Table salt is a commonplace ingredient in the kitchen, but a different kind of salt is at the forefront of chemistry innovation. Low-temperature molten salts known as ionic liquids are said to be "greener" and safer than traditional solvents. According to an article in Chemical & Engineering News, the weekly newsmagazine of the American Chemical Society, ionic liquids are on the cusp of transforming how fibers, fuels and other industrial materials are made.
Ionic liquids are salts that contain an organic cation, and an organic or inorganic anion. Their irregular structure gives them a lower melting point than other salts, making them easier to work with in an industrial capacity. In addition, they are less flammable than other solvents and can be implemented in a variety of applications. In particular, they have been used as solvents in chemical processes and biomass refining, catalysts in chemical synthesis and electrolytes in lithium-ion batteries. Notably, in 2018 the First Lady of Finland wore a dress made of birch fibers processed using ionic liquids. The simple, closed-loop process of making the garment had no chemical discharge, providing an alternative to fossil fuel-based fibers, such as polyester.
The biggest challenge for widespread implementation of ionic liquids is economics. Although some companies are working to reduce the cost of producing ionic liquids by scaling up production, the many potential uses for the molten salts has prevented focused investment in large-scale, profitable solutions. However, industrial giants are getting into the game: Chevron is implementing ionic liquid-based technology in a new refinery in Salt Lake City, where it will replace traditional hydrofluoric acid catalysts for simpler and safer handling. While there is still much work to be done in this area, chemists are optimistic that liquid salts will usher in a new wave of scientific innovation.