Molecular Dynamics Simulations on Extractive Desulfurization of Fuels By Cobalt Chloride/Choline Chloride/Peg-200 Metal Based Deep Eutectic Solvents

Considering environmental issues, desulfurization process is of paramount importance to produce fuel with low sulfur content. In recent decades, novel sustainable deep eutectic solvents (DESs) illustrated high extractive capacity and efficiency in such desulfurization processes. In this work, interactions of metal-based DESs with model oil consisting of thiophenic compounds were analyzed by using molecular dynamic simulation. In particular, a combination of choline chloride (ChCl): polyethylene glycol (PEG-200): cobalt chloride (CoCl₂)at a ratio 1:2:1 and a combination of tetrabutylammonium chloride (TBAC): PEG-200: CoCl₂ at a ratio 1:2:0.25 were simulated, separately, with model oil at 25 ^oC & 1bar. The simulations reveal lower interaction energies between the constituent compounds of MDESs as compared with their pure state supporting the formation of MDES. Furthermore, detailed analysis of the extraction process reveals that both MDES have strong interactions with refractory sulfur compounds in model oil indicating a high desulfurization efficiency. While extraction efficiency weakly correlates with variation in the hydrogen bond acceptor, hydrogen bond donor, it strongly depends on temperature. As DESs are highly viscous, we herein propose a trade-off between adding water to decrease DES’s viscosity and the efficiency of desulfurization. Taken together, the presented herein present mechanism of desulfurization at molecular level and develop guidelines for practical usage of MDESs in the process.