Experimental and mechanistic study of bio-based solvent Cyrene for de-aromatization of model diesel

Abstract

Liquid-liquid extraction is an important technique for separating aromatic and alkane hydrocarbons. The toxicity and pollution problems of traditional solvents are difficult to solve, and the use of green bio-based solvents for diesel fuel dearomatization is of great significance to solve energy and environmental problems. In this paper, Cyrene, a low toxicity, low cost, green composition bio-based solvent, was selected as an extractant to study its ability to remove mono- and bicyclic aromatics from chain alkanes and cycloalkanes, respectively. In addition to the ternary system, the extraction effects under various experimental conditions and multi-component simulated systems were also investigated. The results showed that aromatics and cyclic structures tend to interact more strongly with Cyrene due to differences in solute structure, and therefore polycyclic aromatic hydrocarbons tend to produce larger distribution coefficients. the selectivity coefficients of Cyrene for the four systems were influenced by differences in interaction energies in the order: dodecane/1-methylnaphthalene > dodecane/indene > decahydronaphthalene/1-methylnaphthalene > decahydronaphthalene/indene. At the same time, multi-component simulated oil experiments have demonstrated that Cyrene is equally selective in removing aromatic hydrocarbons from complex components. Quantum chemical calculations were used to investigate the extraction mechanism of Cyrene. The results of Reduced Density Gradient (RDG), Atoms In Molecules (AIM), and Symmetry-Adapted Perturbation Theory (SAPT) energy decomposition proved that the interaction forces between Cyrene and solute molecules are van der Waals forces dominated by dispersion forces and accompanied by some very weak hydrogen bonds. Finally, thermodynamic correlations using the NRTL model were performed to obtain binary interaction parameters for the four systems. The results of this paper indicate that Cyrene, as a new green bio-based solvent, has the potential to be used as an extractant and shows good separation in the removal of long carbon chain aromatic hydrocarbons, and this paper also provides basic data and references for subsequent studies.