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Download fileExperimental Measurement of the Solubility and Diffusivity of CO2 in Room-Temperature Ionic Liquids Using a Transient Thin-Liquid-Film Method
journal contribution
posted on 2007-11-21, 00:00 authored by Ying Hou, Ruth E. BaltusIn this paper, results from an experimental investigation of carbon dioxide (CO2) solubility and diffusivity in
the ionic liquids 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([pmmim][Tf2N]), 1-butyl-3-methylpyridinium
bis(trifluoromethyl sulfonyl)imide ([bmpy][Tf2N]), 1-(3,4,5,6-perfluorohexyl)-3-methylimdazolium bis(trifluoromethyl sulfonyl)imide ([perfluoro-hmim][Tf2N]), and 1-n-butyl-3-methylimidazolium tetrafluoroborate
([bmim][BF4]) are reported. A transient thin liquid film method was developed, which enables one to determine
the Henry's law constant and the diffusivity at low pressure simultaneously. Measurements were performed
at temperatures in the range of 283−323 K. Henry's law constants were in the range of 25.5−84 bar and
were in general agreement with measurements reported by other researchers for these and similar ionic liquids.
The entropies and enthalpies of absorption were determined to increase as gas solubility decreased. The
measured CO2 diffusion coefficients in the five ionic liquids were ∼10-6 cm2/s, which is an order of magnitude
smaller than the coefficients for CO2 diffusion in traditional organic solvents. In contrast to the gas solubility
results, measured diffusion coefficients were determined to be dependent on the ionic liquid cation as well as
the anion. In addition, CO2 diffusion coefficients were considerably more sensitive to temperature than were
CO2 solubilities in these ionic liquids. Results were used to develop a correlation relating CO2 diffusion to
ionic liquid properties and system temperature.