Selective Hydrogenation Of Benzene To Cyclohexene

Cyclohexene is an importaint organic synthetic intermediate and raw chemicalmaterial，which has broad applications in medicine, pesticide, dye, washes, dynamite,feedstuff, polyester, and other fine chemicals.Till now, selective hydrogenation of benzene to cyclohexene is the best method toobtain cyclohexene. In this paper, through the summary of literatures we point out that themass transfer is one of the key factors in selective hydrogenation of benzene. And thedifference of solubility between benzene and cyclohexene in water is the key to achieveselective hydrogenation of benzene to cyclohexene. The adsorption of water on the surfaceof solid catalyst formed a water layer, which can accelerate the adsorption of cyclohexenefrom the active catalytic sites due to much lower solubility of cyclohexene in water. So thekey to promote the selectivity of cyclohexene is to improve the hydrophilicity of thecatalyst. Therefore, the crystal formation, the particle diameter and the porous structures ofthe catalyst et al, are the important factors that can influence the result of selectivehydrogenation of benzene to cyclohexene.The aim of this paper is to prepare a ruthenium catalyst with high selectivity andactivity, and to explore the different preparation methods and conditions on the influence ofthe catalyst. Impregnation method, precipitation method and chemical reduction method allwere used to prepare ruthenium catalyst. We explored the influences of the low alcoholsorganic additive, the pretreatment, KBH₄reduction conditions and the supports on theperformance of the catalyst and tried to determine the best preparation and reactionconditions of the catalyst. Zirconia supported nano ruthenium catalyst was prepared byreducing ruthenium chloride, and gave a conversion of66%and a selectivity ofcyclohexene over65%. We found that the monoclinic zirconia can significantly enhancethe the selectivity of the catalyst, which could be obtained using ZrO（NO₃）₂·2H₂O as rawmaterial, hydrothermal synthesis for18h, and washing with water for several times, andthen washing with a few ethanol.