Hydrogen production by chemical looping steam reforming of methane over Mg promoted iron oxygen carrier: Optimization using design of experiments

In the chemical looping reforming (CLR) process, methane is converted to hydrogen and carbon monoxide through cyclic reduction-oxidation reactions of fuel with active lattice oxygen (O2-) of an oxygen carrier. In this research, Mg promoted iron based oxygen carrier was used in the process. The response surface method (RSM) based on Box-Behnken design was applied to examine the operating conditions of chemical looping steam methane reforming process. Independent variables including reaction temperature (550-750 degrees C), Mg loading (0-10%) and oxygen carrier preparation method (co-impregnation and sequential impregnation methods) were selected for investigation and optimization of methane conversion, hydrogen production yield and CO/CO2 molar ratio using RSM. The characterization of samples was accomplished by means of X-ray diffraction (XRD), N-2 adsorption-desorption (BET test) and transmission electron microscope (TEM). The Design expert software suggested several optimized solutions; among them, the best choice was 15Fe/5Mg/Al2O3 oxygen carrier synthesized with sequential impregnation method at reaction temperature of 650 degrees C. However, 15Fe/5Mg/Al2O3 oxygen carrier is consistently stable in chemical looping reforming with high hydrogen producing capacity over redox cycles. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.