Selective Of Hydrogenation Of Benzene To Cyclohexene

Cyclohexene is a very important organic chemical materials which is widely used in producing pesticides, medicine, feed addition, polyester and so on. The largest value of cyclohexene is that it can be hydrated to cyclohexanol, which can be used to produce cyclohexanone and adipic acid. Therefore, many researchers focus on the study of the catalyst for selective hydrogenation of benzene to cyclohexene. In 1989,Asahi Chemical Industry Corporation commercialize this technique firstly. In 1995, our country this advanced production route was introduced into our country. But the core of this technique, preparation of catalysts is still keep secret. Therefore, It is of great significance to study on benzene partial hydrogenation to cyclohexene.Firstly, supported Ru catalysts were prepared by precipitation method,and the influence of different carrier on catalytic properties was investigated. On the basis of this investigation,we also studied the influence of different promoter selective hydrogenation of benzene to cyclohexene. The results show that the catalyst used ZrO₂ as carrier, Fe as promoter and with Fe/Ru of 16% give the best catalytic performance. The conversion of benzene was 49.68% , selectivity to cyclohexene was 39 .97%.Unsupported Ru catalysts were prepared by precipitation method and the influence of Zn or La as promoter on catalytic properties was investigated. The results indicated La content of 8% gives better performance.The influences of different factors on selective hydrogenation of benzene to cyclohexene were studied, including inorganic additives ZnSO₄ï¹'7H₂O, disperser ZrO₂, amount of catalysts, the ratio of benzene to water,the reaction temperature and pressure. The results indicate that optima reaction operating condition as the following (the quantity of benzene was 10 ml): ZnSO₄ï¹'7H₂O 4.0g, added quantity of ZrO₂ 1.0g, catalyst 0.2g, ratio of benzene to water was 3;reaction temperature 150℃;reaction pressure 5.0MPa.Amorphous Ru-Fe-B/ZrO₂ catalysts were prepared by chemical reduction method. The influences of concentration of reducing agent NaBH4 and pretreatment time on catalytic properties were investigated. The results indicate that the optima condition is as the following : concentration of reducing agent NaBH4 2.50 mol/l,pretreatment time 18 hours.The prepared catalysts were characterized by XRD, N2 adorption-desorption, and laser particle size analyzer. The relationship between the active component, BET surface area, pore structure and its catalytic performance was discussed.