Sorption, Structure and Dynamics of CO2 and Ethane in Silicalite at High Pressure: A Combined Monte Carlo and Molecular Dynamics Simulation Study
Sorption, Structure and Dynamics of CO2 and Ethane in Silicalite at High Pressure: A Combined Monte Carlo and Molecular Dynamics Simulation Study
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DOI：
10.3390/molecules24010099
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发表时间：
2019-01-01
期刊：
影响因子：
4.6
通讯作者：
Cole, David
中科院分区：
文献类型：
--
作者：
Gautam, Siddharth;Liu, Tingting;Cole, David
硅质岩是一种重要的纳米多孔材料，在包括气体分离和催化在内的多个行业中有应用。虽然吸附，结构和动力学的几个分子限制在硅质岩的孔隙已经报道，这些研究大多数已被限制在低压。在这里，我们报告的吸附，结构和动力学的CO2和乙烷在硅质岩在高压（高达100巴）使用Monte Carlo（MC）和分子动力学（MD）模拟相结合的比较研究。这两种流体的行为进行了研究，在模拟的吸附等温线，吸附分子在硅质岩中的位置和取向分布，以及它们的平移扩散，振动光谱和旋转运动。发现CO2和乙烷在硅质岩孔隙中表现出取向有序;然而，在高压下，虽然CO2更喜欢驻留在通道交叉点，但乙烷分子主要驻留在正弦通道中。虽然CO2在低压下表现出比乙烷更高的自扩散系数，但在高压下，它变得比乙烷慢。CO2和乙烷在两个时间尺度上都表现出旋转运动。在这两个时间尺度上，乙烷的旋转运动更快。在这里观察到的CO2和乙烷在硅质岩孔隙中的行为的差异可以被看作是两个分子的动力学直径和CO2的四极矩的相互作用的结果。
Silicalite is an important nanoporous material that finds applications in several industries, including gas separation and catalysis. While the sorption, structure, and dynamics of several molecules confined in the pores of silicalite have been reported, most of these studies have been restricted to low pressures. Here we report a comparative study of sorption, structure, and dynamics of CO2 and ethane in silicalite at high pressures (up to 100 bar) using a combination of Monte Carlo (MC) and molecular dynamics (MD) simulations. The behavior of the two fluids is studied in terms of the simulated sorption isotherms, the positional and orientational distribution of sorbed molecules in silicalite, and their translational diffusion, vibrational spectra, and rotational motion. Both CO2 and ethane are found to exhibit orientational ordering in silicalite pores; however, at high pressures, while CO2 prefers to reside in the channel intersections, ethane molecules reside mostly in the sinusoidal channels. While CO2 exhibits a higher self-diffusion coefficient than ethane at low pressures, at high pressures, it becomes slower than ethane. Both CO2 and ethane exhibit rotational motion at two time scales. At both time scales, the rotational motion of ethane is faster. The differences observed here in the behavior of CO2 and ethane in silicalite pores can be seen as a consequence of an interplay of the kinetic diameter of the two molecules and the quadrupole moment of CO2.