Due to the limited lifetime of fossil fuels and recent concerns about climate change it is imperative to develop efficient processes to produce carbon neutral fuels, such as hydrogen, from renewable energy carriers. Here, a modified chemical looping combustion (CLC) process that relies on a redox cycle of iron oxide to produce a pure stream of H2 from a synthesis gas obtaining via the gasification of biomass is studied. A disadvantage of iron oxide is its poor reactivity with methane, that is, however, a typical component of biomass derived synthesis gas. This characteristic would result in a low fuel conversion of the envisaged process. In this work, we propose to increase the reactivity of Fe2O3-based oxygen carriers with methane by using bimetallic oxygen carriers that contain both Fe2O3 and CuO. Two different oxygen carriers, viz. Fe2O3/MgAl2O4 (70/30 wt. %) and Fe2O3/CuO/MgAl2O4 (70/20/10 wt. %) were synthesized using a high temperature co-precipitation method. The synthesized oxygen carriers were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), and X-ray absorption spectroscopy (XAS). The redox characteristics of the synthesized oxygen carriers were evaluated at 900 �C in a laboratory scale fluidized bed reactor using a mixture of 10 vol. % CH4 in N2 as the fuel. High and stable methane conversions were observed for the MgAl2O4-supported, Fe2O3-CuO-based oxygen carrier. XAS analysis revealed that the presence of Cu enhanced the reduction rates of Fe2O3 and Fe3O4. Furthermore, Cu seems to also prevent the simultaneous reduction of Fe3O4and FeO. These finding have important consequences with regards to the design and numerical modelling of the proposed process.

X-ray spectroscopy (XAS) studies of Fe-Cu based oxygen carriers for a chemical looping based hydrogen production cycle

248th National Meeting (2014)

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