Catalytic Consequence of Oxygen of Lanthanum Ferrite Perovskite in Chemical Looping Reforming of Methane

Abstract

LaFeO3 perovskites were prepared by solution combustion method using Dextro d-(−) Levo-(+) tartaric acid as a complexing agent. Characterization by different techniques such as X-ray diffraction, Brunauer−Emmett−Teller surface area, and scanning electron microscopy revealed relatively small crystals of perovskites. A relatively high capacity of reversible oxygen storage (3 mmol/gcat) of LaFeO3 has been evidenced. High activity and high selectivity to synthesis gas make LaFeO3 attractive as a catalyst and oxygen carrier for methane partial oxidation by the chemical looping process. The study of the reaction rate as function of oxygen site coverage reveals a kinetic relevant step in methane partial oxidation involving a pair of surface oxygen and oxygen vacancy. Removal of lattice oxygen generated vacancy sites which increase the reaction rate at relatively high oxygen concentrations, while the availability of surface oxygen determines the reaction rate at relatively low surface oxygen concentrations. The surface adsorbed oxygen is highly active to complete combustion while the lattice oxygen is very selective to synthesis gas.