Sequential hydrothermal gasification of biomass to hydrogen

A new technology, in which a renewable biomass is used to produce hydrogen fuel, is described. This hydrogen can be used as a feed for fuel cells to generate electricity or in other energy-producing processes. Degradation and gasification of cellulose-based biomass in compressed water was studied in the 100–400 °C temperature range. Phase behavior of the cellulose in subcritical water was studied in a diamond-anvil cell, coupled with optical microscopy, at heating rates of 1 and 5 °C/s. Homogeneous conditions of a single water-cellulose phase were established. Complete dissolution of the cellulose was achieved at 333 °C. The evolution mechanism based on a rapid hydrolysis of the cellulose to oligomers and glucose is suggested. Glucose was then used as a model compound to characterize the chemistry of biomass gasification. A 0.1-M glucose solution was fed into a continuous-flow reactor at a pressure of 100 bar using an HPLC pump. Catalytic effects of Pt/Al₂O₃ on the gasification temperature were determined. Gas product composition was analyzed using online GC-TCD. A mixture of H₂, CO₂, and CH₄ gas was produced. Quantitative analysis of the total organic carbon in the liquid residue indicated 67% carbon gasification efficiency at 330 °C. Qualitative analyses of liquid residues showed that the main decomposition products in the liquid phase were alcohols and carboxylic acids. It was shown that the hydrogen fuel could be efficiently generated from biomass.