Exothermic hydrogen production system in supercritical water from biomass and usual domestic wastes with an exploitation of RuO₂ catalyst

This paper deals with a method of producing hydrogen from biomass and sewage disposals in supercritical water by use of ruthenium dioxides as a catalyst. Experiments were carried out under argon atmosphere with a batch reactor made of INCONEL625. Reaction temperatures and pressures were changed in the ranges of 400-500 °C and 30-50 MPa, respectively. The gas produced was quantitatively analyzed by on-line gas chromatography. In conclusion, considerably high ratios of hydrogen up to 38.5% were produced from the sewage disposals. This value was even higher than the hydrogen production ratios from other biomass: 15.0% from cellulose, 14.1% from pulp, 16.0% from waste paper, and 27.0% from paper sludge. The heat balance was calculated in the present reaction system using ruthenium oxide as the catalyst in supercritical water for the reaction of naphthalene and cellulose. The result showed that the total reaction was exothermic. This is rather surprising, because most of the hydrogen forming reactions are endothermic. The present result should be due to the excess heat derived by the partial formation of carbon dioxide.