Hydrogen production by gasification of Kenaf under subcritical liquid‒vapor phase conditions

Abstract

In this study, Kenaf biomass was gasified under subcritical liquid-vapor conditions and effect of initial water amount on gas composition and hydrogen production was evaluated at different temperatures. Gasification was carried out in a batch type reactor, with various initial water volumes (0, 12, 25, 50, 75 mL), at different temperatures (250, 275, 300, 325 °C) and with different catalysts (Ru/C, Pt/C, Na2CO3, Fe2O3, CaO, CaCO3 and RuCl3). The results revealed that the gasification efficiency and hydrogen selectivity are dramatically varied with initial water percentage that was fed to the reactor. The gaseous products obtained from hydrothermal gasification of kenaf were mainly H2, CO2, and in lower but varying amounts, CH4 and C2H4. Water soluble RuCl3 was found to be more effective than water insoluble Ru/C catalyst on biomass gasification. RuCl3 catalyst has a high catalytic activity for kenaf gasification with greater H2 selectivity. Maximum total gas (462.5 mL) and H2 mole fraction in the gaseous product (44.5%) were obtained at 250 °C with RuCl3 catalyst. The maximum carbon conversion (%) was also obtained with RuCl3 as 71.3%. Water behaves as both the reaction medium and the second main reactant beside biomass, during the subcritical liquid-vapor phase gasification process.