Partial hydrogenation of benzene on Ru-Zn/SiO2 catalysts

A series of silica-supported ruthenium-zine catalysts with various contents of zinc were prepared. These catalysts were characterized with temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H-2-TPD), and X-ray diffraction (XRD). The reaction of partial hydrogenation of benzene was carried out in a batch reactor at a pressure of 3.36 MPa. The reduction of Ru-Zn/SiO2 catalysts occurs at a much higher temperature, as compared to the Ru/SiO2 catalyst. The results suggested that ruthenium and zinc were in close proximity with each other. The reduction process of ruthenium oxide was retarded because of Ru-Zn interaction. The profiles of H-2-TPD for Ru-Zn/SiO2 catalysts show two desorption peaks. The total amount of desorbed hydrogen decreased with an increase in the zinc concentration. The catalytic activity also decreased with an increase of the zinc concentration in the catalyst. The area of the low-temperature H-2-TPD peak, in contrast, increased with an increase of the zinc concentration. In addition, the selectivity to cyclohexene can be correlated with the area of this low-temperature desorption peak.