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Studies Of Substituent Effects In Cyclohexane Oxidation With Air Catalyzed And Induced By Metalloporphyrins

Posted on:2003-03-31Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiuFull Text:PDF
GTID:2121360092970205Subject:Organic Chemistry
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Although there have been major advances in the oxidation of saturated hydrocarbons with molecular oxygen,the development of effective and selective methods for the catalytic functionalization of hydrocarbons still remains a major challenge in oxidation chemistry. In particular,selective oxidation of alkanes with dioxygen to oxygen-containing compounds such as alcohols and ketones is a very important industrial process. Traditional alkane oxidation with dioxygen often suffers from relatively harsh conditions and limited conversion and selectivity. For instance,oxidation of cyclohexane to a mixture of cyclohexanone and cyclohexanol (K/A oil) is now carried out using a soluble cobalt catalyst in industrial scale worldwide. The drawback of this process is that the oxidation must be operated in 3-6% conversion of cyclohexnane to maintain higher selectivity (75-80%) to the K/A oil. Although much effort has been made to develop an effective oxidation system of cyclohexane with molecular oxygen,this process is currently employed without major modification.Recently we have developed a novel method for cyclohexane oxidation with dioxygen using the metalloporphyrin as a catalyst under mild condition in absence of any cocatalyst or coreductant. Thus,cyclohexane can be converted into K/A oil in higher conversion (12.55%) and turnover of catalysts reach 90000 under 0.8 MPa atmosphere pressure at 145C. This method would provide an interesting approach to cyclohexane oxidation with air in industrial scale.The contents of this thesis are presented as follows:1. In the introduction,we presented the application of the metalloporphyrins and generalized the development of metalloporphyrins in catalyzing alkanes oxidation with dioxygen. The current industrial technics of cyclohexane oxidation into cyclohexanone were introduced. Furtheremore,the theory of the substitent effects and linear free energy relationship was also presented in detail.2. The synthesis and characterization of nine kinds of porphines andtwenty-four kinds of metalloporphyrins bearing different substituents werepresented in the second chapter. The investigation of the UV-Vis of porphinesshowed that an electron-donating substituent plays a positive role of the molar absorbance coefficient e.3. In the third chapter we introduced the studies of the catalytic oxidation. The design and setting of the reaction equipments and the analysis methods to theproducts were presented at first. The catalysis of (TPPFem)2O for the oxidation of cyclohexane into cyclohexanone and cylcohexanol with air was studied for the first time. The reaction gained conversion of alkane 12.55% and turnover of catalyst 90000(based on the metal),which were above 1.5 times higher than that of monometallopophyrins. The effects of various parameters,such as reaction time,temperature,pressure and concentration of catalyst and so on,were explored by means of serious experiments and the optimum conditions were obtained.4. From the fourth to the sixth chapter we introduced the results of the cyclohexane oxidations with air catalyzed respectively by monoironporphyrins,monomanganeseporphyrins and bisironporphyrins bearing different substituents. The Hammett equations of the three series of catalysts showed the comparison of the catalytic activity.5. In the end of this thesis we discussed the hypothetic mechanism of the cyclohexane oxidation catalyzed by metalloporphyrins according the results of comparative experiments and some literature reports.
Keywords/Search Tags:Metalloporphyrin, Cyclohexane, Catalytic oxidation, Air, Substituent effects
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