水–甲硫醇–二甲硫醚三元体系的气液平衡模拟

Simulation of Vapor-Liquid Equilibrium for the Water-Methyl Mercaptan-Dimethyl Sulfide Ternary System

摘要: 本文聚焦于水–甲硫醇–二甲硫醚三元体系的气液平衡开展模拟研究。鉴于该体系存在三元共沸特性，致使在甲硫醇钠生产进程中，塔顶难以获取合格的甲硫醇产品，从而对下游二甲基亚砜产品的纯度产生负面影响。为妥善解决此问题，本研究借助Material Studio和Gaussian 09W软件，构建了水、甲硫醇以及二甲硫醚的分子模型，并对其进行结构优化，同时完成COSMO文件的计算。通过运用COSMO-RS方法，对该三元体系在不同温度条件下的相互作用力以及超额焓的变化态势予以预测。研究结果表明，在不同温度区间，体系的超额焓呈现出显著差异，且范德华力在超额焓的贡献中占据主导地位。此外，本文运用Aspen软件针对该体系的二元相图展开模拟分析，结果显示NRTL方程对该体系具备良好的模拟效果。本研究成果为该体系的分离回收提供了坚实的理论支撑，有助于提升二甲基亚砜的纯度，进而有力推动其在电子等新兴市场领域的广泛应用。

Abstract: This paper investigates the vapor-liquid equilibrium (VLE) of the water-methyl mercaptan (MME)-dimethyl sulfide (DMS) ternary system through simulation. The presence of an azeotrope in this system leads to the inability to obtain pure methyl mercaptan at the top of the distillation column during the production of methyl mercaptan sodium, which in turn affects the purity of downstream dimethyl sulfoxide (DMSO) products. To address this issue, molecular models of water, MME, and DMS were established using Material Studio and Gaussian 09W software. The structures were optimized, and COSMO files were generated. The COSMO-RS method was employed to predict the interactions and excess enthalpy of the ternary system at different temperatures. The results showed that the excess enthalpy of the system varies with temperature, and van der Waals forces are the primary contributors to the excess enthalpy, followed by electrostatic and hydrogen bonding forces. Additionally, Aspen software was used to simulate the binary phase diagrams of the system, revealing that the NRTL equation provides good simulation results for this system. This study provides a theoretical basis for the separation and recovery of the system, which is beneficial for improving the purity of DMSO and promoting its application in emerging markets such as electronics.