Evaluation of a lab-scale ionic liquid synthesis using life cycle assessment

Abstract

This study presents the life cycle assessment (LCA) for the synthesis of 1-ethyl-3-methylimidazolium acetate, [C₂C₁im][OAc], an ionic liquid (IL) that is often studied at lab-scale. Three pathways were evaluated using SimaPro® LCA software. At a 3–4 g scale, the anion-exchange route had the lowest environmental impact (99.8 Pt), followed closely by the dimethyl carbonate route (102.0 Pt), while the silver acetate route had an increased impact score (133.5 Pt). Scaling up the dimethyl carbonate route using a high-pressure benchtop reactor considerably improved its sustainability (14.8 Pt). Hotspots were identified and recommendations for improvements are given. Comparison is made with several green metrics. The investigation acts as a guide for sustainable ionic liquid synthesis in the laboratory, promoting critical evaluation of established synthetic work-flows using methodologies such as LCA, and the holistic implementation of green chemistry principles in daily working practices.