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

Abstract

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 H 2 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 C 2 -C 3 polyols.Catal. Sci. Technol. This journal is

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…If hydrogenolysis breaks selectively C-C bond, methanol will be the favourite reaction product; on the contrary, the breaking of the C-O bond will generate ethanol, that can be further converted into CO 2 or CH 4 ( Figure 6) [129]. Results similar to those obtained by Tsang and co-workers were obtained by other authors (Table 2).…”

“…The same performance obtained in presence of molecular hydrogen was observed with the gas phase mainly composed by H2 (81%-82%), followed by CO2 (about 18%). CO was never detected indicating the high performance of the Pd/Fe3O4 toward the water-gas-shift reaction [129].…”

“…If hydrogenolysis breaks selectively C-C bond, methanol will be the favourite reaction product; on the contrary, the breaking of the C-O bond will generate ethanol, that can be further converted into CO2 or CH4 ( Figure 6) [129]. Tsang and co-workers successfully used the co-precipitated Pd/Fe2O3 catalyst for methanol production from ethylene glycol [131].…”

“…Furthermore, the C-C bond breaking ability increases almost linearly with the concentration of Fe(0) present in the catalytic system. Mauriello et al studied the performance of the 5% Pd/Fe3O4 co-precipitated catalyst in the hydrogenolysis of EG [129]. At low temperature (180 °C), the Pd/Fe3O4 system shows nearly the same selectivity to methanol (49.9%) and ethanol (50.1%).…”

“…Specifically, results obtained in important "green and sustainable" reactions will be presented including: aqueous-phase reforming [128][129][130], hydrogenolysis [131][132][133][134][135][136] and CTH [137,138] of C6-C2 polyols, hydrogenolysis and transfer hydrogenolysis of furfural [139,140], hydrodeoxygenation of phenol derivatives [141,142], HDO and CTH of aromatic ethers [143][144][145]. All these reactions will be discussed in details with the aim to show the unicity of heterogeneous Pd-Fe catalysts that are suitable for a wide reductive valorization processes of all constituent components of lignocellulosic biomasses having the potential to be successfully used in modern biorefineries to produce simple bulk compounds.…”