Influence of catalyst pretreatment on catalytic properties and performances of Ru–Re/SiO2 in glycerol hydrogenolysis to propanediols

Abstract: Bimetallic Ru–Re/SiO2 and monometallic Ru/SiO2 catalysts were prepared by impregnation method and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160°C, 8.0MPa and 8h. Ru–Re/SiO2 showed much higher activity in the hydrogenolysis of glycerol than Ru/SiO2, and the pretreatment conditions of the catalyst precursors had great influence on the catalytic performance of both Ru–Re/SiO2 and Ru/SiO2 catalysts. The physicochemical properties of Ru–Re/SiO2 and Ru/SiO2, such as specific surface areas, crystal phases, morphologies/microstructures, surface element states, reduction behaviors and dispersion of Ru metal, were characterized by N2 adsorption/desorption, XRD, Raman, TEM–EDX, XPS, H2-TPR and CO chemisorption. The results of XRD, TEM–EDX and CO chemisorption characterizations showed that Re component had an effect on promoting the dispersion of Ru species on the surface of SiO2, and the measurements of H2-TPR revealed that the co-existence of Re and Ru components on SiO2 changed the respective reduction behavior of Re or Ru alone. High pre-reduction temperatures would decrease the activities of Ru–Re/SiO2 and Ru/SiO2 catalysts, compared with the corresponding calcined catalysts (without pre-reduction), which actually went through an in-situ reduction during the reaction. XPS analysis indicated that Ru species was in Ru0 metal state, while Re species was mostly in Re oxide state in the spent Ru–Re/SiO2 sample. Re component was probably in rhenium oxide state rather than Re0 metal state to take part in the reaction via interaction with Ru0 metal. [Copyright &y& Elsevier]