CO₂/C2h6 separation using solubility selective membrane materials

CO₂ is an impurity which must be removed from natural gas streams in a process commonly known as natural gas conditioning. The effectiveness of membranes to break the carbon dioxide/ethane azeotrope was studied. Membrane technology was successfully implemented in natural gas processing facilities and was effective in separating CO₂ from methane. The membrane material selected to break the CO₂/ethane azeotrope should have a high CO₂/ethane selectivity and high CO₂ permeability. Mixed gas permeation experiments were conducted using a gas mixture containing 45.3 mole % CO₂ and the balance ethane. The mixed gas results show CO₂ strongly plasticizes crosslinked poly(ethylene oxide) films at lower temperatures. Slight plasticization of the film is observed at 283 and 308K. CO₂ plasticization decreases the mixed gas CO₂/ethane selectivity, relative to pure gas values, because the ethane permeability is enhanced by the plasticization effects of CO₂. The mixed gas selectivity increases as temperature decreases. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).