Ionic Liquids: Review of their Current and Future Industrial Applications and their Potential Environmental Impact

Background: Over the last two decades, thousands of scientific papers and many patents have been written relating to applications of ionic liquids, a family of compounds that garnered such huge interest due to their reputation as "green chemicals". This work reviews the recent literature to investigate the progress ionic liquids have made in their transition from academia to full-scale application in a variety of industries. Methods: For this review, keywords related to ionic liquids and their possible applications were used to search patent databases such as Google patents. The recent patents thus discovered were tabulated and sorted by application, and the most significant patents were identified. For each application of ionic liquids identified in the patent search, an additional review of the recent scientific literature was carried out, focussing on the relevant ionic liquids and their potential environmental impact. Results: Patents involving ionic liquids were found for various industrial applications, including in chemical industry production technologies, nanotechnology, gas storage and environmental remediation. Despite the widespread interest of the chemical industry, which hopes to improve the environmental sustainability of their technologies by utilising ionic liquids, to date, only a handful of full-scale processes which utilise ionic liquids have been successfully commercialised. That said, a large number of pilot studies have been carried out in recent years, and 62 patents and 270 scientific texts are summarised herein and other industrial applications are also approaching the market. Conclusion: The properties of ionic liquids inhibit their entry into the atmosphere. However, their annual production is expected to increase drastically, raising urgent questions about their environmental impact, especially in water bodies. More research is thus required to identify and mitigate any risks ionic liquids might pose to the environment.