Efficient utilization of Al2O3 as structural promoter of Fe into 2 and 3 steps chemical looping hydrogen process: Pure H2 production from ethanol

Chemical Looping Hydrogen (CLH) allows the direct production of pure hydrogen exploiting the redox properties of Fe, with high flexibility on the type of reductant used. In this work, a highly pure hydrogen stream suitable for the direct use into Proton Exchange membrane Fuel Cells was produced, using bioethanol as renewable fuel. The influence of both redox temperature (675°C–750 °C) and chemical composition of the Fe-based particles (2 wt% and 40 wt% of alumina added) on the carbon formation rate during reduction step was also deeply analyzed. Al2O3 changed both FexOy redox kinetics and equilibrium phases, leading to a complete iron deactivation at high Al2O3 concentration. The addition of an air oxidation step (3 steps CLH) is fundamental to restore the redox activity, with a constant efficiency of about 30% at 750 °C for 10 cycles. Furthermore, Al2O3 promotes the ethanol conversion into carbon, undermining the hydrogen purity.