| Compared with conventional organic solvents, ionic liquid (IL) has negligible vapor pressure, better thermal stability and chemical stability, and it can dissolve a large number of inorganic and organic compounds. There are a large number of ILs and different combinations of anions and cations can lead to the different functions. ILs are called "green solvents" and their functions can be designed, so they are regarded as potential solvents in the field of organic mixture separation. They can supplement conventional organic solvents or even replace them. Among so many separation techniques, liquid-liquid extraction has been applied widely. Compared with traditional solvents, ILs have better selectivities for separation. The data of infinite dilution activity coefficients y00 is very critical and useful for selecting solvents. Based on it, it’s available to calculate Hery constants, partition coefficients, infinite dilution selectivity factors and capacity factors, estimate mutual solubility, predict the existence of an azeotrope.This paper was mainly to investigate the distribution behaviors of a lot of organic compounds such as alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, aldehydes, esters, chloridemethanes and nitroparaffins in 1-butyl-2,3-dimethylimidazolium dicyanamide([bmmim][dca]) and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethyl-sulfonyl)imide, [bmmim][NTf2] at temperature 313.15 K,323.15 K and 333.15 K using gas chromatography. The static-wall-coated open-tubular (WCOT) columns with three different wall thicknesses were used to measure the retention time by gas chromatograph and the data of γ∞ was calculated by the revised equation. In addition, selectivity coefficients and capacity factors were calculated from the determined γ∞ values. γ∞ values of hydrocarbons with the same carbon number in [bmmim][dca] and [bmmim][NTf2] had the same order of alkanes> alkenes> cycloalkanes>(cycloalkenes)> alkynes>aromatics. Those of non-hydrocarbons with the same carbon number in [bmmim][dca] had the order of esters>aldehydes, nitroparaffin>ketones>alcohols, while those in [bmmim][NTf2] had the order of alcohols>ethers>esters, nitroparaffin>aldehydes>ketones. It indicated that there were strong intermolecular forces between alcohols and [dca]", which was due to the strong hydrogen bond between them. Similarly, n,π electron interactions between carbanyl group and S, O bond caused the strong intermolecular forces between aldehydes and [NTf2]-. The linear solvation energy relationship (LSER) model regression constants of [bmmim][dca] and [bmmim][NTf2] were obtained by linear fitting of partition coefficients. When C2H of imidazolyl was substituted by methyl, hydrogen-bond acidity would decrease and hydrogen-bond basicity would increase. At the same3 time, solubilities of ILs for organic compounds decreased. However, solubilities for different organic compounds decreased with the different range. It widened the solubility differences of partial organic systems. At last, the feasibility of [bmmim][dca] used as extractants for aromatics/alkanes, alkanes/alcohols and alkanes/alcohols mixtures and that of [bmmim][NTf2] for acetonitrile/cyclohexane, benzene/ethanol, acetone/hexane, toluene/methyl cyclohexane mixtures which were hard to separate had been investigated. The results showed that [bmmim][dca] and [bmmim][NTf2] had higher selectivities for those mixtures than convential solvents, and even for most of those mixtures than corresponding ILs with [bmim]+. It suggested that ILs with [bmmim]+ are potential extractants. |
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