应用分子模拟研究苯-噻吩二元体系的汽液相平衡

Research on the vapor-liquid equilibrium for benzene/thiophene binary system using molecular simulation

采用吉布斯系综蒙特卡洛(GEMC)方法和Tra PPE-UA力场,模拟了苯-噻吩二元体系在101.3 KPa下的汽液平衡性质,并通过一组对比模拟考察了噻吩点电荷对平衡组成的影响。两组模拟结果相近,均与实验值吻合良好,说明噻吩分子的点电荷可以被忽略,Tra PPE-UA力场可以准确预测简单二元芳香体系的汽液平衡性质。模拟得到的温度-组成相图比实验值宽,说明Tra PPE-UA力场对苯分子和噻吩分子间的相互作用力的预测偏低。此外,对径向分布函数的分析表明,苯-噻吩体系接近理想;组分间相对挥发度较小,并且随着体系温度的升高有增大的趋势,这符合我们在化学工程领域的常规认知。

Gibbs Ensemble Monte Carlo （GEMC） simulations using TraPPE-UA force field were performed to determine the phase diagram for the binary mixtures of benzene/thiophene at 101.3 KPa. Excellent agreement with experimental data was achieved, with unsigned errors of less than 6.5% and 8.49% for vapor and liquid equilibrium composition, respectively. Additional simulations were carried out to evaluate the influence of the partial charges on thiophene molecule and got similar results, indicating the charge assignment for thiophene is negligible in binary calculation; both T-x,y curves are somewhat wider than the experimental results because of the underestimation of the interactions between benzene and thiophene molecule. Generally, the transferability of TraPPE-UA force field to binary systems consisting of aromatic compounds was confirmed by all the simulations. Besides, the study on RDFs in the liquid phase shows that benzene/thiophene is an ideal mixture and the relative volatility between them is small, which is consistent with our previous understanding in chemical engineering.