Liquid phase hydrogenation of benzene to cyclohexene on ruthenium catalysts supported on zinc oxide-based binary oxides

A series of binary oxide-supported ruthenium catalysts with zinc oxide as a component of the support was prepared. Zinc oxide was a major component of the support, the other component was lanthanum oxide, zirconium oxide, chromium oxide, barium oxide, gallium oxide, strontium oxide, calcium oxide or magnesium oxide. Liquid phase hydrogenation of benzene to cyclohexene was studied on these catalysts in a stirred tank reactor at a hydrogen pressure of 2.5-6.0 MPa and 448 K. The reaction was operated in a kinetic-controlled regime. In order to have high selectivity to cyclohexene, a large amount of water should be present. In addition, the reaction medium should be an alkaline solution. The yield of cyclohexene was in the order: Ru/Ga₂O₃-ZnO > Ru/La₂O₃-ZnO > Ru/Cr₂O₃-ZnO > Ru/ZrO₂-ZnO > Ru/MgO-ZnO=Ru/CaO-ZnO=Ru/SrO-ZnO=Ru/BaO-ZnO.Ru/Ga₂O₃-ZnO demonstrated the highest selectivity and yield of cyclohexene. A model of the low solubilities of reactants in the water film surrounding the catalyst can explain the reaction behavior of the catalyst.