Molecular Dynamics Simulation: The Behavior of Asphaltene in Crude Oil and at the Oil/Water Interface

Abstract

Carboxyl asphaltene is commonly discussed in the petroleum industry. In most conditions, electroneutral carboxyl asphaltene molecules can be deprotonated to become carboxylate asphaltenes. Both in crude oil and at the oil/water interface, the characteristics of anionic carboxylate asphaltenes are different than those of the carboxyl asphaltenes. In this paper, molecular dynamics (MD) simulations are utilized to study the structural features of different asphaltene molecules, namely, C5 Pe and anionic C5 Pe, at the molecular level. In crude oil, the electroneutral C5 Pe molecules prefer to form a steady face-to-face stacking, while the anionic C5 Pe molecules are inclined to form face-to-face stacking and T-shaped II stacking because of the repulsion of the anionic headgroups. Anionic C5 Pe has a distinct affinity to the oil/water interface during the simulation, while the C5 Pe molecules persist in the crude oil domain. A three-stage model of anionic C5 Pe molecules adsorbed at the oil/water interface is finally developed.

Molecular dynamic simulation of asphaltene co-aggregation with humic acid during oil spill

“…The sharp peaks observed at $0.4 nm indicated the parallel stacking of asphaltenes due to pp interactions in the aromatic regions which agreed with previous experimental and simulation data (Pisula et al, 2005;Jian et al, 2014). The small peaks located at 0.75 and 1.1 nm suggested the T-shape stacking as demonstrated by Gao et al (2014). Moreover, the intensity of interactions between LHA and asphaltenes was independent on the type of asphaltenes in context of this study, because the number of asphaltene-LHA intermolecular contacts differed very slightly between ASP1 and ASP2 (Fig.…”

“…3). The interface is identified as the region where the water density is 10-90% of the value in its bulk phase (Frost and Dai, 2011;Gao et al, 2014), which is highlighted as dotted line in Fig. 3.…”

Fractionation of Asphaltenes in Understanding Their Role in Petroleum Emulsion Stability and Fouling

“…Molecular dynamics simulation studies confirmed that asphaltene aggregation results in the formation of complex structures both in the bulk and at the oil-water interface. [43][44][45][46] The strong selfaggregation of asphaltenes facilitates the adsorption of asphaltenes at oil-water interfaces, which is crucial for the stabilization of oil-water petroleum emulsions, and also the adsorption of asphaltenes onto mineral and metallic surfaces, which leads to plugging and fouling through entire oil production chains. 38 Copyright 2010 American Chemical Society.…”

An interface-analyzing technique to evaluate the heavy oil swelling in presence of nickel oxide nanoparticles

“…Recently, studies of prevention methods of asphaltene precipitation are attended very much [18]. Vanishing-Interfacial-Tension (VIT) is a new method, which could be used for understanding the asphaltene precipitation onset point [19][20][21][22][23]. This accurate method needs a small amount of sample for laboratory experiments [24][25][26].…”

“…In this method, IFT would drastically increase after the onset point [27,28]. Precipitation mechanism, its rate, and onset point could be determined by analyzing the slope changes in the graph of IFT versus pressure [29,[21][22][23][24][25]. In addition, the VIT method gives information about the drop volume either at a specific pressure and temperature or during their increasing.…”