menadione were investigated by single factor.The optimized conditions for the synthesis ofβ-menadione were determined:2-methylnaphthalene 0.2 g;reaction temperature 80℃;reaction time 1 h;hydrogen peroxide 3 mL（mass fraction 30%）;catalyst dosage 0.03 g.Under the optimum conditions,the conversion of2-methylnaphthalene was 39.33%,and the selectivity ofβ-menadione was 27.21%.Through a regression orthogonal design,the effects of oxidant dosage,reaction time and reaction temperature on conversion and selectivity were investigated.The regression equation and primary and secondary factors were determined,and The results showed that the experimental data were well fitted by the equation.The oxidation effect of 2-methylnaphthalene in the hydrogen peroxide-acetic acid system was investigated without adding a catalyst.Through the investigation of single factor,the optimal reaction conditions were obtained:2-methylnaphthalene0.4 g,reaction temperature 90℃,reaction time 3 h,hydrogen peroxide 3 mL（mass fraction 30%）,acetic acid 10 mL.Under the optimum conditions,the conversion of2-methylnaphthalene was 90.18%,and the selectivity ofβ-menadione was 35.81%.The critical temperature,critical pressure and the standard heat of formation,standard entropy and specific heat of oxidation for 2-methylnaphthalene andβ-menadione were estimated by the group contribution method;thermodynamic data such as standard reaction enthalpy change,entropy change,Gibbs free energy change and equilibrium constant were calculated.The results show that the oxidation reaction of 2-methylnaphthalene is a strong exothermic reaction at 313.15³93.15 K.The Gibbs free energy is negative and the equilibrium constant is 1.06¹.08×10³.The effect of temperature on the thermodynamic function was discussed in detail.