Hydrogen production by supercritical water gasification of biomass with homogeneous and heterogeneous catalyst

Biomass gasification in supercritical water is a clean and efficient way to convert biomass to hydrogen-rich gaseous products. Appropriate catalyst can lower the reaction temperature to guarantee the technological and economic feasibility. This paper selects Ca(OH)₂, Na₂CO ₃, K₂CO₃, NaOH, KOH, LiOH, and ZnCl₂ as typical homogeneous catalysts and three kinds of Raney-Ni, dolomite, and olivine as typical heterogeneous catalysts. The catalyst effects are investigated in the process of biomass gasification in supercritical water with the temperature of 400°C, pressure of 22 ∼ 24 MPa, and residence time of 20 min. The experimental results show that Raney-Ni has the best hydrogen selectivity and hydrogen yield. The mixture of NaOH with Raney-Ni was investigated in order to research the synergistic effect of different catalysts. The experimental results show that Raney-Ni and NaOH have a synergistic effect in the biomass gasification in supercritical water.