Comparative life cycle assessment of the use of an ionic liquid ([Bmim]Br) versus a volatile organic solvent in the production of acetylsalicylic acid

Abstract

Ionic liquids have generated interest as a promising green alternative to replace traditional volatile organic solvents, because they can be tailor-made designed for specific applications and exhibit interesting properties such as non-volatility, non-flammability and stability. This work aims to evaluate the potential environmental impacts coming from an ionic liquid: 1-butyl-3-methylimidazolium bromide ([Bmim]Br) using a “cradle to gate” Life Cycle Analysis approach. The environmental profile of [Bmim]Br is compared to a volatile organic solvent (Toluene) in the production of acetylsalicylic acid. The results indicate that the ionic liquid has higher environmental impacts than toluene, especially in the impact categories associated with ecotoxicity. The influence of solvent recovery with promising separation technologies, and the effect of replacing the anion type in the ionic liquid were studied. The results showed that solvent recovery is a crucial parameter that can make the use of ionic liquids an attractive alternative comparable to toluene. Also, the environmental profile of [Bmim]Br was found to be comparable to 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) although the former has lower toxicity than the latter. These results encourage further research on the potential of using ionic liquids as “green solvents”. The use of emerging technologies for recovery/reuse of these novel solvents can help to make the ionic liquids a good substitute to replace volatile organic solvents. This study proposes an approach that can be applied to evaluate the greenness of a wide range of processes, products and emerging technologies.