Molecular Simulation of Transport Across An Alcohol/Ionic Liquid Interface

The interfacial properties of ionic liquids (IL) and organic phases are important factors that may dominate mass transport of IL biphasic reactions. In this molecular dynamic (MD) simulation, we constructed an interface between BF₄ type ionic liquid, e.g., 1-butyl-3-methylimidazolium tetrafluoroborate, and a coexisting alcohol (pentanol), one of the main products of hydroformylation reaction. This IL/alcohol choice is based on our published laboratory results. For the initial configuration, an extra ion-pair/cluster (ball-style molecules in the figure) is placed in the alcohol phase and close to the interface. The kinetics of ion-clusters transfer between IL (blue and green, bond style) and n-pentanol (line style) phases were investigated. Several molecular-scale events of ion-cluster motion are analyzed, which include (i) attachment to the ionic-liquid surface, (ii) interfacial dissociation, and (iii) diffusion and dispersal into bulk IL environments. From such molecular-scale events the relative solubility of an ion pair in the pentanol phase is obtained. Finally, MD simulation on smaller alcohols - which our lab experiments have shown to solubilize this IL much faster - will be compared to those on pentanol.