Ionic liquids for chloromethane/isobutane distillative separation: Express screening

Abstract

The present study centres on room-temperature ionic liquids (ILs) as entrainers in extractive distillation of chloromethane/isobutane mixtures. The binary system, chloromethane/isobutene, is an azeotropic system. In this study, IL entrai-ners are shown to be able to break the azeotrope and, thus, assure the separation in the whole range of chloromethane/isobutane ratios. ILs formed from different cations and anions are considered and their influence on chloromethane/isobu-tane separation is explored. Among the ILs studied, those containing the trifluor-omethanesulfonate ([CF3SO3]-) or tricyanomethanide ([C(CN)3]-) anion are demonstrated to exhibit an enhanced potential for chloromethane/isobutane separation compared to the corresponding ILs based on the bis(trifluoromethyl-sulfonyl)imide ([Tf2N]-) anion. Moreover, the ILs enclosing these anions are cheaper than those with the [Tf2N]- anion. Thus, the separation ability, solubility of chloromethane/isobutane mixtures, and costs of IL entrainers can be adjusted by the right choice of cations and anions. © 2010 WILEY-VCH Verlag GmbH & Co.