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 onesugarwas 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 aresult the carbon identification was complete formost of the substrates. The C5 compounds(xylitol and xylose)did not havea complete carbon balance as a consequenceof complex furans chemistry. The polyols displayed an elevated production of hydrogen and carbon dioxide at allconditions, but it couldbe evenimproved bytemperature increase and addition of formic acid. The sugar (xylose) shows changes in the hydrogen selectivity with the conditionsincreasing the alkane production withtemperature and formic acid addition. Accordingto the resultstheretro-aldol reaction it is the main route forC-C bond cleavage,which ispromoted by dehydrogenation or dehydration reactions. The presence of decarbonylation was observed but tolower extentand it could have beenrelated to alkane production. Experimentswith different catalyst composition were done. Large changes in the gas products formationwere observed. The best ratio for Pt and Pd was 2:1 respectively, because it gavean increase in selectivity to hydrogen and stoppedthe carbon monoxide production in most of the conditionstested. The ethylene glycol APR reaction path was condensed tothe most abundantproducts for the model generation. The final kinetic model displayeda 99.56% of correspondencewith the experimental data. The reactor behaviorwas described using a plug flow model.