A novel study of sulfur-resistance for CO ₂ separation through asymmetric ceramic-carbonate dual-phase membrane at high temperature

Sulfur compounds present in high-temperature gases from various industrial sources have a negative influence on the permeability of different kinds of membranes. In this study, we present a general and efficient strategy to design and prepare two asymmetric membranes for CO ₂ separation that are resistant to H ₂ S. The asymmetric membranes, mainly composed of one adsorbed layer for H ₂ S consumption and one dense ceramic-carbonate layer for CO ₂ separation, show not only high CO ₂ permeation flux but also remarkably stable permeation behavior under an H ₂ S-containing atmosphere. The sulfur-resistant stability times of the asymmetric membranes are approximately 10–12 times higher than the single ceramic-carbonate dual-phase membrane. The adsorbed layer of the asymmetric membranes can react with H ₂ S to form Ce-O-S phases, gradually causing deactivation of the adsorbed layer. However, the adsorbed layer can be regenerated in the oxygen-containing gas stream above 850 °C, which can effectively remove the sulfur content from the adsorbed layer, making recycle of the membrane possible. Sulfur accumulated in the adsorbed layer of the membrane as a Ce ₂ O ₂ S phase, can be oxidized into SO ₂ under air stream and elemental sulfur (S) under a 2.5% O ₂ /He gas stream. These asymmetric membranes thus possess high permeation stability in the H ₂ S-containing atmosphere with good regenerability and also have potential in collection and removal of sulfur impurities from gas streams.