Isobaric Vapor–Liquid Equilibrium of tert-Butyl Alcohol + Water + Triethanolamine-Based Ionic Liquid Ternary Systems at 101.3 kPa

Abstract

Isobaric vapor−liquid equilibrium (VLE) data for the tert-butyl alcohol (t-BuOH) + water + triethanolamine (TEA), t-BuOH + water + triethanolamine formic acid ([TEA][Fc]), t-BuOH + water + triethanolamine acetic acid ([TEA][Ac]), and t-BuOH + water + triethanolamine lactic acid ([TEA][Lc]) ternary systems were measured at 101.3 kPa. The results indicated that all the three ILs produced a more obvious effect on the VLE behavior of t-BuOH + water system than TEA, and eliminated the azeotropic point in the whole concentration range. [TEA][Lc] was the best solvent for the separation of the t-BuOH + water system by extractive distillation among the three ILs investigated. The experimental VLE data for the ternary systems were correlated with the NRTL model equation, and good correlations were obtained with an average relative deviation of 2.4 %. ■ INTRODUCTIONExtractive distillation is a widely used way to separate azeotropic or close-boiling mixtures like alcohol + water. 1,2 For this method, the key is to select an effictive solvent (entrainer) to break the azeotrope. Organic solvents and solid salts are commonly used entrainers, but encounter many problems in use such as solvent loss, difficulty in recycling, and equipment blocking. 3,4 Ionic liquids (ILs) are a new class of compounds that are entirely composed of ions. Because of their ignorable vapor pressure, good chemical and thermal stability, and other designable physical−chemical properties, ILs instead of traditional organic solvents and solid salts have been increasingly employed as entrainers for separating azeotropes in recent years. 5−14 tert-Butyl alcohol (t-BuOH) is an important solvent in the chemical and medicine industry. A mixture of t-BuOH and water is often used for the production of pharmaceutical products by freeze-drying. The t-BuOH + water mixture presents a minimum boiling azetrope at 353.06 K at atmospheric pressure. Thus, it is impossible to separate this mixture by simple distillation. Extractive distillation is widely adopted to separate this mixture. The traditional solvent (entrainer) is ethylene glycol, which suffers the disadvantages of solvent loss and poor efficiency. ILs have been employed as new solvents to separate this azetrope in recent years. Most of the studies were performed using 1-alkyl-3-methylimidazolium based ILs, the anions of which are carboxylate or halide. Zhang et al. 15 studied the relative volatility of t-BuOH to water effected by the ILs composed of an anion chosen from [OAc] − or [Cl] − , and a cation from 1-ethyl-3-methylimidazolium ([EMIM] + ), or 1-butyl-3-methylimidazolium ([BMIM] + ), or 1-hexyl-3-methylimidazolium ([HMIM] + ), at a fixed t-BuOH mole fraction of 0.95. The effect of ILs on enhancement of the relative volatility list as [EMIM]Cl > [EMIM]OAc > [BMIM]Cl > [BMIM]OAc > [HMIM]OAc > [HMIM]Cl. These ILs were also used as entrainers to separate the methyl alcohol + water and ethyl alcohol + water azeotropic systems. 16−18 However, there is a paucity of studies on other kinds of ILs, so it is neces...

Isobaric vapor–liquid equilibrium of tert‐butanol + water + ionic liquids at atmospheric pressure

“…Experimental data The binary VLE experimental data for TBA (1) + water (2) were obtained at atmospheric pressure and the results are shown in Table 3. The experimental results were in good agreement with data from the literature 23,26,27 and the results are compared in Fig. 1.…”

“…Isobaric y 1 – x 1 data for TBA (1) + water (2) at 101.3 kPa: , experimental data; , from Ref. 23; , from Ref. 26; , from Ref.…”

“…12. Moreover, α 12 with the addition of the two phosphate‐based ILs ([MMIM][DMP] or [EMIM][DEP]) is compared with that with the addition of other ILs or mixed solvents 23, 24, 26‐28 in Fig. 12.…”

“…For the binary azeotrope of TBA and water, ILs used as the solvent to separate them have been introduced. The ILs triethanolamine lactic acid ([TEA][Lc]), triethanolamine acetic acid and triethanolamine formic acid were used by Zhang et al 23 . and the results showed that the separating efficiency of [TEA][Lc] was the best.…”

“…For the binary azeotrope of TBA and water, ILs used as the solvent to separate them have been introduced. The ILs triethanolamine lactic acid ([TEA] [Lc]), triethanolamine acetic acid and triethanolamine formic acid were used by Zhang et al 23 and the results showed that the separating efficiency of [TEA][Lc] was the best. The ILs 1-hexyl-3-methylimidazolium bromine, 1-butyl-3-methylimidazolium bromine and 1-ethyl-3-methylimidazolium bromine ([EMIM][Br]) were used by Zhang et al 24 28 and the results indicated that the azeotropic point could be destroyed after using the mixed solvent in various ratios.…”