Catalytic steam reforming of biomass tar over iron- or nickel-based catalyst supported on calcined scallop shell

Abstract

Calcined scallop shell (CS) exhibits alkaline property with a porous structure, and could be applied for the adsorption and decomposition of biomass-derived tar. In this study, steam reforming of tar derived from pruned apple branch over CS was investigated in a fixed bed at 650°C. It was found that CS had good activity for the steam reforming of tar to produce synthesis gas (syngas), and was able to be recycled. To promote the gas production efficiency, iron or nickel was supported on the CS, and used for the reforming of tar. The effect of heating rate on the gas production rate was investigated, and it was found that reduced iron- or nickel-supported CS showed better activities under the condition of rapid heating. Iron- or nickel-based catalyst in its oxide state was also investigated for the reforming of tar. No catalytic activity was found at the beginning, but good activity appeared after approximately 30min of reaction when the metal oxide was reduced to its metallic form by the initially generated syngas (CO and H2) from the pyrolysis of biomass without the aid of catalyst. Iron and nickel in their metallic forms rather than their oxide ones were considered as active sites for the reforming of tar. Furthermore, the alkaline elements in the biomass, which could enhance the activity of the catalysts, were identified to be accumulated on the surface of the catalysts with the biomass-derived tar. As a result, a larger amount of syngas was produced when the regenerated catalysts were applied. Based on these experimental results, a possible catalytic process was proposed.