Studies On Efficitent Synthesis Of O-nitrobenzoic Acid From O-nitrotoluene Catalyzed By Metalloporphyrin-meallic Salts

o-Nitrobenzoic acid is an important intermediate wildly used in medicines, dyes,photographic materials and other fine chemical intermediates. Traditional synthesismethods of o-nitrobenzoic acid such as oxidation with sodium hypochlorite havemang disadvantages including serious equipment corrosion, serious environmentalpollution and so on. As a novel biomimetic catalyst metalloporphyrin has advantagesof low amount of catalyst, high turnover number and environmentally friendlyadvantages, which attracts the attention of many scientists. Oxidation ofo-nitrobenzoic acid from o-nitrotoluene by metalporphyrin has been studied by ourteam with a yield of up to76.3%. However, this method still has some disadvantagessuch as a low yield, imperfect catalytic system, a larger amount of alkali, a longerreaction time. Therefore, this method also needs to be improved from enhancingsynthesis yield, improving catalytic system, reducing the amount of alkali, reducingreaction time and other aspects of research.To solve the above problems, efficient synthesis of o-nitrobenzoic acid fromo-nitrotoluene catalyzed by metalporphyrin-metallic salts was studied. First of all,catalytic properties of metalporphyrin-metallic salts composite catalysts andmetalporphyrin-metalporphyrin composite catalysts were studied. Meanwhile,catalytic properties of single metalporphyrin and single metallic salts were campared.Moreover, differences of catalytic properties of single catalysts and compositecatalysts were researched systematically. Also the amount of catalysts, the compositeratio and the reaction conditions were researched deeply. The results showed thatT(p-Cl)PPCoCl-Mn(OAc)2·4H2O had better catalytic activity. The results also showedthat the amount of catalysts and the composite ratio had great impacts on catalyticproperties of catalysts. And catalytic properties of composite catalysts was betterwhen the amount of catalysts was1.0×10-5mol/L and the composite ratio was1:1.Compared with the reaction conditions our team optimized before, the reaction timewas shortened to6h from12h, the concentration of NaOH was minished to2.5mol/L from3.75mol/L, but the yield of o-nitrobenzoic acid was increased to87.8%from76.3%, indicating that composite catalysts exhibited better catalytic propertiesthan the single metalporphyrin in this reaction.Then the apparent kinetics of aerobic oxidation of o-nitrotoluene too-nitrobenzoic acid with T(p-Cl)PPCoCl-Mn(OAc)2·4H2O was investigated. By determining the experimental data at different temperatures the apparent rate constantswere calculated, which showed that the first step for oxidation of o-nitrotoluene intoo-nitrobenzaldehyde was a first-order reaction with an apparent activation energy of75.94kJ/mol, and the second step for oxidation of o-nitrobenzaldehyde intoo-nitrobenzoic acid was a half-order reaction with an apparent activation energy of36.22kJ/mol. Compared with the first and the second step of the reaction apparentactivation energy with metalloporphyrin catalyst (104.93kJ/mol and56.09kJ/molrespectively), composite catalyst system can significantly reduce the apparentactivation energy of the above reaction by28.99kJ/mol and19.87kJ/mol respectivelyin the first and the second step. Moreover, it explained the reason why compositecatalyst was more active than the separate metalporphyrin from dynamics, which isthe synergic action between metalporphyrin and metallic salts.