A novel application of supported liquid membranes based on ionic liquids to the selective simultaneous separation of the substrates and products of a transesterification reaction

This work evaluates the use of ionic liquids (ILs) based on 1-n-alkyl-3-methylimidazolium cation (n-butyl, n-octyl) and the hexafluorophosphate anion, as liquid phase in supported liquid membranes (SLMs) for the selective separation of vinyl butyrate, 1-butanol, butyl butyrate and butyric acid, which are substrates and products of a transesterification reaction. No significant permeability differences was observed between the permeabilities of the compounds when five polymeric membranes (Fluoropore, Durapore, Mitex, Isopore and Nylon) were used. However, transport selectivity was dramatically increased when the same membranes were used with [bmim+][PF6−] immobilized, especially in the case of membranes of a hydrophilic nature (Nylon and Isopore). Good permeabilities and selectivities were also found when [omim+][PF6−] was immobilized in the Nylon membrane. The molecular mechanism involved in the transport phenomena through the SLMs has been also investigated by determining the partition coefficients of the different compounds between hexane and the ILs, concluding that transport is mainly regulated by the ionic liquidʹs affinity towards each solute. As regards the operational stability of these SLMs, they were seen to be remarkably stable when tested over eight continuous cycles of 48 h each.