The Preparation Of Nano-Metal Catalyst And Its Effect On The Cyclohexane Oxidation Reaction

The conversion of cyclohexane to cyclohexanone[K] and cyclohexanol[A] with high selectivity is of importance as these compounds are utilized in the manufacture of nylon-6 and nylon-66. Meanwhile, KA are also important industrial chemicals and important intermediates for fine chemical industry, such as the synthetic additives of food, medicine, coating materials, dyestuff, and so on. Currently, cobalt is used as the main catalyst system in both homogeneous and heterogeneous catalysis, and the conversions of cyclohexane have to be kept well below 10% to achieve reasonable selectivities and to avoid over-oxidation. The oxidation of cyclohexane is still one of the major challenges of modern catalysis. In this work, studies on key factors to improve the efficiency of oxidation of cyclohexane to KA oil and development efficient catalyst for the process using molecular oxygen as oxidant in liquid-phase, were carried out.Nanostructered iron oxide is development. This catalyst shows good activity and selectivity for cyclohexane oxidation in mild conditions using air as oxidant. The effect of solution of iron pentacarbonyl and ultrasonic power on oxidation reaction is discussed. The suitable condition of preparing catalyst, namely the solution of iron pentacarbonyl is 0.5mol/L, the ultrasonic power is 100W, is obtained. Meanwhile, the effects of reaction time, reaction temperature, concentration of catalyst, initiator amount and air amount on the oxidation reaction of cyclohexane are studied in the reaction system. The optimum oxidation reaction conditions are obtained using isobutylaldehyde as initiator and air as oxidant as follows: reaction pressure is 1.0 atm, temperature 70℃and reaction time 3 h. Under these conditions, the conversion of cyclohexane oxidation was 23.8 %, the selectivity of cyclohexanol,clohexanone and cyclohexyl hydroperoxide was 94. 5 %.Finally, the new supported catalyst of CoO/CNTs is prepared using the method of impregnation-deposition. The effect of solution of cobalt nitrate, reaction time, temperature, concentration of catalyst, initiator amount and pressure on the oxidation reaction of cyclohexane oxidation are investigated. The optimum oxidation reaction conditions are also obtained using tert-butyl hydroperoxide as initiator and air as oxidant as follows: the solution of cobalt nitrate is 0.5mol/L, pressure 1.0MPa, temperature 150℃and reaction time 2h. Under the condition, the conversion of cyclohexane oxidation was 14.2%, the selectivity of cyclohexanol,clohexanone and cyclohexyl hydroperoxide was 90.2 %.