(63d) High-Temperature Carbon-Dioxide Perm-Selective Membranes

The only high-temperature carbon-dioxide (CO₂) perm-selective membranes are dense ceramic-carbonate dual-phase membranes consisting of an oxygen ionic-conducting metal-oxide ceramic phase and a molten metal-carbonate phase. At high temperatures (>500^oC), CO₂ can transport as the carbonate ion through the metal-carbonate phase at a sufficiently high rate under the driving force of the CO₂ partial pressure gradient, balanced by the counter-diffusion of oxygen ions in the ceramic phase. This results in a net flux of neutral CO₂ molecules through the membrane, prohibiting transport of other gases. Therefore, the dense ceramic-carbonate membrane provides theoretically infinite selectivity for CO₂. As the only group of membranes perm-selective to CO₂ at high temperatures, the ceramic-carbonate membranes are attractive for a number of CO₂-related separation and reaction processes for hydrogen production, CO₂ capture and electric power generation. This paper will provide a brief overview of key concept, material/structure properties and CO₂ permeation characteristics of the ceramic-carbonate membranes. It will present latest results of several C1 conversion reactions on the ceramic-carbonate membrane reactors with controlled addition or removal of CO₂ from the membrane reactor to enhance reaction and achieve reactant/product separation.