Study Of Catalytic Oxidation Of Cyclohexane Over Supported Metalloporphyrin In Fixed-bed Reactor

Enzyme is a bio-catalyst, which has perfect catalytic activity and selectivity. Therefore, with environment pollutting and global warmming up, researching and developing a biomimetic catalyst with high catalytic activity and selectivity is significant and valuable. Metalloporphyrin is a biomimetic catalyst,which has being extensively studied and applied in alkane oxidation and alkene epoxidation. However, metalloporphyrin has some shortcoming in homogeneous system, such as self-oxidation, dimerization, and unstability. Furthermore, the process of autoclave-type reaction is often complex and not easy to control. Thus, homogeneous catalysts are supported and applied in the fixed bed reactor, which may overcoming the shortcomming mentioned above and keep running without stopping when reaction is started.In this thesis, the influence of carriers and preparation methods on the performance of metalloporphyrins catalysts are discussed. We have also investigated the influence of different types of catalysts on the gas-phase oxidation reaction of cyclohexane, and then we selected the best catalyst with the highest catalytic performance and refined the reaction conditions. In the end, we discussed the reaction mechanism. The main contents are as follows:1. The off-line and online analytical methods were investigated, and the method of real-time online analysis was established. In this method, chlorobenzene was used as the internal standard.2. Catalysts such as supported metalloporphyrin, oxides, and modification 13X molecular sieve were prepared and the catalytic performance of these catalyts for the oxidation reaction of cyclohexane were measured. Then TPPCo/13X catalyst was found to possess the highest catalytic performance. The sequence of the catalytic activity is as following:supported metalloporphyrin>modified 13X molecular sieves>oxides.3. The stability of catalyst was investigated, and the conversion of cyclohexane was decreased from 18.2% to 16.1% after 20 h. The selectivity of cyclohexene, Cyclohexanol and cyclohexanone had little difference. The selectivity of cyclohexanol and cyclohexanone was kept at about 3-4%, by contrast, the selectivity of cyclohexene was decreased by 5%, and the selectivity of pentanal was decreased at first and then increased, from the 1.4% to 0.6%.4. The stability of catalyst was investigated. When reaction temperature was elevated to 280℃for 3 hours, the catalyst still had high activity. when repeated three times, the conversion of cyclohexane, and the selectivity of cyclohexene, cyclohexanol and cyclohexanone was changed little,compared with the fresh.5. Finally, the reaction processes and the paths of main productions were investigated and analyzed according to the experimental data and phenomena.