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

Abstract

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.