Deep eutectic solvents as alternative green solvents for the efficient desulfurization of liquid fuel: A comprehensive review

Abstract

Increase in the requirement of energy consumption has been followed by a consistent rise in sulfur emission with economic and health issues. Moreover, it considerably decreases the efficacy of developed emission control systems of diesel engines, thus ultimately harms the atmosphere. It leads to a strict sulfur discharge limit to approximately 15 ppm and sequentially served as a goal for investigating different desulfurization technologies. Hydrodesulfurization, a conventional refinery desulfurization process is operated at higher pressure and temperature, employing expensive catalysts and hydrogen gas. This review aims to consider the merits and demerits of main areas of the substitute desulfurization processes, comprising adsorptive, extractive, oxidative, and biodesulfurization and comprehensively discuss the role of DESs emphasizing on the factors affecting in extractive and oxidative desulfurization. Different factors such as DESs selection, extraction temperature, extraction time, DESs regeneration, and multistage extractions are considered that affect the desulfurization efficiency. Deep eutectic solvents explored in 2001, a less toxic solvent have been keenly investigated as an alternative solvent for extractive desulfurization since 2013. DESs showed a higher capability for sulfur elimination. Low synthetic cost and economical raw materials, less solvent to feed ratio, and valuable green characteristics show DESs suitable for the desulfurization process.