Seven chemical separations to change the world

Most industrial chemists spend their days separating the components of large quantities of chemical mix­ tures into pure or purer forms. The processes involved, such as distillation, account for 10–15% of the world’s energy consumption. Methods to purify chemicals that are more energy efficient could, if applied to the US petroleum, chemical and paper manufactur­ ing sectors alone, save 100 million tonnes of carbon dioxide emissions and US$4 billion in energy costs annually (see ‘Cutting costs’). Other methods would enable new sources of materials to be exploited, by extracting metals from sea water, for example. Unfortunately, alternatives to distillation, such as separating molecules according to their chemical properties or size, are under­ developed or expensive to scale up. Engi­ neers in industry and academia need to develop better and cheaper membranes and other ways to separate mixtures of chemicals that do not rely on heat. Here, we highlight seven chemical separation processes that, if improved, would reap great global benefits. Our list is not exhaustive; almost all commercial chemicals arise from a separation process that could be improved.