Reforming of Glycerol Over Pt/C and Pt-Re/C in Aqueous Phase: Understanding Catalyst Function and Reaction Pathways for Hydrogen Production

Study of bioliquid reforming in aqueous phase is of increasing interest due to its potential application in fuel cells powered by renewable sources. Pt and Re-promoted Pt are considered promising catalysts for the catalytic process occurring at the liquid-solid interface. Despite the encouraging progress in demonstrating high hydrogen selectivity achieved on Pt or high conversion obtained on Pt-Re, fundamental understanding of the catalyst function under working conditions and its effect on reaction pathways is not complete. For this reason, we have studied structures of the catalysts by in-situ characterization techniques and identified a dual-functionality of Pt-Re under hydrothermal conditions: modification of Pt electronic structure through charge transfer and formation of ReOx. Our kinetic study suggests that the main reaction pathways occurring over Pt/C is through dehydrogenation of polyols followed by cleaving C-C bond of aldehyde intermediates. Addition of Re increases conversion of glycerol, but the ReOx formed in APR process also provide acidity to facilitate C-O scission through dehydration pathway competing with C-C breaking pathway. Because C-O scission followed by hydrogenation consumes hydrogen generated by C-C cleavage, the hydrogen selectivity decreases with addition of Re. However, with the conversion enhancement by Re addition, hydrogen TOF could be maximized by controlling Pt/Re ratio. In addition, effect of addition of base and reaction conditions on the reaction pathways will be discussed in order to optimize hydrogen production.