Asymmetric thin samarium doped cerium oxide-carbonate dual-phase membrane for carbon dioxide separation

Samarium doped ceria (SDC)-carbonate dual-phase membranes are permselective to carbon dioxide. This paper reports a method to prepare thin SDC-carbonate membranes on an adequate base support to improve CO₂ permeance of the membranes. It was found that macroporous support made of a physical mixture of SDC and 40 vol % bismuth-yttrium-samarium oxide (BYS) has the desired pore structure, ionic conductivity, carbonate nonwettability, and mechanical compatibility with the thin SDC-carbonate membrane layer. Asymmetric porous supports consisting of a thin, porous SDC top layer on an SDC-BYS base were prepared by the copressing method. The porous SDC top layer was filled with molten carbonate by the direct infiltration method. The final membranes consist of a 150 μm, hermetic SDC-carbonate layer on the macroporos SDC-BYS base support. The thin SDC-carbonate dual-phase membrane offers significantly improved CO₂ permeance as compared to thick SDC-carbonate membranes. Both membrane thickness and the structure of the SDC phase affect CO₂ permeance. The thin SDC-carbonate membranes exhibit CO₂ flux of 1.33 × 10^-3-6.55 × 10^-3 mol/s/m² at 550-700 °C, with steady state operation for at least 160 h. The CO ₂ permeation flux is related to upstream and downstream CO ₂ partial pressures by a power law, consistent with the theoretical model.