Preparation of double perovskite-type oxide LaSrFeCoO6 for chemical looping steam methane reforming to produce syngas and hydrogen

Abstract

Double-perovskite type oxide LaSrFeCoO6 was used as oxygen carrier for chemical looping steam methane reforming (CL-SMR) due to its unique structure and reactivity. Solid-phase, amorphous alloy, sol-gel and micro-emulsion methods were used to prepare the LaSrFeCoO6 samples, and the as-prepared samples were characterized by means of X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area. Results showed that the samples made by the four different methods exhibited pure crystalline perovskite structure. The ordered double perovskite LaSrFeCoO6 was regarded as a regular arrangement of alternating FeO6 and CoO6 corner-shared octahedra, with La and Sr cations occupying the voids in between the octahedral. Because the La3+ and Sr2+ ions in A-site did not take part in reaction, the TPR patterns showed the reductive properties of the B-site metals. The reduction peaks at low temperature revealed the reduction of adsorbed oxygen on surface and combined with the reduction of Co3+ to Co2+ and to Co0, while the reduction of Fe3+ to Fe2+ and the partial reduction of Fe2+ to Fe0 occurred at higher temperatures. From the point of view of the oxygen-donation ability, resistance to carbon formation, as well as hydrogen generation capacity, the sample made by micro-emulsion method exhibited the best reactivity. Its redox reactivity was very stable in ten successive cycles without deactivation. Compared to the single perovskite-type oxides LaFeO3 and LaCoO3, the double perovskite LaSrFeCoO6 exhibited better syngas and hydrogen generation capacity.