Synthesis of Fe/CaO active sorbent for CO2 absorption and tars removal in biomass gasification

CO2 capture is a strategy to reduce gas emissions from hydrogen production process. Among different materials, CaO has been used for CO2 absorption principally for its abundance and low toxicity giving economical advantage. In this work different Fe/CaO sorbents were prepared using three CaO precursors including CaO, CaCO3 and Ca(CH3COO)2·H2O and two iron salts, Fe(CH3COO)2 and Fe(NO3)3·9H2O. The effect of calcination temperature, CaO precursor, iron salt, and preparation conditions on the physicochemical properties and CO2 absorption capacity were discussed. To characterize the sorbents, various techniques such as XRD, BET and TPR and absorption capacity tests were performed. The most appropriated calcination temperature to obtain CaO phase is 750 °C. The higher BET surface area, observed for sorbents prepared from calcium acetate, is correlated to the higher CO2 absorption capacity. Iron (II) acetate promotes the formation of Fe2O3 phase and iron (III) nitrate leads to the formation of Ca2Fe2O5. The mechanical mixture leads to the formation of Fe2O3 while sol–gel and impregnation methods promote the formation of Ca2Fe2O5. Finally the preparation from mechanical mixture of calcium and iron (II) acetates will be the best compromise between a high CO2 absorption capacity and the presence of Fe0 efficient for the tars reforming.