Wang Xiaoyu, Cheng Bingqing
Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria.
Department of Chemistry, University of California, Berkeley, California 94720, USA.
J Chem Phys. 2024 Jul 21;161(3). doi: 10.1063/5.0217232.
An azeotrope is a constant boiling point mixture, and its behavior is important for fluid separation processes. Predicting azeotropes from atomistic simulations is difficult due to the complexities and convergence problems of Monte Carlo and free-energy perturbation techniques. Here, we present a methodology for predicting the azeotropes of binary mixtures, which computes the compositional dependence of chemical potentials from molecular dynamics simulations using the S0 method and employs experimental boiling point and vaporization enthalpy data. Using this methodology, we reproduce the azeotropes, or lack thereof, in five case studies, including ethanol/water, ethanol/isooctane, methanol/water, hydrazine/water, and acetone/chloroform mixtures. We find that it is crucial to use the experimental boiling point and vaporization enthalpy for reliable azeotrope predictions, as empirical force fields are not accurate enough for these quantities. Finally, we use regular solution models to rationalize the azeotropes and reveal that they tend to form when the mixture components have similar boiling points and strong interactions.
共沸物是一种具有恒定沸点的混合物，其行为对于流体分离过程很重要。由于蒙特卡罗方法和自由能微扰技术的复杂性和收敛问题，从原子模拟预测共沸物具有挑战性。在此，我们提出了一种预测二元混合物共沸物的方法，该方法使用S0方法从分子动力学模拟计算化学势的组成依赖性，并采用实验沸点和汽化焓数据。使用这种方法，我们在包括乙醇/水、乙醇/异辛烷、甲醇/水、肼/水和丙酮/氯仿混合物在内的五个案例研究中重现了共沸物或不存在共沸物的情况。我们发现，对于可靠的共沸物预测，使用实验沸点和汽化焓至关重要，因为经验力场对于这些量不够准确。最后，我们使用正规溶液模型来解释共沸物，并揭示当混合物组分具有相似沸点和强相互作用时，它们倾向于形成。
