Xu Wenhao, Yang Jichu, Hu Yinyu
Department of Chemical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.
J Phys Chem B. 2009 Apr 9;113(14):4781-9. doi: 10.1021/jp810193b.
Configurational-bias Monte Carlo simulations in the isobaric-isothermal ensemble using the TraPPE-UA force field were performed to study the microscopic structures and molecular interactions of mixtures containing supercritical carbon dioxide (scCO(2)) and ethanol (EtOH). The binary vapor-liquid coexisting curves were calculated at 298.17, 333.2, and 353.2 K and are in excellent agreement with experimental results. For the first time, three important interactions, i.e., EtOH-EtOH hydrogen bonding, EtOH-CO(2) hydrogen bonding, and EtOH-CO(2) electron donor-acceptor (EDA) bonding, in the mixtures were fully analyzed and compared. The EtOH mole fraction, temperature, and pressure effect on the three interactions was investigated and then explained by the competition of interactions between EtOH and CO(2) molecules. Analysis of the microscopic structures indicates a strong preference for the formation of EtOH-CO(2) hydrogen-bonded tetramers and pentamers at higher EtOH compositions. The distribution of aggregation sizes and types shows that a very large EtOH-EtOH hydrogen-bonded network exists in the mixtures, while only linear EtOH-CO(2) hydrogen-bonded and EDA-bonded dimers and trimers are present. Further analysis shows that EtOH-CO(2) EDA complex is more stable than the hydrogen-bonded one.
使用TraPPE-UA力场在等压等温系综中进行构型偏置蒙特卡罗模拟，以研究含有超临界二氧化碳（scCO₂）和乙醇（EtOH）的混合物的微观结构和分子间相互作用。计算了298.17、333.2和353.2 K下的二元气液共存曲线，其与实验结果高度吻合。首次对混合物中的三种重要相互作用，即乙醇-乙醇氢键、乙醇-二氧化碳氢键和乙醇-二氧化碳电子供体-受体（EDA）键进行了全面分析和比较。研究了乙醇摩尔分数、温度和压力对这三种相互作用的影响，并通过乙醇和二氧化碳分子间相互作用的竞争进行了解释。微观结构分析表明，在较高乙醇组成下，强烈倾向于形成乙醇-二氧化碳氢键连接的四聚体和五聚体。聚集体尺寸和类型的分布表明，混合物中存在非常大的乙醇-乙醇氢键网络，而仅存在线性的乙醇-二氧化碳氢键和EDA键连接的二聚体和三聚体。进一步分析表明，乙醇-二氧化碳EDA络合物比氢键络合物更稳定。
