A volumetric and intra-diffusion study of solutions of AlCl<sub>3</sub> in two ionic liquids - [C<sub>2</sub>TMEDA][Tf<sub>2</sub>N] and [C<sub>4</sub>mpyr][Tf<sub>2</sub>N]
A volumetric and intra-diffusion study of solutions of AlCl<sub>3</sub> in two ionic liquids - [C<sub>2</sub>TMEDA][Tf<sub>2</sub>N] and [C<sub>4</sub>mpyr][Tf<sub>2</sub>N]
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AlCl<sub>3</sub> 在两种离子液体 - [C<sub>2</sub>TMEDA][Tf<sub>2</sub>N] 和 [
DOI：
10.1039/d2cp03304f
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发表时间：
2022
影响因子：
3.3
通讯作者：
Ruther Thomas
中科院分区：
文献类型：
--
作者：
Harris Kenneth R.;Kanai Noriko;Price William S.;Torres Allan M.;Willis Scott A.;Rodopoulos Theo;Veder Jean-Pierre;Ruther Thomas
测量了离子液体1-(2-dimethyl-aminoethyl)-dimethylethylammonium双(三氟甲基磺酰)酰胺([C2TMEDA][Tf2N])和N-丁基-N-甲基吡咯烷胺([C4mpyr][Tf2N])在三氯化铝(AlCl3)溶液中的内扩散系数，以考察光谱检测到的离子与AlCl3之间的相互作用是否影响这些性质。这种电解液对铝的电积很有意义。研究了温度、组成和摩尔体积的关系。根据溶液密度计算了AlCl3的表观体积(Vϕ，1)和偏摩尔体积(V1)。对于[C2TMEDA][Tf2N]溶液，Vϕ，1随着溶质浓度的增加而增大；对于[C4mpyr][Tf2N]溶液，则减小。在纯[C2TMEDA][Tf2N]中，阳离子的扩散速度比阴离子快，但随着AlCl3浓度的增加而变化。在[C4mpyr][Tf2N]溶液中，内扩散系数比与纯离子液体的内扩散系数之比相同，铝物种在每种组成下的扩散速度与阴离子的扩散速度大致相同。通过将等浓度曲线与浓度相关但与温度无关的摩尔体积偏移量叠加，内扩散系数可符合Ertl-Dullien自由体积幂定律。这表明它们主要依赖于摩尔体积，其次是由于AlCl3的稀释而产生的综合热力学因素。~(27)Al、~(15)N和~(19)F核磁共振谱证实，[Tf_2N]−和[C_2TMEDA]+与AlCl3的络合作用较小。我们的结果表明，自由体积理论在研究离子液体溶液和混合物的输运性质方面可能是卓有成效的。
Intra-diffusion coefficients (DSi) have been measured for the ionic liquid constituent ions and aluminium-containing species in aluminium chloride (AlCl3) solutions in the ionic liquids 1-(2-dimethyl-aminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide ([C2TMEDA][Tf2N]) and N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][Tf2N]), to investigate whether spectroscopically detected interactions between the ions and AlCl3 affect these properties. Such electrolyte solutions are of interest for the electrowinning of aluminium. The temperature, composition and molar volume dependences are investigated. Apparent (Vϕ,1) and partial molar (V1) volumes for AlCl3 have been calculated from solution densities. For [C2TMEDA][Tf2N] solutions, Vϕ,1 increases with increasing solute concentration; for [C4mpyr][Tf2N] solutions, it decreases. In pure [C2TMEDA][Tf2N], the cation diffuses more quickly than the anion, but this changes as the AlCl3 concentration increases. In the [C4mpyr][Tf2N] solutions, the intra-diffusion coefficient ratio remains equal to that for the pure ionic liquid and the aluminium species diffuses at approximately the same rate as the anion at each composition. The intra-diffusion coefficients can be fitted to the Ertl–Dullien free volume power law by superposing the iso-concentration curves with concentration dependent, but temperature independent, molar volume offsets. This suggests that they are primarily dependent on the molar volume and secondarily on a colligative thermodynamic factor due to dilution by AlCl3. AlCl3 complexation by [Tf2N]− and [C2TMEDA]+, confirmed by 27Al, 15N and 19F NMR spectroscopy, seems to play a minor role. Our results indicate that the application of free volume theories might be fruitful in the study of the transport properties of ionic liquid solutions and mixtures.