Research Of Catalytic Oxidation Technology Of Cyclohexane

Oxidation reaction plays an important role in the organic synthesis industry. It is one of the main factors that cause the environmental pollution as well. This is an important area, as low selectivity of reaction, demands of rigorous experimental conditions and harm to mankind and the environment have made the replacement of traditional oxidants, such as Cr and Mn oxides and compounds, a paramount problem. Therefore, various green oxidants, such as oxygen, hydrogen peroxide etc, are applied to reach the friendly environment goal. In this paper, six catalysts were successfully prepared, and which were applied to catalyze selective oxidation of cyclohexane to cyclohexanone and cyclohexanol using oxygen. These catalysts were characterized by a series of methods, the effects of catalyst preparation conditions and oxidation reaction parameters on their catalytic performances were investigated in cyclohexane oxidation to cyclohexanone and cyclohexanol using oxygen as the oxidant. In this work, we have used the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol over hydrogen peroxide, to systematically investigate the catalytic performance of six kinds of catalysts.In this using30%hydrogen peroxide to oxidate cyclohexane to cyclohexanone experiment, ferrous sulfate is a preferable catalyst. Using10ml of acetone,0.20mL of cyclohexane,0.02g of ferrous sulfate,0.5mL of30%hydrogen peroxide at a reation temperature of80℃for10h, the conversion of cyclohexane was35.35%and the total selectivity to cyclohexanone and cyclohexanol was94.06%.In the reaction of oxidizing cyclohexane by30%hydrogen peroxide, the combination of using tungstic acid as catalyst and CDM-5as assistant catalyst was the best. The conversion of this oxidation is49.40%and the selectivity to cyclohexanone and cyclohexanol was96.08%when we use lOmL of acetone,0.2mL of cyclohexane,0.02g of tungstic acid,0.01g of CDM-5,1.0mL of30%hydrogen peroxide at a reation temperature of70℃for9h.The catalyst supported on HZSM-5molecular sieves (Cu/HZSM-5) was prepared by ion exchange and characterized by XRD, BET, ICP, FT-IR and TG/DTA. It is proposed that CuO crystallization occurs between300and400℃, and there exist various ligand bonds interactions between the copper species and the molecular sieve matrix. Cu/HZSM-5exhibits the best performance when the Cu(copper nitrate) loading is10%, the ion exchange temperature reaches80℃, reaction time reaches8h and the calcination temperature reaches600℃. Using0.5mL of cyclohexane,10mL of acetonitrile,4ml of hydrogen peroxide and0.03g of catalyst at a reaction temperature of65℃for6h, the cyclohexane conversion was43.1%and the total selectivity to cyclohexanol and cyclohexanone was95.7%.The new type of Co-Mo/V2O5catalyst was prepared by impregnation method and characterized by XRD, BET and FT-IR. It is observed that the incomplete crystalline phase CoMoO4(2θ=28.51°) and CoMoO3(2θ=18.06°) have catalytic activity, demonstrating that there is interaction between pure V2O5and doped components. The Co-Mo/V2O5catalyst exhibits the best performance when the Mo loading is20%and Co loading is5%, the immersion time reaches1h and the calcination reaches600℃. Using0.5mL of cyclohexane,3mL of hydrogen peroxide and30mg of catalyst at a reaction temperature of55℃for3h, the cyclohexane conversion was39.1%and the total selectivity to cyclohexanol and cyclohexanone was100%.The CuPMo/V2O5catalyst was prepared by impregnation method and characterized by XRD, BET and FT-IR. It is observed that PMo and CuO were well dispersed on the surface of V2O5, thus indicating that the doping components had no obvious effect on the original structure of V2O5. The CuPMo/V2O5catalyst exhibits the best performance when it is impregnated at room temperature for12h and calcinated at320℃. Using0.5mL of cyclohexane,3mL of hydrogen peroxide and30mg of catalyst at a reaction temperature of65℃for3h, the cyclohexane conversion was53.6%and the total selectivity to cyclohexanol and cyclohexanone was100%.In this work, the VPO catalyst and the Bi-promoted VPO catalyst were prepared, and these catalysts were investigated by means of XRD, FT-IR, the determination of average valence state of vanadium and electronic speculum. It is indicated the addition of Bi has a positive effect on the catalyst, which will adjust the ratio of V4+/V5properly, thus increasing the content of oxides. The VPO catalyst exhibits the best performance under the condition of Bi/V=0.1, P/V=0.9at reduction temperature of120℃and calcination temperature of400℃for12h. The main property of the catalyst precursor is (VO)2H4P2O7, and it was converted to VOPO4, playing as the active phase.By preparing the Bi-VPO catakyst in advance, the aim of this work is to investigate the effect of solvent and its dosage, the catalyst and hydrogen peroxide dosage, reaction temperature and reaction time on reaction. In the end, with the optimized condition of using0.6mL of cyclohexane,0.015g of Bi-VPO, lOmL of acetone,3.0mL of30%hydrogen peroxide, at a temperature of65℃for8h, the cyclohexane conversion was81.4%, the cyclohexanone yield was58.2%and the cyclohexanol yield was23.2%.