Hydrogen production from glucose using Ru/Al2O3 catalyst in supercritical water

Glucose, as a model biomass compound, was catalytically reformed in supercritical water to produce hydrogen. The reforming experiments were conducted in a continuous tubular reactor with and without Ru/Al2O3 catalyst at short residence times. The addition of catalyst significantly enhanced the overall conversion and hydrogen yield, and reduced methane formation. The gaseous products contained mainly hydrogen, carbon dioxide, methane, and a small amount of carbon monoxide. The effects of experimental conditions such as temperature, reaction time, and concentration of glucose in the feed on formation of hydrogen product were investigated. Experimental hydrogen yields as high as 12 mol of H-2/mol of glucose were obtained, which is the stoichiometric limit. The gas yield was sensitive to temperature, residence time, and feed concentration. High yield of H-2 with low CO and CH4 yields were obtained at high reaction temperature and low glucose concentrations. Tar formation was observed at high glucose concentrations (> 5 wt %). The catalytic conversion of glucose with ruthenium catalyst in supercritical water is an effective method for hydrogen production directly at a high pressure, which can be extended to other biomass materials. A reaction mechanism for catalytic reforming in supercritical water is also discussed.