Study On Extrction Of Unsaturated Fatty Acid Methyl Esters By Imidazolium Ionic Liquid

Due to the good chemical stability and thermal stability,imidazole-type ionic liquids have been used as a promising extractant in the extraction research field.The ionic liquid-supported liquid membrane technology combines the excellent solvent properties of ionic liquids with the advantages of high membrane separation efficiency to achieve highly efficient and continuous extraction.The focus of this dissertation is on the specific interaction between ionic liquids and unsaturated fatty acid methyl esters,and the excellent solvent properties of ionic liquids for the separation of unsaturated fatty acid methyl esters from fatty acid methyl ester mixtures.The main research contents and results are as follows:?1?It was found by IR characterization that the electron donors of the C=O and C=C could form hydrogen bonds with the H atoms on the imidazole ring of the ionic liquid.Therefore with the difference of C=C numbers,unsaturated fatty acid methyl ester could be selectively separated.?2?Imidazolium ionic liquids were used for the extraction of methyl linolenate.The effects of co-solvent and structure of anions and cations of ionic liquids on the separation were researched through extraction.Compared with pure solvents,organic solvent-ionic liquid extractants could increase the selectivity of unsaturated fatty acid methyl esters.In the aprotic solvent with low hydrogen-bonded basicity,the interaction between the ionic liquid and the fatty acid methyl ester was enhanced,which leads to an increasing selectivity.The increasing length of the alkyl substituent on the cation ring would improve the dissolution of fatty acid methyl ester in the extraction phase.The extraction selectivity of unsaturated fatty acid methyl esters increased gradually with lower hydrogen bond basicity of the anions.Using[EMIM][TF₂N]as extractant,acetonitrile as co-solvent,the selectivity would be:S_C18-3/C18-2=1.818,S_C18-3/C18-1=3.978,S_C18-3/C18-0=4.048??3?[C₄MIM][Cl]could increase the solubility of CuCl in acetonitrile.A better separation performance was obtained using CuCl-[C₄MIM][Cl]-acetonitrile than only using[C₄MIM][Cl]or CuCl with acetonitrile.For Acetonitrile-[C₄MIM][Cl]-CuCl,when the mole ratio of CuCl/[C₄MIM][Cl]was less than 1,increasing the Cu⁺concentration could effectively improve the selectivity.The highest selectivity was obtained when the concentration was 0.1 mol·L^-1.The selectivities of C18-3/C18-2,C18-3/C18-1 and C18-3/C18-0 were 1.77 and 3.16 and 33.56,respectively.AgBF₄could be well dissolved in the IL with anion[BF₄].The greater the Ag concentration,the greater selectivity could be obtained.When the concentration is 0.3g·mL-1,S_C18-3/C18-0 was 144.1-hexene was capable of stripping unsaturated fatty acid methyl esters from extractant than n-hexane,which could be applied in SILM.?4?An supported ionic liquid membrane?SILM?was prepared by coating the AgBF₄-[C₈Mim][BF₄]solution at the concentration of 2g·mL^-1 on the surface of a nylon membrane with pore size of 0.45um.The SILM was pretreated with 1-hexene,and was used to separate methyl linolenate.The mixture of 1-henxene and petroleum ether with the volume ratio of 1:9 was used as a stripping solvent.The purity of methyl linolenate was increased from 38.4%to 83.4%.The permeation flux of methyl linolenate was 0.3010 mg·?cm²·h?^-1.According to the mass transfer model,the permeation coefficients of the fatty acid methyl esters in the liquid membrane separation were calculated.When the pore size was 0.45um and the circulating rates of feedstock and stripping solvent were 79.2ml·min^-1,the permeability coefficient of C18-3,C18-2 and C18-1was 4.31×10^-99 m·s^-1,2.41×10^-9m·s^-1,and 2.73×10^-9m·s^-1respectively.