Elsevier

Fluid Phase Equilibria

Volume 251, Issue 1, 15 January 2007, Pages 68-70
Fluid Phase Equilibria

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Study on solid–liquid phase equilibria in ionic liquid: 1. The solubility of alkali chloride (MCl) in ionic liquid EMISE

https://doi.org/10.1016/j.fluid.2006.10.018Get rights and content

Abstract

This paper reports the solubility of alkali chloride MCl (M is Li, Na and K) in IL EMISE was measured in the temperature range of 293.15 K to 343.15 K. The relationship between solubility, m and temperature T may be expressed in an empiric formula: ln(m/m0) = A1 + A2T0/T + A3T/T0, where m0 is 1 mol/kg, T0 is 1 K. The observed sequence of solubility is LiCl > NaCl > KCl. The fact implies that the less the radius of alkali ion, the greater is its solubility because little ion is easy to get into the interstices of IL EMISE.

Introduction

Ionic liquids (ILs) are viewed as a novel class of green benign solvents, which promise widespread application in industry, possibly replacing currently used organic solvents due to unique properties such as negligible vapor pressures, broad liquid temperature ranges, and high specific solvent abilities, etc. The haloaluminate(III) ionic liquids, initially developed in the late 1940s by Hurley and Wier [1], have found infrequent use as solvent systems due to their moisture and air-sensitivity. The report in 1992 by Wilkes and Zaworotko [2] of air- and moisture-stable ionic liquids opened the door for their application in conventional chemical reactions. Since then many new air- and water-stable ILs were increasingly reported [3], [4], [5], [6]. Despite the fundamental physical–chemical properties of this class ILs have been extensively studied, there are very few reports of solubility of inorganic salts in ILs. Since solubility of metal ions in ILs are extremely important to the applications of ILs in synthesis and extraction, as a continuation of our previous investigation [7], [8], [9], [10], [11]. This paper reports the solubility of alkali chloride MCl (M is Li, Na and K) in IL EMISE was measured in the temperature range of 293.15 K to 343.15 K. The relationship between solubility, m and temperature T may be expressed in an empiric formula: ln(m/m0) = A1 + A2T0/T + A3T/T0, where m0 is 1 mol/kg, T0 is 1 K. At the same time, the observed sequence of solubility is LiCl > NaCl > KCl. The fact implies that the less the radius of alkali ion, the greater is its solubility because little ion is easy to get into the interstice of IL EMISE.

Section snippets

Chemicals

Diethyl sulfate was used as supplied. Toluene was AR reagent and was purified by standard method. 1-Methylimidazole (AR reagent) was distilled under reduced pressure. KCl and NaCl with purity more than 99.99% was dried in a vacuum oven at 408 K for 6 h. LiCl (AR reagent from Tianjin chemistry reagent factory) was recrystallized from water and dried at 400 °C before use.

Synthesis of 1-ethyl-3-methylimidazolium ethyl sulfate

1-Ethyl-3-methylimidazolium ethyl sulfate is a new ionic liquid which is prepared by alkylation of 1-methylimidazole with diethyl

Results and discussion

The values of the solubility of LiCl, KCl and NaCl in EMISE at 293.15–343.15 K are listed in Table 1. Each value in Table 1 is the average of three determinations.

The polarity of liquid is an important quantity while a solvent was selected for application. As is known to all, ionic liquid only composes of cation and anion and was regarded as solvent of strong polarity. According to general rule, the salt would easy dissolve in the ionic liquid with strong polarity. However, in our experiments,

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