Glycerol hydrogenolysis to propane diols was carried out over Ru/C catalysts using different solid acids as co-catalysts. Solid acids such as niobia, 12-tungstophosphoric acid (TPA) supported on zirconia, cesium salt of TPA and cesium salt of TPA supported on zirconia were used. The acidities of the solid acid catalysts were measured by temperature programmed desorption of ammonia. The conversion of glycerol depends an the total acidity of the catalysts and there exists a linear correlation between conversion and acidity. The selectivity towards 1,2-propanediol and the glycerol conversion varied with the change in the concentrations of both Ru/C and solid acid catalysts, suggesting a synergetic effect of the reaction. This reaction requires minimum amount of both acid and metal sites to obtain reasonable activity. Different reaction parameters were studied and optimized reaction conditions were established. (C) 2008 Published by Elsevier B.V.