Hydrogenolysis vs. aqueous phase reforming (APR) of glycerol promoted by a heterogeneous Pd/Fe catalyst

The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated under mild reaction conditions, using water as the reaction medium and Pd/Fe as the catalyst. The experiments, in the presence of added H2 or under inert atmosphere, clearly show that the dehydration/hydrogenation route is the key step in the case of C–O bond cleavage (hydrogenolysis) while dehydrogenation is a prerequisite for C–C bond breaking (APR), with the latter favoured at higher reaction temperatures. The temperature dependence of the C–C and C–O bond rupture is discussed by taking into account the bond energies involved in the competitive hydrogenolysis and APR reactions. Finally, the Pd/Fe catalyst was also tested in the hydrogenolysis and APR of ethylene glycol in the same temperature range, with the aim of clarifying the selective cleavage of C–O and C–C bonds in biomass derived C2–C3 polyols.