树脂在高岭石边缘位点吸附的分子动力学模拟：表面去质子化对界面结构的影响,The Journal of Physical Chemistry C

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树脂在高岭石边缘位点吸附的分子动力学模拟：表面去质子化对界面结构的影响
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-10-05 00:00:00 , DOI: 10.1021/acs.jpcc.7b06688
T. R. Zeitler ₁ , J. A. Greathouse ₂ , R. T. Cygan ₂ , J. T. Fredrich ₃ , G. R. Jerauld ₃

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低盐度注水是一种提高采收率的方法，包括将低离子强度的流体注入储油层中，以便将油从下伏地层的矿物表面分离出来。尽管在实践中非常成功，但该方法尚未在分子规模上被完全理解。分子动力学模拟已用于研究表面质子化对粘土矿物边缘表面上阴离子原油成分吸附的影响。一组适用于边缘模拟的原子间电势已应用于与水性纳米孔接触的高岭石（010）表面。去质子化形式的十氢-2-萘甲酸（DHNA ^–）被用作原油的代表性树脂成分，带有一价和二价抗衡离子，以测试低盐度注水实验中观察到的趋势。表面模型包括完全质子化的（中性）和去质子化的（负）边缘位置，这需要实施新的去质子化方案。对于中性和去质子化条件下的高和低DHNA ^–以Na ⁺和Ca ²⁺作为抗衡离子，对高岭石边缘的表面吸附性能进行了研究。DHNA的倾向^-离子与二价（Cα到坐标²⁺），而不是一价（钠⁺离子极大地影响了阴离子的吸附趋势。此外，带净正电的表面位点由于Ca的形成²⁺在去质子化位点导致增加的DHNA ^-吸附。二价阳离子（例如Ca ^2+）能够有效地桥接表面位点和有机阴离子。用一价阳离子（例如Na ^+）取代那些阳离子会减弱桥接机理，从而导致有机物的吸附减少。DHNA下降的一个明显的趋势^-吸附在模拟的Ca观察²⁺被置换的Na ⁺ 对于去质子化的表面，如在低盐度泛滥事件后油从储层中脱离所期望的那样。

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Molecular Dynamics Simulation of Resin Adsorption at Kaolinite Edge Sites: Effect of Surface Deprotonation on Interfacial Structure

Low-salinity water flooding, a method of enhanced oil recovery, consists of injecting low ionic strength fluids into an oil reservoir in order to detach oil from mineral surfaces in the underlying formation. Although highly successful in practice, the approach is not completely understood at the molecular scale. Molecular dynamics simulations have been used to investigate the effect of surface protonation on the adsorption of an anionic crude oil component on clay mineral edge surfaces. A set of interatomic potentials appropriate for edge simulations has been applied to the kaolinite (010) surface in contact with an aqueous nanopore. Decahydro-2-napthoic acid in its deprotonated form (DHNA^–) was used as a representative resin component of crude oil, with monovalent and divalent counterions, to test the observed trends in low-salinity water flooding experiments. Surface models include fully protonated (neutral) and deprotonated (negative) edge sites, which require implementation of a new deprotonation scheme. The surface adsorptive properties of the kaolinite edge under neutral and deprotonated conditions have been investigated for low and high DHNA^– concentrations with Na⁺ and Ca²⁺ as counterions. The tendency of DHNA^– ions to coordinate with divalent (Ca²⁺) rather than monovalent (Na⁺) ions greatly influences adsorption tendencies of the anion. Additionally, the formation of net positively charged surface sites due to Ca²⁺ at deprotonated sites results in increased DHNA^– adsorption. Divalent cations such as Ca²⁺ are able to efficiently bridge surface sites and organic anions. Replacing those cations with monovalent cations such as Na⁺ diminishes the bridging mechanism, resulting in reduced adsorption of the organic species. A clear trend of decreased DHNA^– adsorption is observed in the simulations as Ca²⁺ is replaced by Na⁺ for deprotonated surfaces, as would be expected for oil detachment from reservoir formations following a low-salinity flooding event.

更新日期：2017-10-05

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