STUDY ON THE NOVEL Ru CSTALYSTS FOR SELECTIVE HYDROGENATION OF BENZENE TO CYCLOHEXENE

Cyclohexene can be hydrated to cyclohexanol and be oxidized to cyclohexanone and adipic acid. It is of great synthetic and industrial interest for partial hydrogenation of benzene to cyclohexene, by which the procedure of e -caprolactam and adipic acid is shortened. In recent years, many chemical industry corporation in developed countries have been attaching importance to the study of partial hydrogenation of benzene to cyclohexene. In 1989, Asahi Chemical Industry Corporation in Japan built Nylon-66 product line, in which the critical path is partial hydrogenation of benzene to cyclohexene. The product line was introduced to China in 1995. It is of great significance to study on the catalyst of partial hydrogenation of benzene to cyclohexene and to exploit the novel catalyst of ourselves. This paper stresses on the study of the so 1-gel deposit-precipatant method and chemical reduction method. The sol-gel deposit-precipatant method has been systematically studied. By chemical reduction method catalysts with high activity and high selectivity have been prepared. Kinetics of partial hydrogenation of benzene to cyclohexene over ruthenium catalyst has also been discussed. The sol-gel deposit-precipatant is a new method for precursor loading. Based on it's fundamental, silicon sol was prepared from sodium silicate and/or soluble glass by ion-exchange. The precursor was dropped into the sol to agglomerate and deposit together, followed by aging, filtering, washing, drying and activating, to get catalyst with high dispersity. The catalysts were evaluated in an autoclave at 140 5.OMpa and 900 rpm. The effects of pH value, Si02 concentration, carrier, solvent, assistants and additives on the catalysts were systematically investigated. It was found that Si02 is a good carrier for the catalysts. Preparation conditions of the catalysts were optimized as following:At 60 ,glycol solution of RuCI3 and CuCI2 is dropped into 2% silicon sol of which pH value is about 5-7 for 30 mm; the system is aged at room temperature for 8-I Oh; dried at 80 ; milled; and reduced at 400C with 6L/h H2 for 8h. The obtained catalyst was used for hydrogenation of benzene in the presence of propanediol for 30mm to give cyclohexene selectivity 31% at benzene conversion 60%. XRD shows that active component is highly dispersed. The method has application prospect for catalyst preparation. Chemical reduction method is also called chemical deposition method. It makes use of the molecules, ions and atoms in the solution as raw material to prepare non-crystal. The procedure is easy to operate. Small particles with large surfaces can be obtained, which enables catalysts have high activity and high selectivity. Ru-M-B/Zr02 catalysts, in which M is transitional metal elements, have made great progress. Catalysts were evaluated by Nylon-66 Saltworks in Pingdingshan(Henan Province,China ) under the same conditions compared with import catalysts. It has been found that Y 40 (activity of at benzene conversion 40% per gram catalyst in an hour) and S40 (selectivity to cyclohexene at benzene conversion 40%) were 271.5 and 83.3% at 33mm respectively, which were superior to that of import catalysts and what the patent JP 243039/63 reported. In the patent cyclohexene selectivity 76% at benzene conversion 39% was obtained with RuIZrO2 catalyst at 150 慍 5 .OMpa for 1 20mm. The effects of components, preparation and reaction conditions on...