Carbon dioxide permeation through ceramic-carbonate dual-phase membrane-effects of sulfur dioxide

CO₂ perm-selective ceramic/carbonate dual phase membranes are promising in a number of high temperature separation and reaction processes for CO₂ capture or process intensification. The stability of these membranes in gas containing SO₂ is important for their applications dealing with sulfur containing stream. The present work studies gas permeation performance and stability of Ce_0.8Sm_0.2O_1.9 (SDC)/Li₂CO₃-Na₂CO₃ membrane in SO₂ containing gas. During CO₂ permeation through the SDC/carbonate membrane with feed gas containing SO₂, the CO₂ permeation flux decreases with on-stream time and the decrease rate increases with the SO₂ concentration in the feed gas. The SDC phase remains unchanged after exposure to SO₂ containing gas, but the SO₂ exposure of the SDC-carbonate dual phase membrane results in formation of sulfate in the carbonate phase in the membrane. The sulfate content in the molten salt phase increases with SO₂ concentration in the gas or exposure time. CO₂ permeation flux through SDC/carbonate-sulfate dual phase membranes prepared in this work decreases with the increase of the sulfate content in the molten salt phase. The formation of sulfate in the carbonate phase lowers carbonate ion conductivity which becomes the dominant step causing a reduction in CO₂ permeance.