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

Abstract

One of the major constituents of heavy oil is asphaltenes. They are responsible for numerous problems in petroleum downstream and upstream processes, such as catalyst deactivation in heavy oil processing and blocking pipes while transporting crude oil. Probing the efficiency of new nonhazardous solvents in separating asphaltenes from crude oil is key to avoid conventional volatile and hazardous solvents by replacing these conventional solvents with new ones. In this work, we have investigated the efficiency of ionic liquids to separate asphaltenes from organic solvents (such as toluene and hexane) using molecular dynamics simulations. Triethylammonium-dihydrogen-phosphate and triethylammonium acetate ionic liquids are considered in this work. Various structural and dynamical properties are calculated, such as radial distribution function, end-to-end distance, trajectory density contour, and diffusivity of asphaltene in the ionic liquid-organic solvent mixture. Our results explain the role of anions, i.e., dihydrogen-phosphate and acetate ions, in separating asphaltene from toluene and hexane. Our study provides an important revelation about the dominant role played by the IL anion in intermolecular interactions which depends on the type of solvent (i.e., toluene or hexane) in which the asphaltene is present. The anion induces enhanced aggregation in the asphaltene-hexane mixture compared to the asphaltene-toluene mixture. The molecular insights obtained within this study on the role played by ionic liquid anion in asphaltene separation are key for the preparation of new ionic liquids for asphaltene precipitation applications.