Role of gas-phase and surface chemistry in methane reforming using a La0.9Ca0.1FeO3-delta oxygen transport membrane

Abstract

This study investigates the performance of a La0.9Ca0.1FeO3-δ (LCF) membrane for applications including oxyfuel combustion, CO2 reuse and syngas production under a reactive environment using methane (CH4)-argon (Ar)-carbon dioxide (CO2) mixtures in the sweep stream. Through experimental measurements, we show that an LCF membrane can act as a catalyst for methane pyrolysis driven by the presence of iron at the B-site of the perovskite structure. Using methane-argon mixtures, the oxygen flux JO2 increases by one order of magnitude compared to the case with no methane. Measurements in the range of 900-950 C suggest that the aforementioned enhancement is related to surface reactions consuming oxygen ions at the membrane surface. However, JO2 levels off when the inlet CH4 mole fraction reaches approximately 5%. The same applies for methane conversion. Addition of CO2 into the sweep stream has a significant impact on JO2 rise and syngas production. As more CO2 is added, surface carbon monoxide (CO) and hydrogen (H2) mole fractions increase by an order of magnitude. The high yield of syngas at the membrane surface results in a higher JO2 as more reactants participate in heterogeneous reactions with oxygen ions; methane conversion reaches approximately 100% showing that dry reforming (in the gas-phase) plays an important role. This oxygen flux enhancement is accompanied by significant reuse of CO2. The proposed technology can have a major impact on the CO2 recycle and the effort to mitigate its accumulation in the atmosphere.