Chemical looping represents a novel, alternative strategy for fossil fuel conversion. In chemical looping, carbonaceous fuels are converted by an oxygen carrier particle in reduction and oxidation (redox) steps. The oxygen carrier is essential to chemical looping reactions as it affects the products, the rate of reaction, and the stability of the catalyst. Its selection and optimization is of utmost importance in chemical looping fuel conversion processes. The presence of a support in the oxygen carrier can improve the reactivity and long term stability without directly participating in the chemical looping reaction. Perovskites, which can be active for chemical looping gasification, are promising for use as oxygen carrier supports, but they have limited oxygen storage capacity. In the present work, we attempt to improve iron-based oxygen carriers by incorporating mixed ionic-electronic conductive (MIEC) perovskite supports. We propose that MIEC supports facilitate countercurrent conduction of O2- and electrons, allowing facile O2- transport to and from the iron oxide. It is also proposed that MIECs can be used efficiently in redox catalyst for methane conversion by embedding iron oxide particles in a MIEC shell (LSF@Fe2O3). The present study investigates the use of LSF, a mixed-conductor, to enhance the performance of iron-based oxygen carriers for methane conversion. The LSF enhanced oxygen carriers exhibit around one order of magnitude higher reactivity compared to a TiO2 supported reference oxygen carrier. The improved oxygen carriers show excellent recyclability and good resistance towards coke formation for CH4 conversion. The LSF@Fe2O3 core-shell material not only has excellent conversion activity, but resists coking, even after full reduction, and it is highly stable. The high methane conversion performance of the LSF containing redox catalyst likely results from mixed conduction, allowing facile lattice oxygen transport from finely divided iron oxide particles to the partial surface.

Mixed-conductor redox catalyst for fuel conversion

247th National Meeting (2014)

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