Coarse-grained molecular dynamics study for optimizing the solvent-to-feed mass ratio in diesel purification by LLE using an imidazolium-based ionic liquid

Resumen

To determine the optimal solvent-to-feed mass ratio in a liquid–liquid extraction (LLE) process, four systems comprising the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) and an impure diesel model represented by dodecane were constructed. The impurities considered were pyridine, thiophene, and toluene. The systems were simulated using coarse-grained molecular dynamics (CGMD) with the MARTINI 3 force field. The amount of IL was kept constant, while the amount of impure diesel was varied to obtain solvent-to-feed mass ratios of 1:0.5, 1:1, 1:2, and 1:3. In all four systems, the impure diesel composition was identical, consisting of 70% dodecane and 10% of each impurity. The optimal ratio was determined by extraction efficiency, distribution ratio, and selectivity. The 1:2 system exhibited the highest extraction efficiency for all three impurities, reaching 49% for toluene, 77% for thiophene, and 84% for pyridine. The distribution ratio followed the same pattern as the extraction efficiency, with the highest values also observed for the 1:2 system for all three impurities. Pyridine exhibited the highest distribution ratio, reaching 9.0, followed by thiophene (5.4) and toluene (1.9). Selectivity increased with increasing impure diesel mass, indicating a stronger preference of the IL for the impurities. The highest selectivity values were obtained for pyridine, indicating its preferential extraction over the other system components. The RDF analysis for the optimized system followed the same trend with the pyridine closer to the [BMIM] confirming a strong affinity.