Review of current technologies and future trends in ionic liquid-based systems for efficient desulfurization

The desulfurization of fossil fuels is crucial to reducing sulfur dioxide (SO₂) emissions, which contribute to air pollution and acid rain. Traditional hydrodesulfurization (HDS) methods are energy-intensive and costly due to the use of hydrogen. Other desulfurization approaches such as oxidative desulfurization, extractive desulfurization and electrochemical desulfurization offer alternative milder operating condition solution and are often more effective for ultra-low sulfur removal. These approaches utilize various materials as catalysts or electrolytes, and recently ionic liquids have emerged as highly effective materials for this application. This review explores the use of ionic liquids (ILs) as a sustainable catalyst or electrolyte for various non-HDS desulfurization methods. ILs offer unique advantages, including low volatility, thermal stability, conductivity and tunable properties, which enable selective solubilization of sulfur compounds under milder conditions. This work examines various IL types (imidazolium, pyridinium, phosphonium, and metal-based ILs), evaluating their efficiency in sulfur removal, regeneration potential, and environmental impact. The review also discusses the integration of ILs with advanced desulfurization technologies, highlighting their capacity for achieving ultra-low sulfur content while reducing emissions and processing costs. Despite challenges such as high viscosity and regeneration issues, IL-based desulfurization presents a promising direction for cleaner fuel production.