Preparation of composite nickel-iron oxide as highly reactive oxygen carrier for chemical-looping combustion process

Chemical-looping combustion (CLC) of fossil fuel has a potential to generate power with achieving the inherent CO2 capture by means of an oxygen carrier (OC) that is circulated between air and fuel reactors. In this article, a composite oxygen carrier with highly redox reactivity for chemical-looping combustion process was first synthesized using nickel nitrate and iron nitrate as precursors in a sol-gel process, respectively. Materials characterization of the prepared OC samples were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurements, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The reactivity of the oxygen carrier in CLC process was evaluated by a thermogravimetric analyzer by alternating methane and air. The prepared nickel-iron composites oxygen carrier exhibited excellent oxygen-transfer capability both in the fuel and air reactors than pure Fe2O3, NiO, NiFe2O4, and physically mixed Fe2O3-NiO samples. The synergistic effect between Fe and Ni cations can enhance the reduction rate of iron oxide; meanwhile, it also improves the oxidation reaction rate of metallic nickel. The different migration behaviours of iron and nickel under the reducing and oxidizing atmospheres were observed by XRD and EDX, respectively. Finally, twenty-cycles of redox reaction demonstrated that composites oxygen carrier loaded on the SiC inert support had excellent redox activity and sintering resistance and consequently was capable of the CLC process.