咪唑醋酸离子液体热力学性质的理论研究

A Theoretical Study of the Thermodynamic Properties of Imidazolium Acetate Ionic Liquids

咪唑醋酸离子液体在催化、电化学、萃取等领域具有潜在的应用价值,对其热力学性质的深入研究将为其应用提供理论依据。本文采用密度泛函理论(DFT)方法和Born-Fajans-Haber(BFH)循环法对咪唑醋酸离子液体[C_nmim][OAc](n=1-6)进行热力学性质的理论研究。计算其相变过程中的解离焓、汽化焓、熔化焓、晶格焓、溶解焓等,并与已有实验值进行比较。利用Gaussian 09程序在B3LYP/6-311+G(d,p)和M062X/TZVP两种水平下计算解离焓值,同时通过计算得到分子体积和总气相能的焓修正值,借助Matlab计算软件拟合得到汽化焓值,取得与已有实验值很好的一致性。使用Jenkins公式求得晶格能,计算得到晶格焓,最后利用BFH循环计算得到溶解焓。

Imidazolium acetate ionic liquids have a wide range of applications in catalysis, electrochemistry and extraction, and an improved understanding of their thermodynamic properties will provide a theoretical basis for future usages in related fields. In this work, density functional theory （DFT） and the Born-Fajans-Haber （BFH） cycle were used to study the thermodynamic properties of imidazolium acetate ionic liquids [Cnmim][OAc] （n = 1- 6）. The dissociation, vaporization, latticeand solvation phase transition enthalpies of these liquids were calculated and compared with the corresponding experimental values. The dissociation enthalpies were determined using DFT at the B3LYP/6-311 ＋G（d, p） and M062X/TZVP levels, and the results were compared with literature values. In addition, enthalpy of vaporization values were obtained from molecular volumesin conjunction with enthalpic corrections to the total gas-phase energy and Matlab fitting parameters, and the results were in good agreement with experimental data. Lastly, using the Jenkins formula, the lattice energies and the corresponding lattice enthalpies were determined, while the solvation enthalpies were calculated by employing the BFH cycle.