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8CO 2 is a common constituent of natural gas. Standards for its maximum concentration differ from about 9 2% for pipeline to 50 ppm for liquefaction. All natural gas constituents absorb CO 2 to some degree when 10 in the liquid phase, requiring multi-step natural gas treatment processes. The existence of a minimum-11 boiling temperature azeotrope between ethane and carbon dioxide particularly complicates CO 2 separation. 12Extractive distillation with higher molecular weight hydrocarbons as the solvent represents the most 13 competitive means for the separating CO 2 from ethane. The conventional separation method involves two 14 distillation columns in series and rather high amount of energy. 15This investigation proposes an efficient method for CO 2 -ethane separation that produces all products at high 16 purity with less capital and operating costs in comparison with the conventional system. The new operating 17 flowsheet includes three columns: a CO 2 recovery column, a solvent recovery column, and a concentrator 18 column. The proposed system requires 10 % less total annual cost (TAC) and 16% less energy compared 19 to the conventional system at the same purification. Additionally, unlike the conventional system, the 20 proposed design separates CO 2 in the form of a liquid product, which avoids the high amount of energy 21 required for the liquefaction. Thus, this technology provides a useful alternative towards the less expensive 22 CO 2 -ethane separation process. 23

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