Sorbitol transformation over bimetallic Ru-Pt/SiO2-Al2O3 catalysts: Effect of the preparation method

摘要

Sorbitol hydrogenolysis in aqueous medium was carried out over Ru-Pt based catalysts supported on SiO2-Al2O3 and synthetized by three preparation methods (co-impregnation, successive impregnations or a surface redox deposition). These catalysts were characterized by N-2 isothermal adsorption desorption, transmission electron microscopy, H-2 chemisorption, temperature programmed reduction and by the model reaction in gas phase of cyclohexane dehydrogenation. The catalytic performances were compared to those of monometallic catalysts (Pt/SiO2-Al2O3 and Ru/SiO2-Al2O3) under hydrothermal conditions, in a batch reactor at 240 degrees C under 60 bar H-2 pressure. The main products were poly- and mono-oxygenated compounds in liquid phase and hydrocarbons in gaseous phase. The best yield of hydrocarbons was obtained in the presence of Ru-Pt bimetallic catalyst prepared by successive impregnations, for which a synergetic effect was observed. This effect can be explained by the existence of bimetallic particles of small size favoring an electronic exchange from Ru to Pt. Under the experimental conditions used in this study, it appeared that the reaction pathway of sorbitol transformation was not the same on Pt- or Ru-based catalysts. (C) 2016 Elsevier Ltd. All rights reserved.