Journal
CHEMICAL ENGINEERING JOURNAL
Volume 420, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.127578
Keywords
Adsorption thickness; Structural morphology; Liquid hydrocarbon; Nanoscale; Shale oil; Molecular dynamics
Categories
Funding
- National Postdoctoral Program for Innovative Talents [BX201700287]
- National Natural Science Foundation of China [41802151, 41972163]
- China Postdoctoral Science Foundation [2018M641597]
- Science Foundation of China University of Petroleum, Beijing [2462017YJRC031]
- Sinopec Science and Technology Program [P200573]
- UAEU [G00003530]
- National Science and Technology Special Grant [2016ZX05006001, 2016ZX05033]
- PetroChina Innovation Foundation [2018D50070102]
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Adsorption of liquid hydrocarbons in clay minerals was studied through molecular dynamics simulations, showing different adsorption capacities based on hydrocarbon type and structural morphology. The adsorption behavior is influenced by the pore size of the adsorbent and the polarity of the hydrocarbon component, affecting the interaction between hydrocarbon and clay minerals.
As adsorption can influence the phase behavior of shale oils, and consequently their transport, understanding the adsorption behavior of liquid hydrocarbons in shale is essential for the utilization of this valuable resource. In this work, the adsorption of n-nonadecane (saturated hydrocarbon), toluene and 3-methylphenanthrene (aromatic hydrocarbons), and porphyrin (resin) in the slits of clay minerals (montmorillonite, kaolinite, and illite with 10 nm slit apertures) at 358 K and 30 MPa was evaluated through molecular dynamics simulations. The single adsorption layer thicknesses of different hydrocarbons adsorbed on montmorillonite were 0.31-0.48 nm. The total thickness and volume proportion of the adsorption layers, which can be used as a measure of adsorption capacity, were 0.96-1.57 nm and 12.0-23.5%, respectively, and varied with the hydrocarbon component in the order of resin > aromatic > saturated hydrocarbon. The hydrocarbon adsorption capacity of montmorillonite is stronger than that of illite and kaolinite. The structural morphology of hydrocarbon molecules, in addition to the adsorbent pore size, strongly affects adsorption behavior. The adsorption of the long-chain alkane n-nonadecane occurred with minimal distinction between layers. This previously predicted disorder was seen to increase with distance from the mineral surface. The adsorption capacity increased with the polarity of the hydrocarbon component owing to the induction of van der Waals forces, which are reduced along with the Coulomb force at greater distances between the hydrocarbon and clay minerals. Adsorptive affinities are important for crude oil flow rates. Shale oil contains more high-adsorptive oil fractions, making it less fluid and difficult for production. Although this study profiles the nanoscale adsorption behavior of hydrocarbons, it can also function as a meaningful reference for the assessment of shale oil fluidity.
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