Application of Combined Catalyst/Sorbent on Hydrogen Generation from Biomass Gasification

Air-blown gasification of biomass in fluidized bed reactors produces relatively low concentrations of hydrogen. The combination of a catalyst and calcium-based sorbent is being developed to increase the efficiency of converting producer gas from biomass gasification into hydrogen. The conversion process entails reforming the methane and tar, and converting carbon monoxide into hydrogen by the water-gas-shift reaction. The desired material is made in the form of small spherical pellets having a layered structure such that each pellet consists of a highly reactive lime core enclosed within a porous but strong protective shell made of alumina on which a nickel catalyst is loaded. The material serves two functions in catalyzing the reaction of hydrocarbons or carbon monoxide with steam to produce hydrogen while simultaneously absorbing carbon dioxide formed by the reaction. The in-situ removal of CO2 shifts the equilibrium of the steam reforming reaction and/or water gas shift reaction to increase the hydrogen concentration and simultaneously decreases the concentration of carbon oxides in the producer gas stream. The effects of other reaction conditions on the conversion of CH4 and CO have also been investigated and will be presented. In addition, the results of the steam reforming of toluene in the presence of the combined catalyst/sorbent will be described since the compound is considered model for the tars produced by gasifying biomass. Finally, the results of several measures taken to improve the performance of the catalyst/sorbent will be discussed.