Molecular dynamics simulations to develop novel solvents for deep desulfurization of diesel

Abstract

For the last decade, deep eutectic solvent (DES), a novel solvent, has gathered lots of attention due to their favorable properties such as a low melting point, non-toxicity and low-cost. In this work, a combination of tetrabutylammonium chloride (TBAC), polyethylene glycol (PEG-200), and ferric chloride (FeCl3) at a molar ratio of 4:1:0.05, a metallic based deep eutectic solvent is analyzed using molecular dynamics simulation. The analysis reveals the interactions between the components of DES, which might lead to the formation of the DES, i.e., strong depression in the melting point as compared to the individual component. Further, the solvent was also tested for fuel desulfurization using molecular simulations. For the analysis n-octane was chosen as fuel with ~2000 ppm dibenzothiophene and the results suggest strong absorption of sulfur compounds by the DES. Molecular dynamics simulations were performed using GROMACS to explore different interactions occurring between the components of the DESs and model oil at a molecular level. Interaction energies between compounds and radial distribution functions indicate a strong interaction between the tetrabutylammonium ion with the dibenzothiophene molecule. The given work also shows that the DES can be applied for diesel even with high initial concentration of sulfur content and can be applicable for extraction of different sulfur compounds such as benzothiophene (BT) and thiophene (TS). Additionally, among all tested temperature ranges it was found that use of the room temperature is beneficial for the desulfurization process. Moreover, composition of DES was varied by selectively removing either PEG or FeCl3 from the DES to evaluate the influence of each compound on the efficiency of desulfurization process.