Novel oxygen-carrier materials for chemical-looping combustion and chemical-looping reforming; LaxSr1-xFeyCo1-yO3-delta perovskites and mixed-metal oxides of NiO, Fe2O3 and Mn3O4

Solid oxygen-carrier materials for chemical-looping applications have been examined by reduction with CH4 and oxidation with air in a fixed-bed quartz reactor at 900 degrees C. Four perovskite materials, three metal-oxide materials and four metal-oxide mixtures have been studied. It was found that LaxSr1-xFeO3-delta perovskites provided very high selectivity towards CO/H-2 and should be well suited for chemical-looping reforming. Substituting La for Sr was found to increase the oxygen capacity of these materials, but reduced the selectivity towards CO/H-2 and the reactivity with CH4. La0.5Sr0.5Fe0.5CO0.5O3-delta was found to be feasible for chemical-looping combustion applications. NiO/MgAl2O4 propagated formation of solid carbon, likely due to the catalytic properties of metallic Ni. Fe2O3/MgAl2O4 had properties that made it interesting both for chemical-looping combustion and chemical-looping reforming. Adding 1% NiO particles to a bed of Fe2O3-particles increased both reactivity with CH4 and selectivity towards CO/H-2 for reforming applications. Mn3O4/Mg-ZrO2 was found to be suitable for chemical-looping combustion applications, but it could not be verified that adding NiO produced any positive effects. (C) 2007 Elsevier Ltd. All rights reserved.