Feria Esther, Algaba Jesús, Míguez José Manuel, Mejía Andrés, Gómez-Álvarez Paula, Blas Felipe J
Laboratorio de Simulación Molecular y Química Computacional, CIQSO-Centro de Investigación en Química Sostenible and Departamento de Ciencias Integradas, Universidad de Huelva, 21007 Huelva, Spain.
Phys Chem Chem Phys. 2020 Mar 7;22(9):4974-4983. doi: 10.1039/c9cp06397h. Epub 2020 Feb 21.
We have determined the phase equilibria and interfacial properties of a methyl ester homologous series (from methyl acetate to methyl heptanoate) using direct simulations of the vapour-liquid interfaces. The methyl esters are modelled using the united atom approach in combination with transferable parameters for phase equilibria (TraPPE) force fields for alkanes, alkenes, carbon dioxide, ethers, and carboxylic acids in a transferable way. This allows us to take into account explicitly both dispersive and coulombic interactions, as well as the repulsive Pauli-exclusion interactions. Simulations are performed in the NVT or canonical ensemble using molecular dynamics. Vapour-liquid surface tension is determined using the virial route, i.e., evaluating the normal and tangential components of the pressure tensor along the simulation box. We have also calculated density profiles, coexistence densities, vapour pressures, surface entropies and enthalpies, and interfacial thickness as functions of temperature, as well as the normal boiling temperatures and the critical temperatures, densities, and pressures for each member of the series. Special attention is paid to the comparison between experimental data taken from the literature and our results obtained using molecular dynamics simulations. We also analyze the effect of increasing the molecular weight of the methyl esters (at fixed temperature) on all the properties considered, with special emphasis on phase equilibria envelopes and surface tension. The TraPPE force fields transferred from other molecules and chemical families are able to predict very accurately the experimental vapour-liquid phase envelopes of methyl esters. We also compare the results obtained from simulations of the surface tension, with experimental data taken from the literature. To our knowledge, this is the first time that vapour-liquid phase equilibria and interfacial properties, and particularly surface tension, of this methyl ester homologous series are obtained using computer simulation.
我们通过对气液界面进行直接模拟，确定了一个甲酯同系物系列（从乙酸甲酯到庚酸甲酯）的相平衡和界面性质。甲酯采用联合原子方法建模，并结合了可转移的相平衡参数（TraPPE）力场，该力场可用于烷烃、烯烃、二氧化碳、醚和羧酸，且具有可转移性。这使我们能够明确考虑色散相互作用和库仑相互作用，以及排斥性的泡利不相容相互作用。使用分子动力学在NVT或正则系综中进行模拟。气液表面张力通过维里途径确定，即沿着模拟盒评估压力张量的法向和切向分量。我们还计算了密度分布、共存密度、蒸气压、表面熵和焓、界面厚度随温度的变化函数，以及该系列每个成员的正常沸点温度和临界温度、密度和压力。特别关注将文献中的实验数据与我们使用分子动力学模拟获得的结果进行比较。我们还分析了在固定温度下增加甲酯分子量对所有考虑性质的影响，特别强调相平衡包络和表面张力。从其他分子和化学家族转移而来的TraPPE力场能够非常准确地预测甲酯的实验气液相平衡包络。我们还将表面张力模拟结果与文献中的实验数据进行了比较。据我们所知，这是首次使用计算机模拟获得该甲酯同系物系列的气液相平衡和界面性质，特别是表面张力。
