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 H2 yields (up to 90%) can be achieved by this process, which combines conventional gasification/steam reforming, water-gas shift (WGS) reaction and H2 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 H2 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.