Green ionic liquids and deep eutectic solvents for desulphurization, denitrification, biomass, biodiesel, bioethanol and hydrogen fuels: a review

The fossil fuel industry faces issues of atmospheric pollution by sulphur and nitrogen compounds, and emerging competition from electricity, solar, wind and hydrogen sectors. As a consequence, green solvents such as ionic liquids and deep eutectic solvents have been recently developed for alternative fuel purification. Deep eutectic solvents are usually more efficient and better biodegradable, whereas ionic liquids display qualities for safety and optimization. Some ionic liquids and deep eutectic solvents allow a 100% removal efficiency of sulphur and nitrogen compounds from petroleum. Biodiesel yields up to 98.1% are reached using green solvents. Pretreatment of biomass with green solvents has been found to increase by 50% the bioethanol yield.