Functionalized silica nanoparticles within a multicomponent oil emulsion by molecular dynamic study

Abstract

Molecular dynamics simulations were employed to study hydroxylated and functionalized SiO2 nanoparticles (NPs) within a light crude oil under different temperatures. The model oil comprised a combination of aromatics, alkanes, and cycloalkanes, while the hydroxylation, PEGlyation, and sulfonation of the NPs were evaluated. The effects of functional size were considered for PEGlyated NPs. Interestingly, benzene clusters dispersed in the oil phase were formed for all systems studied; clusters of 9 and 11 molecules were the most common. The benzene clusters adsorbed onto the NPs, forming a surrounding shell approximately 10 Å in width. The agglomeration of aromatic molecules was more evident for hydroxylation covering: the density of benzene molecules in the first shell of aromatic molecules surrounding the NPs decreased in the order NP-H, NP-SA, NP-EG, and NP-PEG2 and reached a maximum for hydroxylated NPs, where the hydrocarbons form a first shell of molecules ∼25 Å in width. The density of benzenes is 24% greater than in pristine oil. Compared to other coverings, this effect reduces the NP–oil interfacial tension for the hydroxylated NPs by about 15%. Our results indicated that the adsorption of benzene on NPs and the NPs–oil interfacial tension could be tuned by the NP covering. This degree of control is highly desirable for applications of NPs in enhanced oil recovery processes.