Hydrogen rich gas production from pyrolysis-gasification of biomass with combined catalyst and sorbent

Abstract

In this work, the hydrogen production during biomass steam pyrolysis-gasification with a combined catalysts and sorbent (catalyst/sorbents) was studied in a drop tube two-stages fixed bed reactor. The catalyst/sorbents were prepared by an excess-solution impregnation method. A nickel oxide (NiO)/magnesium oxide (MgO)/calcium oxide(CaO) catalyst/sorbents containing 10 wt. % NiO, 5 wt. % MgO and 5 wt. % CaO on gamma alumina (γ-Al2O3) showed the best activity in sorption enhanced hydrogen production (SEHP) for the pyrolysis-gasification of sugarcane leaves. Besides, the highest H2 concentration and the lowest CO2 concentration were attained using the Mg5Ni10Ca5 catalyst/sorbents. Because Mg5Ni10Ca5 catalyst/sorbents provided the dominant phases of CaO which can increase the CO2 adsorption capacity to promote the H2 production. Moreover, the synergistic effect between CaO and MgO sorbents which were prepared by dry- and wet-physical mixing with different molar ratios were investigated. The results indicated that the wet-mixed sorbent with the molar ratio between CaO and MgO of 2:1 (WM 2:1) afforded a higher H2 yield because the Ca(OH)2 phases in the wet-mixed sorbents induced high performance for SEHP. Furthermore, the devolatilization and gasification temperature of 600 oC gave the optimal condition for SEHP. The effect of NiO loading content on WM(2:1) was also examined for the H2 production. The results showed that NiO 5 wt.% on WM (2:1) sorbents showed the optimal yield and concentration of H2. The obtained results will be useful for the effective development of combined catalyst/sorbents for SEHP of biomass pyrolysis-gasification