Study On The Oxidation Of Cyclohexane To Ka Oil Over Heterogeneous Catalysts By Molecular Oxygen

The aerial oxidation of cyclohexane to cyclohexanol and cyclohexanone(KA oil) is an important representative for the hydrocarbon oxidation, andthe research on this reaction is of significant scientific and industrialimportance. Current commercial production of KA oil from cyclohexaneaerial oxidation involves either non-catalysis or homogeneous catalyst,being still associated with many drawbacks, such as, low conversion ofcyclohexane and selectivity to KA oil, high temperature and pressure, anddifficult in separate operation, and so on. They are thereforenon-environmental friendly processes. In the present work, a series of novelheterogeneous catalysts were developed and utilized in the aerial oxidationof cyclohexane to KA oil. The results exhibit a promising industrializationforeground of cyclohexane aerial oxidation to KA oil over heterogeneouscatalysts. The main points are as follows:1) In present work, ZSM-5 has been modified by adding Cu, Co, Fenitrates to the synthesis process respectively, and then have beencharacterised by XRD, AAS. In order to arrive the best synthesis conditions,the oxidation of cyclohexane over the modified catalysts, used molecularoxygen in different conditions, were investigated. Among thosemetal-exchanged ZSM-5 catalysts tested, Co(a2)-ZSM-5 catalysts showedthe best activity for the oxidation of cyclohexane, and the best conversionof cyclohexane reached 13.0% with the selectivity of KA oil being 80.4% atreaction time of 12 h.2) Oxidation of cyclohexane with molecular oxygen to KA oil wassystematically studied over these Co doped anatase TiO2 catalysts,synthesized by sol-gel method. These catalysts material were characterizedby XRD, Raman, XPS, UV-vis etc. The results indicated that Co wasincorporated in the TiO2 lattice as Co2+ and substituted for the Ti site withno evidence of metallic Co. Also, it showed oxygen vacancies played amajor role in producing peroxospecies O22 -. The absence of peroxospeciesO22 - is beneficial for cyclohexne oxidation to KA oil.3) Considering of recycling catalyst Co/TiO2-450 and specialty of cyclohexane oxidation, we designed a new gas-solid-liquid reactor for this synthesis process. It not only solved the problems, involved the losing of catalyst active and lack of react time, but also increased the conversion of cyclohexane and selectivity of KA oil. Then the effects of cyclohexane oxidation to KA oil, such as conditions of the synthesis of catalysts, O2 pressure, reaction temperature, reaction time, the mount of acidic acid and different initiators etc, were investigated over Co/TiO2-450. The results indicated that the conditions of preparation catalyst, the mol ratio of Co/Ti is 0.04:1, crystallization time was 6 hours, had the optimum function. Under the suitable react conditions, the conversion of cyclohexane could reach 14.1% , with 95.9% of KA oil selectivity.4) The mechanism of areal oxidation of cyclohexane to KA oil was been studied in the new model over the heterogeneous Co-TiO2 catalyst. The study for the annihilated free radical CCl4 and captured CH3I free radicals indicated that the oxidation of cyclohexane to KA oil involved the key step of the cyclohexane radicals formation.