Alkali-thermal gasification and hydrogen generation potential of biomass

Abstract

Generating hydrogen gas from biomass is one approach to lowering dependencies on fossil fuels for energy and chemical feedstock, as well as reducing greenhouse gas emissions. Using both equilibrium simulations and batch experiments with NaOH as a model alkaline, this study established the technical feasibility of converting various biomasses (e.g., glucose, cellulose, xylan and lignin) into H₂-rich gas via catalyst-free, alkali-thermal gasification at moderate temperatures (as low as 300 °C). This process could produce more H₂ with less carbon-containing gases in the product than other comparable methods. It was shown that alkali-thermal gasification follows{\mathrm{C}}_x{\mathrm{H}}_y{\mathrm{O}}_z+\mathrm{2}x\mathrm{NaOH}+(x-z{\mathrm{)H}}_2\mathrm{O}= \mathrm{(2}x+y/\mathrm{2}-z{\mathrm{)H}}_2+x{\mathrm{Na}}_2{\mathrm{CO}}_3, with carbonate being the solid product which is different from the one suggested in the literature. Moreover, the concept of hydrogen generation potential (H₂-GP)—the maximum amount of H₂ that a biomass can yield, was introduced. For a given biomass C_xH_yO_z, the H₂-GP would be moles of H₂. It was demonstrated experimentally that the H₂-GP was achievable by adjusting the amounts of H₂O and NaOH, temperature and pressure.

Graphical abstract

Keywords

hydrogen generation potential / biomass / lignocellulose / alkali-thermal gasification / sodium hydroxide

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg