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Adsorption and Phase Behavior of Pure/Mixed Alkanes in Nanoslit Graphite Pores: An iSAFT Application
Langmuir ( IF 3.9 ) Pub Date : 2017-09-12 00:00:00 , DOI: 10.1021/acs.langmuir.7b02055
Jinlu Liu 1 , Le Wang 1 , Shun Xi 1 , Dilip Asthagiri 1 , Walter G. Chapman 1
Affiliation  

The prediction of fluid phase behavior in nanoscale pores is critical for shale gas/oil development. In this work, we use a molecular density functional theory (DFT) to study the effect of molecular size and shape on partitioning to graphite nanopores as a model of shale. Here, interfacial statistical associating fluid theory (iSAFT) is applied to model alkane (C1 – C8) adsorption/desorption/phase behavior in graphite slit pores for both pure fluids and mixtures. The pure component parameters were fit to the bulk saturated liquid density and vapor pressure data in selected temperature ranges. The potential of interaction between the fluid and graphite is modeled with a Steele 10-4-3 potential that is fit to the potential of mean force from single-molecule simulations. Good agreement is found between theory and molecular simulation for the density distributions of pure components in slit pores. The critical properties of methane, ethane, and their mixtures as well as the shift in bubble point and dew point densities were studied, showing good agreement with simulation. The competitive adsorption of mixtures of normal and branched alkanes in graphite pores was also studied. Heavier components more strongly adsorb up to the point that the entropic penalty due to confinement reduces adsorption.

中文翻译:

纯/混合烷烃在纳米狭缝石墨孔中的吸附和相行为:iSAFT应用

预测纳米级孔隙中的液相行为对于页岩气/油开发至关重要。在这项工作中,我们使用分子密度泛函理论(DFT)来研究分子大小和形状对页岩模型向石墨纳米孔分配的影响。在这里,界面统计缔合流体理论(iSAFT)被应用于烷烃模型(C 1 – C 8)纯流体和混合物在石墨狭缝孔中的吸附/解吸/相行为。在选定的温度范围内,纯组分参数适合于总体饱和液体密度和蒸气压数据。流体和石墨之间相互作用的电势用Steele 10-4-3电势建模,该电势适合于单分子模拟的平均力电势。在理论和分子模拟之间发现缝隙孔中纯组分的密度分布有很好的一致性。研究了甲烷,乙烷及其混合物的临界性质,以及沸点和露点密度的变化,与模拟结果吻合良好。还研究了正构烷烃和支链烷烃混合物在石墨孔中的竞争性吸附。
更新日期:2017-09-12
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