Role of Ionic Liquid in Asphaltene Dissolution: A Combined Experimental and Molecular Dynamics Study

Abstract

The role of ionic liquid in asphaltene dissolution is studied using experimental characterization techniques, such as optical microscopic imaging analysis, 13C nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy, along with molecular insights achieved using classical molecular dynamics (MD) simulations. The dissolution behavior of the asphaltenes in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]­[PF6]) ionic liquid along with organic solvents, i.e., toluene and hexane, is investigated using optical images. The behavior of asphaltene aggregates in the solvent plus ionic liquid mixture is probed using FTIR and 13C NMR spectroscopic techniques. The structural and dynamical properties of the asphaltene aggregates mainly end-to-end distance, the diffusion coefficient of the asphaltene molecules, and the trajectory density contour of the asphaltene in the solvent plus ionic liquid mixture are probed using MD simulations. It is concluded from our combined experimental–MD study that the ionic liquid plays a key role in asphaltene separation from organic solvents under study.

Probing the Effect of Aliphatic Ionic Liquids on Asphaltene Aggregation Using Classical Molecular Dynamics Simulations

“…It is the distance between one end of the side chain to the other chain end. The end-to-end distance is an important parameter to assess asphaltene aggregation ,, and is calculated by considering the semiflexible side chains within the worm-like chain model . The end-to-end distance of the asphaltene molecule averaged over all asphaltene molecules is evaluated over the production run of MD using the following equation: − , ⟨ h 2 ⟩ = 2 L normalP L 0 [ 1 − false( L normalP / L 0 false) false( 1 − exp ( − L 0 / L P ) false) ] where ⟨ h 2 ⟩ is the mean squared end-to-end distance, L 0 is the extended chain length, and L P is the persistence length.…”

“…Ionic liquids (ILs) are promising candidates and could be used to efficiently separate asphaltenes from crude oil − and can also separate bitumen from the oil sands. − ILs are environmental friendly and highly efficient organic salts because of the properties such as low melting point, good thermal and chemical stability, nonflammability, etc. , Addressing the issue of asphaltene separation using ILs can thus aid in the easy transportation of crude oil.…”

“…In their work, 90% bitumen was recovered in successive extractions. Sakthivel et al 10 performed experimental investigations using ultraviolet−visible (UV−vis) spectrophotometry, Fourier transform-infrared spectroscopy (FTIR), and 13 C-nuclear magnetic resonance (NMR) spectroscopy on the dissolution of asphaltene present in tank bottom sludge using nine aromatic ILs in different organic solvents such as decane, hexane, ethyl acetate, heptane, and toluene. It was shown in their work that the presence of ILs in organic solvents increases the efficiency of disaggregation by more than 50% as compared to the neat solvents.…”

“…It was concluded that with an increase in the alkyl chain length of the IL molecule, the asphaltene aggregation is promoted. Vatti et al 13 performed experimental investigations and MD simulations of 1-butyl-3-methylimidazolium hexafluorophosphate IL and asphaltene. In their study, the role of IL in separating asphaltene from the toluene/hexane solvents was discussed.…”

“…Vatti et al. 13 performed experimental investigations and MD simulations of 1-butyl-3-methylimidazolium hexafluorophosphate IL and asphaltene. In their study, the role of IL in separating asphaltene from the toluene/hexane solvents was discussed.…”