(401f) Hydrogen Production from Glucose Using Ru/Al2O3 Catalyst in Supercritical Water

Reforming of lignocellulosic biomass has been identified as a carbon-neutral approach for producing renewable hydrogen. Supercritical water is an environmentally friendly reaction medium and is well known from a variety of applications. At supercritical conditions (above 374 °C and 221 bar), water has liquid-like density and gas-like transport properties, and behaves entirely different than the normal water. This paper deals with the production of hydrogen from glucose which is taken as a model compound for biomass materials. The continuous reforming reaction is carried out in supercritical H2O using a tubular reactor (0.5 m long, 0.250? OD and 0.125? ID) made of Inconel 600. Experiments were conducted to study the effects of the temperature (650-800 oC), residence time (1-7 seconds), and glucose concentration (1-5 wt%) in the feed on the H2 yield, at 241 bar. Incorporation of Ru/Al2O3 catalyst significantly improved the hydrogen yield compared to thermal reforming with some catalysis from the reactor wall. Excellent hydrogen yield near it theoretical maximum of 12 moles of hydrogen /mole of glucose, was achieved. The hydrogen yield decreases with a decrease in the temperature, accompanied by the increase in carbon monoxide formation. At higher glucose concentration (>5 wt%) in the feed, formation of some tar is observed. The investigations revealed that the suppression of methane during the production of H2 from glucose can be achieved by operation at an optimum (short) residence time by having a smaller reactor length or a high feed flow rate. The catalytic reforming of glucose with alumina supported ruthenium catalyst in supercritical water is an effective method to produce hydrogen directly at high pressures.