Volumetric Property Prediction for Ionic Liquids using COSMO-RS
Sustainable process-product development & green chemistry
Modelling, Design & Analysis of Processes with Ionic Liquids (T1-1P)
Keywords: ionic liquids, volumetric properties, COSMO-RS
Jose Palomar,*1 Victor R. Ferro,1 J. Torrecilla2
1 Sección de Ingeniería Química (Dpt. Química Física Aplicada), Universidad Autónoma de Madrid,Cantoblanco, 28049 Madrid, Spain. 1 Departamento de Ingeniería Química, Universidad Complutense de Madrid, 28040 Madrid, Spain.
The specific density and molar liquid volume of forty imidazolium based ionic liquids were predicted using COSMO-RS model, a thermodynamic model based on quantum chemistry calculations. A molecular model of ion-pairs was proposed to simulate the pure ionic liquid compounds. These ion-paired structures were generated at B3LYP/6-31++G** by combining the cations 1-methyl- (Mmim+), 1-ethyl- (Emim+), 1-butyl- (Bmim+), 1-hexyl- (Hxmim+) and 1-octyl-3-methylimidazolium (Omim+) with the anions chloride (Cl-), tetrafluoroborate (BF4-), tetrachloroferrate (FeCl4-), hexafluorophosphate (PF6-), bis(trifluoromethanesulfonyl)imide (TfN-), methylsulfate (MSO4-), ethylsulfate (EtSO4-) and trifluoromethanesulfonate (CF3SO3-), using the quantum chemical software Gaussian03. Excellent agreement with the available experimental measurements was obtained, showing the capability of current computational approach to describe the effect of the anion nature and cation substituent on the volumetric properties of this family of ionic liquids. Thus, calculated and experimental density values of ionic liquids (and also other common solvents) were fitted by linear regressions with correlation coefficients R > 0.99 and standard deviations SD < 20 kg/m3. Consequently, molar liquid volumes were also predicted very accurately, despite the scarce experimental available data. The good predictions of COSMO-RS indicated the suitability of the ion-pair model to describe intermolecular interactions of pure ionic liquids. In addition, the σ-profiles of the ion-paired molecules were used to qualitatively interpret the intermolecular interactions in ionic liquids which influences on their volumetric properties. Furthermore, we show that the surface area below the σ-profile (Sσ-profile) may be used as a unique a-priori parameter to characterize the contribution of cation and anion to the ionic liquid behavior in design solvent tools.
Presented Monday 17, 13:30 to 15:00, in session Modelling, Design & Analysis of Processes with Ionic Liquids (T1-1P).
