High carbon dioxide solubilities in trihexyltetradecylphosphonium-based ionic liquids


Due to the potential of ionic liquids for industrial application in CO(2) capture and gas separation processes, solubility of near or supercritical CO(2) in ionic liquids has been object of extensive research during the last few years. This work studies the solubility of CO(2) in phosphonium-based ionic liquids that, unlike imidazolium-based ILs, have received little attention in spite of their interesting characteristics. This work addresses the study of the gas-liquid equilibrium of two ionic liquids, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium chloride, in a wide range of temperatures, pressures, showing that phosphonium ionic liquids can dissolve even larger amounts of CO(2) (on a molar fraction basis) than the corresponding imidazolium-based ILs. In particular trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide seems to be the IL with the largest CO(2) sorption capacity reported up to present, revealing the potential of phosphonium-based ILs for CO(2) capture. A thermodynamic model based on the Peng-Robinson equation of state with the Wong-Sandler mixing rule, using the UNIQUAC model for the activity coefficients, was here adopted to describe the experimental data and for the estimation of the Henry's constants. A universal correlation, for the description of the solubility of CO(2) in ILs previously proposed by us was also applied to the description of the data here measured showing a good agreement with the experimental data. (C) 2010 Elsevier B.V. All rights reserved.



subject category

Chemistry; Engineering


Carvalho, PJ; Alvarez, VH; Marrucho, IM; Aznar, M; Coutinho, JAP

our authors


The authors are thankful for financial support from Fundacao para a Ciencia e a Tecnologia (Project PTDC/EQU-FTT/102166/2008) and PhD grant (SFRH/BD/41562/2007) of Pedro J. Carvalho. The authors would like to acknowledge FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo), process #2006/037111.; M. Aznar is the recipient of a CNPq fellowship.; The authors are thankful for the ionic liquid samples supplied by Cytec.

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