Concurrent and modulated separation of CO₂ and O₂ by a fluorite/perovskite-based membrane

In this paper, it is reported the fabrication of a new dense ceramic-molten carbonate membrane used for the selective separation of carbon dioxide (CO₂) and oxygen (O₂) at elevated temperatures (850-950°C). First, it was chemically synthesized a fluorite/perovskite ceramic oxide with mixed ionic-electronic conduction properties and general formula Ce_0.9Pr_0.1O_2-δ/Pr_0.6Sr_0.4Fe_0.5Co_0.5O_3-δ (CP-PSFC, 60:40 wt%) by the citrate-ethylene-diamine-tetra acetic acid (EDTA) route. Then, a disk-shaped porous ceramic support partially sintered was infiltrated with a ternary mixture of molten salts of Li₂CO₃/Na₂CO₃/K₂CO₃ composition. The permeation measurements at high temperatures suggest a concurrent separation of both species CO₂ and O₂. The system exhibits high permeance of CO₂ and O₂ by rising to maximum values of 2.17 × 10⁻⁷ and 0.69 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹, respectively at 950°C. Moreover, the possibility of modulating the permeate CO₂:O₂ ratio is envisaged by changing the fluorite to perovskite proportion in the membrane composition. The stability performance of the obtained membrane was studied under a long-term permeation test. It exhibits a remarkable thermal and chemical stability during 110 h at 875°C. This way, it corroborated the proposed new ceramic phase's excellent properties for the fabrication of supported ceramic-molten carbonate membranes.