Dual-Phase Metal−Carbonate Membrane for High-Temperature Carbon Dioxide Separation

This paper describes a new concept of dense, dual-phase membrane consisting of two phases conducting, respectively, CO 3 2- and electrons for selective permeation of CO 2 and O 2 at high temperatures. Membranes with a molten carbonate phase in a porous stainless-steel support were synthesized by a direct infiltration method. Membrane preparation conditions were optimized to obtain stable, gas-tight dual-phase membranes at high temperatures (>450 °C). The dual-phase membranes exhibit low single-gas permeance for pure CO 2 and N 2 (<5 × 10 -9 mol s -1 m -2 Pa -1 ) in 450−650 °C but substantially higher CO 2 permeance for CO 2 mixed with O 2 at high temperatures. CO 2, after interacting with O 2, transports through the molten carbonate phase in a form of CO 3 2-, with electrons transporting through the porous metal support. With further improvement, the dual-phase membranes may offer application in producing O 2 -enriched CO 2 streams for the oxyfuel combustion process. The concept can be also extended to prepare CO 2 perm-selective dense membranes for high-temperature CO 2 separation.