Extraction of N- and S-compounds in gasoline and diesel from ionic liquids: A molecular dynamics study

Abstract

The extraction of nitrogen and sulfur compounds from gasoline and diesel, using ionic liquids, is conducted through liquid-liquid molecular dynamics simulations. The novel united atom parameters of pyridine, benzene and thiophene which possess a constant dipole moment successfully reproduce the experimental dielectric constant and solubility in water. These molecular parameters are transferred to simulate toluene and dibenzothiophene. Regarding polar liquids, the coexisting densities and surface tension as functions of temperature align excellently with experimental data. The liquid density and surface tension of modeled diesel and gasoline also match experimental data well although the viscosity is underestimated. Ionic liquids comprise positive ions of imidazolium, pyrrolidinium, pyridinium and trimethyl ammonium varying in hydrocarbon chain length. The anion is bis(trifluoromethylsulfonyl)imide. It has been discovered that the new parameters significantly enhance the extraction of nitrogen and sulfur compounds from hydrocarbon mixtures compared to simulation results from TraPPE-UA force field where the molecules possess zero molecular dipole moment. The extraction efficiency of ionic liquids aligns excellently with experimental results at room temperature.