Study On The Physico-chemical Properties Of Propionate Ionic Liquids And Its Aqueous Solutions

As a "new generation" green and environment-friendly solvent, carboxylic acidionic liquids has attractted more and more attentions and researches, and arespecialized by green, non-toxic, non-polluting and can be designed. In this paper weuse propionic acid ionic liquid as the object of study, using its thermodynamicproperties of the physicochemical properties as the main body of the study, thefollowing work has done:Using the neutralizational process, the syntheses of five propionate ionic liquids（PrAILs）[C_nmim][Pro]（n=2,3,4,5,6）,1-ethyl-3-methylimidazoliumpropionate （[C₂mim][Pro]）,1-propyl-3-methylimidazolium propionate（[C₃mim][Pro]）,1-butyl-3-methylimidazolium propionate （[C₄mim][Pro]）,1-pentyl-3-methylimidazole propionate （[C₅mim][Pro]） and1-hexyl-3-methylimidazoliumpropionate （[C6mim][Pro]）, using1H NMR and differential scanning calorimetry（DSC） and other modern analytical instruments, they were characterized.Using the standard addition method （SAM）, with different water content, wemeasured the experimental values of the surface tension, density and refractiveindex of the ionic liquids in the temperature range of288.15K-338.15K, and inaccordance with the linear fit, within the same temperature range, the surface tension,density and refractive index of PrAILs excluding water can be obtained, and itsresearch are applied, and the estimate values obtained correspond quiet well withthe experimental values.According to the Glasser theory, using the experimental value of the density ofthe propionic acid ionic liquids （PrAILs）, we estimated the lattice energy andstandard entropy of the PrAILs. Meanwhile, according to the experimental values ofthe refractive index of the PrAILs, we calculated the molar polarization andpolarization rate of the PrAILs, respectively.Using the experimental values of the surface tension of the PrAILs we calculatedand obtained the parachor values, we obtained the parachor values of [C_nmim]+usingthe Extrathermodynamic assumption, and thus we get a conclusion: the parachor values of the anions of [Cnmim][Pro],[C₂mim][RBF₃](R=N-C_nH_2n+1（n=1–5）),[C_nmim][Gly],[Cnmim][PF₃（CF₂CF₃）₃].Since the purity of ionic liquids have a great impact on the properties of theirchemical compounds, we measured the density and surface tension of the solution ofionic liquids of PrAILs in the concentration range of0.0400～0.5000mol·kg-1and inthe temperature range of288.15K-338.15K, and obtained the experimental values ofthe parachor of the solutions. We also used the empirical formula of the parachor andthe surface tension model for the solution proposed by Yigui Li et.al,for determiningthe surface tension of the aqueous solution of ionic liquids, respectively, and theestimated values are in good agreement with the experimental values, we also usedthe empirical formula of the parachor to the research of the surface tension of theaqueous solution of ionic liquids at298.15K,and it turned out to be quite reasonable.These estimate values, is very important in the in-depth researches of the ionicliquids.