Selective Hydrogenation Of Benzene To Cyclohexene Over Ru Catalysts

Cyclohexene is an important raw material. As intermediate, cyclohexene can be used in medicine, pesticide, dye, washes, dynamite, feedstuff, polyester, and other fine chemicals.Selective hydrogenation of benzene to cyclohexene over Ru is the best method to obtain cyclohexene. In this paper, we analyzed the important roles of mass transfer in selective hydrogenation of benzene. It was concluded that Cyclohexene is obtained due to the existence of a water films. The water films around catalyst was formed, and the water films could accelerate the desorption of cyclohexene from ruthenium sites due to much low solubility of cyclohexene in water. However, the activity is also rather low because of the existence of the water films around catalyst.In order to increase the selectivity and activity of ruthenium catalyst, Enhancing the hydrophilicity and decreasing the particle size of ruthenium is done, and three kinds of catalysts were prepared: (1) Borate acid was impregnated in ZrO2-ZnO to form zinc borate. (2) Nano ruthenium supported on zirconium dioxide was prepared by reducing the mixture of ruthenium trichloride and nano zirconium dioxide by potassium borohydride. (3) Ruthenium colloid supported on silica was prepared by microemulsions. More than 75% selectivity of cyclohexene on conversion 40% was achieved by the second catalyst. The TON(H₂) was 0.3 S-1. With the third catalyst, over 76% selectivity of cyclohexene on conversion 40% was achieved, and the max yield of cyclohexene was more than 42% with an TON(H₂) of 0.76 S-1.