Ionic Liquids as Extraction Desulfurizers and Corrosion Inhibitors: Experimental and Theoretical Studies

Ionic liquids (ILs) have received widespread attention in the field of green desulfurization in the past few years due to their excellent desulfurization ability and infinite potential for designability. However, the additional costs and environmental issues faced when dealing with ILs with degraded desulfurization performance have limited their practical applications. To solve the reuse problem of degraded ILs, this study analyzed the feasibility of using ILs as extraction desulfurizers and corrosion inhibitors in refineries using methods such as liquid chromatography, electrochemical impedance spectroscopy, quantum chemistry, and molecular dynamics simulation. The results indicated that 1-hydroxyethyl-3-hexylimidazolium bromide gave a great thiophene desulfurization efficiency of 50.82% and an excellent corrosion inhibition efficiency of 98.29%. After undertaking desulfurization tasks, the IL could continue to act as an interface-type inhibitor to adsorb on the Q235 surfaces, hindering aqueous electrolyte attack and thus inhibiting the corrosion rate of refining equipment. Its adsorption obeyed the Langmuir isotherm. Improving the electron donating ability, side chain interaction, imidazolium ring, and thiophene interaction, as well as the adsorption of thiophene S atoms on long side chains of IL cations, while suppressing the interaction between the imidazolium ring and n-heptane and the adsorption of n-heptane on the long side chains, could further increase the corrosion inhibition and desulfurization performance of ILs. Using ILs as extraction desulfurizers and corrosion inhibitors is expected to solve environmental and safety issues in the refining process and reduce the adverse effects of high prices on the practical application of ILs.