Sorption enhanced catalytic steam gasification process: a direct route from lignocellulosic biomass to high purity hydrogen

We report for the first time on the one-stage production of high purity hydrogen from raw solid lignocellulosic biomass by sorption enhanced catalytic steam gasification (SECSG) in a combined downdraft flow fluidized bed and fixed bed reactor. A Pd/Co-Ni catalyst derived from a hydrotalcite-like material (HT) and dolomite as a CO2 acceptor are fed together with a biomass (chestnut wood sawdust) as the reactor feed. Almost pure hydrogen (>99.9 vol%) and high H-2 yields (up to 90%) can be achieved by this process, which combines conventional gasification/steam reforming, water-gas shift (WGS) reaction and H-2 separation by CO2 capture in one step. The in situ removal of CO2 by the carbonation reaction of dolomite shifts the equilibrium of steam reforming and WGS reactions towards H-2 production. The hydrotalcite derived Pd/Co-Ni catalyst has shown high activity in the cleavage of C-C and C-H bonds during the conversion of tars and hydrocarbons resulting from fast pyrolysis and catalytic steam gasification (CSG), as a result of which further char formation is reduced. The catalyst, which does not require pre-reduction, has shown a good activity and stability after several reaction-regeneration cycles.