CO₂ permeation through asymmetric thin tubular ceramic-carbonate dual-phase membranes

Ceramic-carbonate dual-phase dense membrane is a promising high temperature CO₂ separation membrane with remarkable CO₂ permeance and theoretically infinite CO₂ selectivity. This paper reports synthesis and CO₂ permeation properties of asymmetric tubular dual-phase membranes with a thin samarium doped ceria (Ce_0.8Sm_0.2O_1.9, SDC)-carbonate separation layer and a thick porous SDC-Bi_1.5Y_0.3Sm_0.2O_3-δ (BYS) support. The asymmetric tubular thin (0.12 mm) dual-phase membrane has much higher CO₂ permeance and lower activation energy for permeation than the thick (1.0–1.5 mm) membranes. At 900 °C with 50%CO₂/N₂ feed at 1 atm, the CO₂ permeation flux and permeance for the thin membrane reach 1.53 × 10⁻² mol m⁻² s⁻¹ (or 2.05 mL(STP) cm⁻² min⁻¹) and 3.16 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹, respectively, with activation energy for permeation of 62.5 kJ/mol. These dual-phase membranes exhibit slightly higher CO₂ permeance with essentially same activation energy for permeation, and stable operation, for CO₂ permeation with simulated syngas (with the composition of 49.5%CO, 36%CO₂, 4.5%N₂, 10%H₂) feed. The CO₂ permeation fluxes of the tubular asymmetric membranes can be well described by the power-function flux equation. The analysis of CO₂ permeation data with the model shows that the CO₂ separation performance of the tubular asymmetric membranes can be further improved by optimizing the microstructure of ceramic porous supports. This work demonstrates that asymmetric SDC-carbonate dual-phase membrane has high potential for practical application in high temperature CO₂ separation.