Molecular dynamics of interfacial crystallization of dodecane on hydroxylated silica surface impacted by H2O and CO2
Molecular dynamics of interfacial crystallization of dodecane on hydroxylated silica surface impacted by H2O and CO2
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DOI：
10.1063/5.0145211
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发表时间：
2023-05-28
影响因子：
4.4
通讯作者：
Bahai, H.
中科院分区：
文献类型：
--
作者：
Chen, C.;Xia, J.;Bahai, H.
使用分子动力学模拟研究了在开采或枯竭油藏中典型温度下纳米孔中十二烷的形态。十二烷的形态被认为是由界面结晶和表面润湿的简化油之间的相互作用，而“蒸发”只起着次要的作用。随着系统温度的升高，形态从孤立的、固化的十二烷液滴变为具有有序层状结构的膜，最后变为含有随机分布的十二烷分子的膜。在水的冲击下的纳米缝中，由于水在二氧化硅表面上的表面润湿中由于静电相互作用诱导的水与二氧化硅的硅烷醇基团之间的氢键而战胜油，因此十二烷分子在二氧化硅表面上的扩散受到这种水限制机制的阻碍。同时，界面结晶增强，导致总是孤立的十二烷“液滴”，随着温度的升高，结晶减弱。由于十二烷与水不混溶，因此十二烷没有逸出二氧化硅表面的机制，并且水和油之间的表面润湿的竞争决定了结晶十二烷液滴的形态。对于纳米缝中的CO2-十二烷体系，CO2在所有温度下都是十二烷的有效溶剂。因此，界面结晶迅速消失。在所有情况下，CO2和十二烷之间的表面吸附的竞争是次要的。溶解机理是一个明确的线索，事实上，二氧化碳是更有效的比水驱油开采枯竭油藏。
The morphology of dodecane in a nanopore at temperatures typical in exploited or depleted oil reservoirs is investigated using molecular dynamics simulation. The dodecane morphology is found to be determined by interactions between interfacial crystallization and surface wetting of the simplified oil, while "evaporation" only plays a minor role. The morphology changes from an isolated, solidified dodecane droplet to a film with orderly lamellae structures remaining within, and finally to a film containing randomly distributed dodecane molecules, as the system temperature increases. In a nanoslit under the impact of water, since water wins against oil in surface wetting on the silica surface due to electrostatic interaction induced hydrogen bonding between water and the silanol group of silica, the spreading of dodecane molecules over the silica surface is impeded by this water confinement mechanism. Meanwhile, interfacial crystallization is enhanced, leading to always an isolated dodecane "droplet," with crystallization weakening as the temperature increases. Since dodecane is immiscible to water, there is no mechanism for dodecane to escape the silica surface, and the competition of surface wetting between water and oil determines the morphology of the crystallized dodecane droplet. For the CO2-dodecane system in a nanoslit, CO2 is an efficient solvent for dodecane at all temperatures. Therefore, interfacial crystallization rapidly disappears. The competition of surface adsorption between CO2 and dodecane is secondary for all cases. The dissolution mechanism is a clear clue for the fact that CO2 is more effective than water flooding in oil recovery for a depleted oil reservoir.