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DETERMINATION OF HENRY'S LAW CONSTANTS FOR VOCS IN ROOM TEMPERATURE IONIC LIQUIDS
Citation:
SahleDemessie*, E, V Namboodiri**, J Enriquez*, U R. Pillai**, AND R S. Varma*. DETERMINATION OF HENRY'S LAW CONSTANTS FOR VOCS IN ROOM TEMPERATURE IONIC LIQUIDS. Presented at AIChE, San Francisco, CA, 11/16-21/2003.
Description:
Ionic liquids (ILs) have been shown to be a newer medium for a wide variety of chemical reactions and are considered as the potential replacements for traditional volatile organic solvents. However, the separation and recovery of organic compounds from ILs has not been systematically investigated. Partitioning of volatile organic compounds (VOCs) into room temperature ionic liquids affects the apparent vapor-liquid phase equilibrium of the VOCs in the medium. This partitioning can either complicate or facilitate the removal of VOCs from ionic liquids using standard separation processes. To predict and assess the performance of removing VOCs from ionic liquids, their partitioning from the IL and the headspace must be evaluated. While experimental solubility data of some of these VOCs in IL is available, there is only limited information on the vapor-liquid phase equilibrium of these systems at various temperatures.
In this study, the equilibrium partitioning in closed system (EPICS) headspace method was used to determine the partitioning of VOCs in IL over a wide range of temperatures. Headspace experiments were performed to quantify the effect of process variables, temperature (50 to 140EC) and concentration of VOC and type of ionic liquid on the Henry's law constants of VOCs. Partitioning of seven common VOCs in three ionic liquids, namely 1-butyl -3-methylimidazolium chloride [BMIM] [Cl], 1-Butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], 1-Butyl-3-methylimidazolium tetrafluroborate [BMIM][BF4], were determined. Henry's law constants were used to evaluate the potential of separating VOCs exploiting the inherent vapor pressure differences. The results of this study can be utilized to determine whether membrane based separation methods (pervaporation) can be used to isolate low boiling point compounds from ionic liquids. The ensuing thermodynamic data can form an important basis for designing processes to help remove un-reacted organic compounds (such as butyl chloride), in the preparative/purification of IL, to assist isolation of reaction products from IL, and could also be used in the dehydration of IL