Study On Catalysts And Technology For The Oxidation Of Aromatic Hydrocarbons Using Hydrogen Peroxide As Green Oxidizer

Hydrogen peroxide is a kind of green oxidizer. The typical advantage of H₂O₂ is that it changes into water without poison residual after providing oxygen. Furthermore, liquid phase oxidation reactions when H₂O₂ is used as oxidizer often take place at low temperature. The reaction acts in mild atmosphere and the process is safe. Oxidation reaction using H2O2 will show greater advantage in the production of some organic oxides. Its application fields are wider and wider.H₂O₂ as oxidizer was used in the oxidation of benzene, toluene and p-chlorotoluene (PCT) in this paper, respectively. The catalytic performances in these reactions oxidized by H₂O₂ catalyzed by simple metallic compound such as mono-metallic, di-metallic and tri-metallic complex oxides were studied. Possible active components of the catalytic system can be analyzed by means of XRD and IR characterization and testing of some catalysts of good performance. The influences of different preparation conditions on activity of catalyst also were studied. The suitable process conditions for the hydroxylation of benzene catalyzed by Fe-Cu catalyst were reached.Mono-metal oxides had catalytic activity to the hydroxylation of benzene. Their activity order was: CuO> V₂O₅> Cr₂O₃≈α-Fe₂O₃> TiO₂. Among our di- metallic complex oxides, Fe-Cu had the highest activity to the hydroxylation of benzene. CuFe₂O₄ was the main crystal form in Fe-Cu catalyst tested by XRD method. There was α-Fe₂O₃ crystal form too. The same results were provided by IR analysis. In order to improve catalytic activity, the third metal element was added to the Fe-Cu di-metal oxides. Two kinds of catalysts including three metal ingredients had been prepared. Fe-Cu-V (II) was proved to be the best one. The activity had no obvious raise by comparing the conversion data of Fe-Cu-V (II ) and Fe-Cu. For the oxidation of toluene and p-chiorotoluene, the same results were obtained. Therefore,Fe-Cu was decided to be the most excellent one among all catalysts prepared because of better activity, easier way to produce it and its lower price.For the oxidation of toluene and PCT, catalytic activities were not high. The highest conversions of toluene and PCT were 5.29% and 5.8% obtained by the catalysis of Fe-Cu-V( II )which was considered to be the best in our catalysts. So the hydroxylation of benzene to phenol catalyzed by Fe-Cu oxides was main part in this thesis.Through the study of the effect of preparing conditions on the activity, the suitable condition was concluded that Fe/Cu (molar ratio) =7, uniformly adding ammonia water at the rate of 20mL/h, the amount of ammonia was 20% above the theoretical one, aging for 72 hours and calcinated at 550°C for 2 hours.On the basis of Fe-Cu catalyst, the process of the hydroxylation of benzene to phenol was optimized. The influence of solvents were studied first and mixed solvent of acetone and acetonitrile was decided to be suitable. The suitable conditions were gotten that the mass ratio of acetone to acetonitrile was 1 to 1, n (H2C>2)/n(benzene)=2/l (molar ratio), the amount of Fe-Cu catalyst was 10% ( according to the weight of benzene), reaction temperature was 60°C, H2O2 was added in 1 hour, the total reaction time was 4.5 hours. Under these conditions, the conversion of benzene was 20.34% and the selectivity of phenol was 96.22%.The above results had reference values in enlarging the application field of H2O2 in the preparation of organic oxides. At the same time, the use of Fe-Cu catalyst in the oxidation of benzene and its derivate with hydrogen peroxide was worth to being referred.