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 Ce0.8Sm0.2O1.9 (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.