Calcium promoted Fe/Al2O3 oxygen carrier for hydrogen production via cyclic chemical looping steam methane reforming process

Abstract

Chemical-looping steam methane reforming (CL-SMR) is known as an innovated method for the generation of high purity H2 or synthesis gas. This process is based on reduction–oxidation cycles through a gas–solid reaction with a catalyst as oxygen carrier. In this study, the effect of Fe metal loading in Fe/Al2O3 oxygen carrier and its preparation method were investigated in CL-SMR process under different reaction temperatures of 550–800 °C. The results revealed that 15 wt.%Fe/γ-Al2O3 oxygen carrier synthesized by an impregnation method has the best activity in this process. Afterwards, the effect of calcium promoter on the performance of optimized oxygen carrier (15 wt.%Fe/γ-Al2O3) was studied via various impregnation methods. The results showed 15 wt.%Fe–5 wt.%Ca/γ-Al2O3 oxygen carrier synthesized by co-impregnation method exhibited the highest catalytic activity of 100% methane conversion and 83% hydrogen production yield at a low temperature of about 700 °C. Moreover, this oxygen carrier revealed the maximum methane conversion and the lowest activity reduction during 17 oxidation–reduction cycles between the other samples. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) analysis, and BET techniques.