Glycerol conversion in the aqueous solution under hydrogen over Ru/C + an ion-exchange resin and its reaction mechanism

Of the various noble metals (Ru/C, Rh/C, Pt/C, and Pd/C) and acid catalysts [an ion-exchange resin (Amberlyst), H2SO4(aq), and HCl(aq)], the combination of Ru/C with Amberlyst is effective in the dehydration + hydrogenation (i.e., hydrogenolysis) of glycerol under mild reaction conditions (393 K, 8.0 MPa). The dehydration of glycerol to acetol is catalyzed by the acid catalysts. The subsequent hydrogenation of acetol on the metal catalysts gives 1,2-propanediol. The activity of the metal catalyst + Amberlyst in glycerol hydrogenolysis can be related to that of acetol hydrogenation over the metal catalysts. Regarding acid catalysts, H2SO4(aq) shows lower glycerol dehydration activity than Amberlyst, and HCl(aq) strongly decreases the activity of acetol hydrogenation on Ru/C. In addition, the OH group on Ru/C can also catalyze the dehydration of glycerol to 3-hydroxypropionaldehyde, which can then be converted to 1,3-propanediol through subsequent hydrogenation and other degradation products.