Hydrophobic Deep Eutectic Solvent and Glycolipid Biosurfactant as Green Asphaltene Inhibitors: Experimental and Theoretical Studies

Abstract

Precipitation of asphaltenes in porous media undesirably influences oil recovery due to pore clogging and subsequent wettability alteration. This study reports, primarily, the potential application of two environmentally-friendly chemicals, a hydrophobic deep eutectic solvent (DES) and a glycolipid biosurfactant known as rhamnolipid (RL), as asphaltene precipitation inhibitors. While DES was prepared by mixing glycerol, as its hydrogen bond donor (HBD) component, with methyltrioctylammonium chloride, as its hydrogen bond acceptor (HBA) component, RL was extracted from the native strain of Pseudomonas aeruginosa. The inhibition potential of these green chemicals was then characterized from experimental and theoretical perspectives. In the experimental part, the inhibition efficacy of both chemicals was initially confirmed based on the precipitation experiments. Next, filtration and optical microscopy provided evidence of chemical interaction between inhibitors and asphaltenes. To further illustrate the structural alteration of asphaltenes recovered from the inhibitor-included solutions, Fourier transform infrared and elemental analyses were conducted. Results revealed that the dominant inhibition mechanism of DES was the cracking/dissolution of asphaltene particles compared to peptization in the case of RL. Increased oxygen content and H/C ratio plus the decreased aromaticity index of the asphaltenes recovered from the DEScontaining solution compared with those of the raw asphaltene were indications of the dissolution mechanism. In addition, comparing the performance of synthesized chemicals with a conventional inhibitor, dodecylbenzene sulfonic acid, revealed the preferable performance of the chemicals. In the theoretical part, the propensity of asphaltene precipitation was studied using the surface energy concept based on the extended DLVO theory. The results showed that acid−base interactions among different subcomponents of the surface energy played a key role in retarding asphaltene precipitation by decreasing the attraction force between similar asphaltene particles, further supported by the concepts of work of cohesion and adhesion.

Study of Asphaltene Deposition in the Presence of a Hydrophobic Deep Eutectic Solvent Using XDLVO Theory

“…Additionally, the combination of ILs and DESs can add benefits of both chemicals, such as the hydrophobic attraction of ILs to asphaltenes via their alkyl tail and the electron transfer ability of DESs with asphaltenes, to the asphaltene inhibition systems. In this regard, the idea of combining ILs and DESs was investigated, for the first time, in recent papers published by the present authors in which the efficacy of an IL-based HDES, methyltrioctylammonium chloride:glycerol (1:2), as asphaltene precipitation inhibitor was characterized. , It should be pointed out that this HDES was screened out of several HDESs and ILs which their performance against only inhibition of precipitation has been reported. , This study discerns the application of the same HDES as a green inhibitor , of asphaltene deposition on a dolomite rock surface from a surface energy viewpoint. As far as the present authors are aware, there are no other studies concerning asphaltene deposition from a surface energy perspective using the concept of extended DLVO (XDLVO) theory.…”

“…IL-based HDES, methyltrioctylammonium chloride:glycerol (1:2), was prepared by mixing methyltrioctylammonium chloride (Aliquat 336) (≥98%, Acros Organics, USA) as IL with glycerol (≥99 wt %, Sigma-Aldrich) at a specified temperature (90 °C) until a transparent liquid was formed . The prepared HDES could be considered environmentally friendly since it is nontoxic, biodegradable, with no bioaccumulation; hence it can be called a green inhibitor. ,,, Figure shows the chemical structure of HDES. The synthesized HDES showed strong hydrophobic properties, as discussed in other studies. , …”

“…The prepared HDES could be considered environmentally friendly since it is nontoxic, biodegradable, with no bioaccumulation; hence it can be called a green inhibitor. ,,, Figure shows the chemical structure of HDES. The synthesized HDES showed strong hydrophobic properties, as discussed in other studies. , …”

“…The application of chemicals as inhibitors has extensively been investigated. − An effective inhibitor must retard asphaltenes’ deposition by interacting with asphaltene or producing a steric hindrance via their alkyl chains . In this regard, different experimental techniques, including filtration, spectroscopy, UV–vis spectrophotometry, and light scattering, can be used to evaluate the effectiveness of inhibitors against asphaltene aggregation and deposition.…”

“…In addition, novel methods like quartz crystal microbalance (QCM) based technique have recently been proposed as faster and more accurate methods . Many studies have categorically shown that asphaltenes are strong acceptors of hydrogen bonds. ,, Therefore, electron pairs of the heteroatoms in the asphaltenes’ structure could participate in the electron transfer activity of these heavy molecules.…”