Investigation On Selective Aerobic Oxidation Of P-Xylene Catalyzed By Metalloporphyrins

p-Xylene, one of easily available raw petroleum materials, was mainly oxidized to terephthalic acid and p-toluic acid in industry. Environmental and economic presses, in the field of p-xylene oxidation, are forcing industry to develop new catalytic routes to produce more higher additional value products, p-tolualdehyde and p-toluoalcohol, exclusively employing cheap, clean and atom efficient oxidants such as O2. Recently, extensive attention has been paid to metalloporhyrins, analogous complexes mimicing the behavior of cytochrome P-450 that can use dioxygen to functionalize hydrocarbons under ambient condtions.The selective aerobic oxidation of p-xylene catalyzed by metalloporphyrins without consumption of co-reductant and solvent is firstly investigated in attempting to develop a new process for production of p-tolualdehyde and p-toluoalcohol with high additional value. The preliminary investigation focuses on a new green catalytic system, the first generation metalloporphyrins -air-p-xylene system, which is potentially to be applied in chemical industry hereafter. The process of this reaction is showed as follows:The contents of this thesis are presented as follows:1. Seven kinds of the first generation poprhyrins were synthesized and characterized including five monometalloporphyrins, one -oxo-bisironoporphyrin and tetraphenylporphyrin. All of them are relatively inexpensive and readily prepared in comparison with the second and the thirdgeneration metalloporphyrins.2. In view of industrialization feasibility, a brief process flow diagram in a semi-batch manner was designed for this oxidation reaction. Moreover, a common autoclave was modified to facilitate our system.3. The effects of various process parameters, such as period of reaction, temperature, pressure, and catalyst loading on the conversion of p-xylene as well as yield of p-tolualdehyde and p-toluoalcohol were explored by means of numerous primary experiments using MnTPPOAc as catalyst. It is observed that elevation of temperature and prolongation of reaction time can enhance the conversion of p-xylene while the yield of p-tolualdehyde and p-toluoalcohol descends simultaneously. With oxygen pressure increasing, the yield of p-tolualdehyde and p-toluoalcohol decreases. The conversion of p-xylene, however, ascends initially and then declines. Catalyst loading increase is not always of advantage to catalytic activities of metalloporphyrins. Increasing the catalyst loading to 3.44XlCHmol/l inhibits the activities of metalloporphyrins.4. Comparison of the activities of the catalysts FeTPPCI, MnTPPCI, CuTPP, and CoTPP indicates that the last one is more active than the others, and is screened out as the best catalyst in our system. Meanwhile there is no correlation between catalytic activities and the reduction potentials of metalloporphyrins in our system as compared with that of the second and third generation metalloporphyrins. It is noteworthy that CuTPP catalyst, contrary to previous reports in monoxygenase-catalyzed system, has relative high activities in our system. Furthermore, the -oxodimer (FeTPP) 2O is shown to have significantly better activity than corresponding monomer FeTPPCI.5. The multicollinearities, derived from uniform design for forecasting the optimized process parameters of oxidation of p-xylene in the presence of CoTPP catalyst, are successfully resolved by ridge regression. Under optimum condition (temperature=160, pressure= 1.3 MP, period of reaction=180 min, air flow rate = 40 L/h, catalyst loading=11mg.), it is possible to obtain 12.70 % conversion of p-xylene in calculation, 11.62% conversion in experiment. In addition, at the reaction conditions of temperature 120, pressure 0.4 MP, reaction time 60 min, air flow rate 40 L/h in the presence of 11 mg CoTPP catalyst, the yield ofp-tolualdehyde and p-toluoalcohol is 86.49% in calculation, 85.09% in experiment. 6. Finally, according to our experim...