Yang Yafan, Che Ruslan Mohd Fuad Anwari, Narayanan Nair Arun Kumar, Sun Shuyu
Physical Science and Engineering Division (PSE), Computational Transport Phenomena Laboratory , King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Saudi Arabia.
J Phys Chem B. 2019 Mar 28;123(12):2719-2727. doi: 10.1021/acs.jpcb.8b12033. Epub 2019 Mar 15.
Molecular dynamics simulations and theoretical analysis were carried out to study the bulk and interfacial properties of carbon dioxide-methane-water and carbon dioxide-methane-brine systems under geological conditions. The density gradient theory with the bulk phase properties estimated using the cubic-plus-association (CPA) equation of state (EoS) can well describe the increase in the interfacial tension (IFT) of the CO-water system in the presence of methane. The theoretical estimates of species mole fractions in the carbon dioxide-methane-water system are in good quantitative agreement with the experimental results. Furthermore, simulations of carbon dioxide-methane-brine system show that the IFT of the CaCl case is generally higher than that of the NaCl case. This is probably due to the stronger hydration of Ca ions and their stronger repulsion from the interface compared to Na. While the overall shape of the ionic profiles is not much affected by the ion type, the water profiles show a local enrichment at the interface in the system with CaCl. In contrast to the case of NaCl, the slopes of the plots of IFT vs CaCl concentration are dependent on temperature. Species mole fractions in the carbon dioxide-methane-brine system predicted by combining the CPA EoS with the Debye-Hückel electrostatic term are in good agreement with simulation results.
进行了分子动力学模拟和理论分析，以研究地质条件下二氧化碳 - 甲烷 - 水和二氧化碳 - 甲烷 - 盐水体系的体相和界面性质。使用立方加缔合（CPA）状态方程（EoS）估算体相性质的密度梯度理论能够很好地描述甲烷存在时CO - 水体系界面张力（IFT）的增加。二氧化碳 - 甲烷 - 水体系中各物种摩尔分数的理论估计值与实验结果在数量上吻合良好。此外，二氧化碳 - 甲烷 - 盐水体系的模拟表明，CaCl体系的IFT通常高于NaCl体系。这可能是由于Ca离子的水合作用更强，且与Na相比，它们与界面的排斥力更强。虽然离子分布的整体形状受离子类型影响不大，但在CaCl体系中，水分布在界面处呈现局部富集。与NaCl情况不同，IFT与CaCl浓度关系图的斜率取决于温度。将CPA EoS与德拜 - 休克尔静电项相结合预测的二氧化碳 - 甲烷 - 盐水体系中的物种摩尔分数与模拟结果吻合良好。
