CO2 reduction and methane partial oxidation on surface catalyzed La0.9Ca0.1FeO3-δ oxygen transport membranes

Abstract

In this paper, we demonstrate CO 2 thermochemical reduction to CO in a La 0.9 Ca 0.1 FeO 3-d oxygen ion transport membrane reactor. For process intensification, we also show that methane can be used on the sweep side, producing two streams: a CO stream from CO 2 reduction on the feed side, and a syngas stream on the other. We show that surface reactions are the rate-limiting steps for fuel-assisted CO 2 reduction on a flat LCF-91 membrane. To improve productivity, we study how that adding catalytic porous layers can accelerate these steps and hence, increase the CO 2 -to-fuel conversion rates. Adding LCF-91 porous layers onto the membrane surface raised the oxygen flux by 1.4X. Secondly, different catalysts (Ce 0.5 Zr 0.5 O 2 on the feed side and (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3 on the sweep side) were added onto the porous layers to further accelerate the surface reaction rates. As a result, the oxygen flux was further increased especially at lower temperatures, e.g., at 850°C, oxygen flux was raised by one order of magnitude as compared to the unmodified membrane. Process intensification was tested on the latter membrane configuration, and the syngas produced on the sweep side had a H 2 :CO ratio very close to 2, ideal for production of fuels. Carbon species balance showed that higher methane concentration on the sweep side could lead to coke formation. Results also show that the selectivity to CO 2 near the membrane surface is higher than that at the reactor outlet due to the availability of lattice oxygen and the favorable water-gas shift reactions.