Aqueous phase reforming of renewables for hydrogen production in presence of supported platinum and palladium catalysts

The aqueous phase reforming (APR) of five polyols and one sugar was studied over Pt/Pd catalysts supported on mesoporous carbon. The temperatures were between 175°C to 225°C and addition of formic acid was studied for potential industrial application. During the analyses 45 compounds were identified and quantified (17 in the gas phase and 28 in the liquid phase). As a result the carbon identification was complete for most of the substrates. The C5 compounds (xylitol and xylose) did not have a complete carbon balance as a consequence of complex furans chemistry. The polyols displayed an elevated production of hydrogen and carbon dioxide at all conditions, but it could be even improved by temperature increase and addition of formic acid. The sugar (xylose) shows changes in the hydrogen selectivity with the conditions increasing the alkane production with temperature and formic acid addition. According to the results the retro-aldol reaction it is the main route for C-C bond cleavage, which is promoted by dehydrogenation or dehydration reactions. The presence of decarbonylation was observed but to lower extent and it could have been related to alkane production. Experiments with different catalyst composition were done. Large changes in the gas products formation were observed. The best ratio for Pt and Pd was 2:1 respectively, because it gave an increase in selectivity to hydrogen and stopped the carbon monoxide production in most of the conditions tested. The ethylene glycol APR reaction path was condensed to the most abundant products for the model generation. The final kinetic model displayed a 99.56% of correspondence with the experimental data. The reactor behavior was described using a plug flow model.