Novel oxygen-carrier materials for chemical-looping combustion and chemical-looping reforming; La xSr 1− xFe yCo 1− yO 3− δ perovskites and mixed-metal oxides of NiO, Fe 2O 3 and Mn 3O 4

Abstract

Solid oxygen-carrier materials for chemical-looping applications have been examined by reduction with CH 4 and oxidation with air in a fixed-bed quartz reactor at 900 °C. Four perovskite materials, three metal-oxide materials and four metal-oxide mixtures have been studied. It was found that La x Sr 1− x FeO 3− δ 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 CH 4. La 0.5Sr 0.5Fe 0.5Co 0.5O 3− δ was found to be feasible for chemical-looping combustion applications. NiO/MgAl 2O 4 propagated formation of solid carbon, likely due to the catalytic properties of metallic Ni. Fe 2O 3/MgAl 2O 4 had properties that made it interesting both for chemical-looping combustion and chemical-looping reforming. Adding 1% NiO particles to a bed of Fe 2O 3-particles increased both reactivity with CH 4 and selectivity towards CO/H 2 for reforming applications. Mn 3O 4/Mg–ZrO 2 was found to be suitable for chemical-looping combustion applications, but it could not be verified that adding NiO produced any positive effects.