Composite electrolyte membranes for high temperature CO2 separation

A membrane device that can selectively separate CO2 at temperatures exceeding 600 °C has been demonstrated. The membrane can be made from a composite material made of a molten carbonate electrolyte that fills the pore space in a solid oxide electrolyte (e.g. yttria doped zirconia (YSZ), or gadolinia doped ceria (CGO)). The experimental evidence points to a transport mechanism based on opposing ionic currents of carbonate and oxide ions. The flux of CO2 across these membranes has been shown to increase with temperature, reaching permeabilities of 10−11 mol m−1 s−1 Pa−1 (or permeance of 3 × 10−8 mol m−2 s−1 Pa−1) at 850 °C. The use of a non-ion conducting solid oxide, Al2O3, does not result in strong CO2 permeability or selectivity, supporting a facilitated dual-ion transport mechanism.

Research highlights▶ High temperature (>650 °C) CO2 separation with dual-ion membrane. ▶ Selective CO2 permeability achieved over 165 h of operation. ▶ CO2 transport requires an oxide conducting phase (e.g. YSZ, CGO). ▶ CO2 transport can occur with or without reactivity between the phases.