The development of ionic liquids (ILs) with strong hydrogen-bond basicity is of great importance for the application of ILs in liquid–liquid extractions, but a long-standing problem is that the increase in hydrogen-bond basicity of ILs usually comes along with undesired changes in other properties such as reduced lipophilicity, raised melting point, and difficulty of forming biphasic systems with water. Herein, we provided a promising solution to this problem by synthesizing a class of functional phosphonium ILs with the use of biocompatible saturated/unsaturated long-chain fatty acids (carbon number up to 20) as anion precursors, and we also carried out systematic investigations on their physicochemical properties. These long-chain fatty acid ILs (LCFA-ILs) featured very strong hydrogen-bond basicity, up to the top level of all reported solvents, along with good lipophilicity and a wide liquid range. Moreover, the viscosity of LCFA-ILs exhibited only a slight increase with increasing chain length, and the hydrophilicity/hydrophobicity could be tuned by a change in the side chain of the phosphonium cation. Excellent extraction efficiency was achieved by applying LCFA-ILs to both aqueous and nonaqueous extractions. The distribution coefficients of specific solutes reached unprecedented values up to 3000–5000, which were 17–650 times higher than those by common ILs and molecular solvents.
The separation of 1,3-butadiene (1,3-C4H6) and n-butene (n-C4H8) using ionic liquids (ILs) has received great attention in recent years, but designing an industrially attractive IL that combines large solubility and high selectivity remains challenging. In this work, we prepared several tributylethylphosphonium-based carboxylate ILs featuring large free volume and strong hydrogen bonding basicities through finely tuning the structures of cations and anions for the separation of C4 hydrocarbons. These carboxylate ILs exhibited the highest mass solubility for 1,3-C4H6 yet reported (0.899 and 0.663 mmol/g in [P4442][C17H35COO] and [P4442][HCOO], respectively) and excellent 1,3-C4H6/n-C4H8 selectivity (1.83 in [P4442][HCOO]) at 308.1 K and 100 kPa, which sets a new benchmark for 1,3-C4H6/n-C4H8 separation. Qualitative relationships between the free volume/basicity and their solubility were established. Results revealed that the free volume of unit mass and basicity were positively correlated with the 1,3-C4H6 solubility. The interaction between the ILs and gases was explored by quantum chemical calculations.
Han Yue,Yuxiang Liu,Yidong Gu,Xiwei Hu,Jiaming Zhu,Qunsheng Li
The solubility of trans-3-hydroxycinnamic acid in pure solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, and n-propyl acetate) and (ethanol + ethyl acetate) cosolvent mixtures was measured by the gravimetric method from 293.15 to 333.15 K in normal pressure. The experimental results show that the solubility of 3-HCA(E) in alcohol solvents is greater than in ester solvents, which conforms to “like dissolves like”. On this basis, the experimental result was correlated with semiempirical models (the modified Apelblat, van’t Hoff, λh, Jouyban–Acree–van’t Hoff equation, and combined model) and activity coefficient models (Wilson, NRTL, and UNIQUAC equation). The modified Apelblat model has the best correlation of the experimental data, with an ARD of less than 0.5% for pure solvents and cosolvent mixtures. The solvent effect was calculated by the KAT-LSER equation, showing that the hydrogen bond alkalinity of solvents–solutes (β) and the solvent self-association (δH) significantly influence the solubility of 3-HCA(E), accounting for 32.46 and 55.02%, respectively. Finally, the thermodynamic parameters (ΔHmix, ΔSmix, ΔGmix,%ξH, and %ξTS) were calculated. Negative values of both ΔHmix and ΔGmix indicate that the mixing process of 3-HCA(E) is exothermic and spontaneous. The Gibbs energy of the mixing process is jointly contributed by enthalpy and entropy.
危险品化学品经营许可证（带存储）