Dispersion of Asphaltenes in Petroleum with Ionic Liquids: Evaluation of Molecular Interactions in the Binary Mixture

Ionic liquids containing imidazolium cations 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium nitrate, and 1-methyl-1H-imidazol-3-ium-2-carboxybenzoate were successfully synthesized and employed for the dispersion of asphaltenes in heavy oil, which is becoming a necessity during oil recovery and transportation. Molecular interaction studies indicated that 1-butyl-3-methylimidazolium chloride displayed a small HOMO–LUMO energy gap, which best explains its higher polarizability and reactivity as compared with 1-butyl-3-methylimidazolium nitrate and 1-methyl-1H-imidazol-3-ium-2-carboxybenzoate. Dispersion indices obtained from the experiments were in agreement with the modeling studies. Maximum asphaltene dispersion indices (%) of 78, 70, and 53 were obtained for 1-butyl-3-methylimidazolium chloride,1-butyl-3-methylimidazolium nitrate, and 1-methyl-1H-imidazol-3-ium-2-carboxybenzoate, respectively, when using an ionic liquid-to-asphaltenes molarity ratio of 9:1. The excellent performance displayed by 1-butyl-3-methylimidazolium chloride is based on the thermodynamic interaction energy and HOMO–LUMO energy it holds.