Performance of CeO2-Modified Iron-Based Oxygen Carrier in the Chemical Looping Hydrogen Generation Process

The iron-based oxygen carrier with high oxygen transfer capacity has always been the key point in the chemical looping hydrogen generation (CLHG) process. In this study, CeO2-modified iron-based oxygen carriers with the porous reticular structure were prepared by the sol-gel method. Samples were tested in a thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor, respectively, to evaluate their capacities of hydrogen production and the resistance to carbon deposition or Fe3C formation. The effects of preparation conditions (CeO2 loading and [C6H8O7 center dot H2O]/[PEG400] molar ratio) and experimental conditions (reducing atmosphere and temperature) on the physicochemical properties of CeO2-modified iron-based oxygen carriers were investigated. The initial screening test in TGA was done to select the samples with excellent reducibility and strong resistance to carbon deposition or Fe3C formation. Subsequent tests in the fixed-bed reactor were conducted to evaluate the redox characteristics and cyclic performance of the selected CeO2-modified samples. The results confirmed that iron-based oxygen carriers modified by CeO2 could effectively inhibit carbon deposition or Fe3C formation and the oxygen carrier prepared under the preparation conditions of Fe2O3/CeO2/Al2O3 = 65/5/30 and C6H8O7 center dot H2O/PEG400 = 3 stood out from all the candidates by virtue of its high hydrogen production efficiency and the excellent recycle ability in the CLHG process. The oxygen carriers at the optimal reducing atmosphere (CO/H-2/N-2 = 40/30/30 and the steam oxidation reaction at 900 degrees C) showed the best performance with the highest hydrogen yield.