Selective Separation of Tocopherol Homologues by Liquid−Liquid Extraction Using Ionic Liquids

Abstract

Selective separation of tocopherol homologues was performed by liquid-liquid extraction, using ionic liquids (ILs) as extractants in the presence of diluent. The distribution coefficients and selectivities of tocopherols in the biphasic system were determined. A selectivity of δ-tocopherol to R-tocopherol up to 21.3 was achieved when using [bmim]Cl as extractant diluted by methanol. Considering the structural differences of tocopherols, the separation mechanism based on the hydrogen-bonding interaction between IL's anion and the -OH group on the tocopherols was proposed. The separation efficiency of IL was greatly affected by its anion, and followed the order [bmim]BF 4 < [bmim]CF 3 SO 3 < [bmim]Cl under the same conditions, which is consistent with the ascending order of IL's hydrogen-bond basicity strengths.

Ionic Liquid-Mediated Liquid-Liquid Extraction

“…As an alternative to the chromatographic methods, Yang et al carried out the liquid-liquid extraction of mixed tocopherol homologues with ILs (Yang et al, 2009). Since the four tocopherol homologues are likely to have different hydrogen bond acidities due to their structural difference in the number and position of methyl groups on the chromanol head, they may be effectively separated with each other by certain ILs via hydrogen bonding interaction.…”

“…Since the differences among the tocopherol homologues just lie in the different structural environment around the hydroxyl group, it appears that the selective separation probably results from the hydrogen bonding interaction between the hydroxyl groups and the chloride anion as expected. The methyl group which exists around the hydroxyl group of tocopherol could reduce tocopherol's hydrogen bond acidity and weaken the affinity of tocopherol for [C 4 (Yang et al, 2009). …”

“…Combined with the experimental results about tocopherol acetates, it was revealed that the hydrogen-bonding interaction between IL's anion and phenolic hydroxyl group played an important role on the separation selectivity. Reprinted from reference which is downloaded from pubs.acs.org (Yang et al, 2009 Table 3. Extractive separation of mixed tocopherols using different ILs at 303.15 K. Initial concentration of tocopherol in hexane (mg/ml): 0.54,&0.53, 0.11.…”

“…Mole ratio of IL to methanol: 1:1.3. Reprinted from reference which is downloaded from pubs.acs.org (Yang et al, 2009). …”

Process Analysis and Multi‐Objective Optimization of Ionic Liquid‐Containing Acetonitrile Process to Produce 1,3‐Butadiene

“…Currently, large amounts of literature are available on these topics, e.g., separating hydrocarbon mixtures [5][6][7][8][9], purifying biomacromolecules [10][11][12][13][14], scavenging liquid fuels [15][16][17][18][19][20][21], and extracting metal ions [22][23][24][25][26][27]. Although many advantages of ILs have been realized and many novel technologies have been developed on laboratory scale or pilot scale, the lack of knowledge on process assessments and predictive abilities for those new processes might cause potential failures in industrial applications.…”