Electrifying Ba0.5Sr0.5Co0.8Fe0.2O3−δ for focalized heating in oxygen transport membranes

Abstract

Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources, especially biomass and solar/wind electricity. In the case of pure oxygen production, oxygen transport membranes (OTMs) appear as an alternative technology for the cryogenic distillation of air, the industrially-established process of producing oxygen. Moreover, OTMs could provide oxygen from different sources (air, water, CO2, etc.), and they are more flexible in adapting to current processes, producing oxygen at 700–1000 °C. Furthermore, OTMs can be integrated into catalytic membrane reactors, providing new pathways for different processes. The first part of this study was focused on electrification on a traditional OTM material (Ba0.5Sr0.5Co0.8Fe0.2O3−δ), imposing different electric currents/voltages along a capillary membrane. Thanks to the emerging Joule effect, the membrane-surface temperature and the associated O2 permeation flux could be adjusted. Here, the OTM is electrically and locally heated and reaches 900 °C on the surface, whereas the surrounding of the membrane was maintained at 650 °C. The O2 permeation flux reached for the electrified membranes was ∼3.7 NmL min−1 cm−2, corresponding to the flux obtained with an OTM non-electrified at 900 °C. The influence of depositing a porous Ce0.8Tb0.2O2−δ catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures (830 °C) were detected at the same imposed electric power. Finally, the electrification concept was demonstrated in a catalytic membrane reactor (CMR) where the oxidative dehydrogenation of ethane (ODHE) was carried out. ODHE reaction is very sensitive to temperature, and here, we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O2 injection into the reaction can be easily fine-tuned.