Studies On The Co-catalysis Of Metalloporphyrin And Cobalt Acetate In The Aerobic Oxidation Of P-Xylene

Metalloporphyrin and metalloporphyrin-cobalt acetate catalyzed liquid phase oxidation of p-xylene with air is studied in this dissertation. The effects of the catalysts and reaction conditions on the catalysis of metalloporphyrin and cobalt acetate are investigated and a new route of p-xylene oxidation is proposed.Liquid phase oxidation of hydrocarbons with air is a very important reaction in chemical industry. For example, about 30 million tons of terephthalic acids are produced annually by oxidation of p-xylene with air.Firstly, the basic concepts and recent advances in the field of hydrocarbon oxidation are summarized, and the process and mechanism of hydrocarbon oxidation are discussed. The achievements and the problems in this subject are pointed out. Also the brief introduction of metalloporphyrin catalyzed hydrocarbon oxidation is presented.Secondly, a new HPLC method to quantitatively analyze the oxidation products of p-xylene is developed and optimized. The method is rapid, accurate and reproducible.Thirdly, the aerobic liquid phase oxidation of p-xylene over metalloporphyrin is carried out. The effects of solvent, catalysts and reaction conditions are investigated. Acetic acid is fine solvent in metalloporphyrin catalyzed p-xylene oxidation, and its concentration should be limited to a relatively low level. T(p-Cl)PPMnCl is the appropriate catalyst for this reaction with the highest p-xylene conversion and p-toluic acid and terephthalic acid yields. Also the formation and transformation of the intermediate products in this reaction, and their influence on the whole reaction are studied. The metalloporphyrin catalyzed oxidation of p-xylene has the advantage of mild condition, low catalysts loading, high concentration of p-xylene and avoiding of high corrosive bromide.Fourthly, the oxidation of p-xylene catalyzed by metalloporphyrin and cobalt acetate is studied. Obviously better catalytic reactivity is acquired when metalloporphyrin and acetate cobalt used as co-catalyst than the two used separately. p-Xylene conversion and terephthalic acid yield are both increased. The effects of catalyst components and concentration, as well as reaction conditions on the co-catalysis of metalloporphyrin and acetate cobalt are investigated. p-Xylene conversion and terephthalic acid yield increased when temperature and air pressure elevated. The catalysts concentration should be kept in a proper context. The catalytic reactivity drops when part of acetate cobalt is substituted by equative amount of manganese acetate.Fifthly, the aerobic oxidation of p-toluic acid over metalloporphyrin and cobalt acetate is studied. Metalloporphyrins and cobalt acetate are both reactive catalyst in the p-toluic acid oxidation. And high p-toluic acid conversion and terephthalic acid yield is obtained when they are used together. The effects of catalysts and reaction conditions are also investigated.Sixthly, the substituent effect in the oxidation of substituent toluene catalyzed by metalloporphyrin and cobalt acetate is studied. And the results indicate that radical mechanism might be undergoing in the metalloporphyrin-cobalt acetate catalyzed oxidation of toluenes. The possible mechanism of the co-catalysis of metalloporphyrin-cobalt acetate in the oxidation of p-xylene is discussed. The peroxide produced by the catalysis of metalloporphyrin accelerates the chain initiation of cobalt acetate in the metalloporphyrin-cobalt acetate catalyzed reaction. Hence the whole reaction is accelerated and the p-xylene conversion is increased.In a summary, the catalysis of metalloporphyrin and cobalt acetate in the oxidation of p-xylene and p-toluic acid is studied, and the effects of catalysts and reaction conditions are investigated in this dissertation. A possible reaction mechanism of the co-catalysis is also proposed. This dissertation provides new materials in the field of theoretic and application aspects of biomimetic oxidation of hydrocarbons by metalloporphyrins, and is of importance to develop new oxidation route of p-xylene and other hydrocarbons.