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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/Al 2 O 3 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 CH 4 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.

Supercritical water is a promising reforming media for the direct production of hydrogen at high pressures with a short reaction time. In addition to being a dense solvent, supercritical water also participates in reforming reaction. In this work, high-pressure hydrogen is produced from ethanol by reforming over a Ru/Al 2 O 3 catalyst with low methane and carbon monoxide formation. Experiments were conducted in a continuous tubular reactor to study the effects of temperature, pressure, residence time, and water-to-carbon ratio on the H 2 yield. Hydrogen formation is favored at high temperature and at high water-to-ethanol ratio. The formation of methane can be suppressed by operating at an optimal residence time, high reactor temperature, and a low feed concentration of ethanol. Excellent conversion in reaction time as short as 4 s is achieved. Pressure has a negligible effect on hydrogen yield above the critical pressure, and for less than 10 wt % ethanol concentration in the feed, there was negligible coke formation. On the basis of the products obtained, a reaction mechanism is discussed. An activation energy of 65.3 kJ mol -1 was observed.

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