Researchers in Germany have developed an intensive process for preparing ionic liquids using a continuously operating micro-reactor system. Previously their manufacture on a large scale has been limited by the use of batch procedures.

Daniel Waterkamp and colleagues at the Centre for Environmental Research and Technology UFT, University of Bremen prepared 1-butyl-3-methylimidazolium bromide that was more than 99% pure at a rate of nine kilograms per day. They achieved a space-time yield 24 times that achieved using a conventional batch reactor.

'In the field of ionic liquid production ineffective procedures still dominate. Many researchers, including members of our working group, have already demonstrated the advantages of unit operations at the micro scale,' said Waterkamp.

'The next logical step was to combine our experience in chemistry and engineering and prove the applicability of micro reaction technology for ionic liquid synthesis at the production scale,' he said.

Another advantage of the process is that the addition of solvent to control the reaction is unnecessary, as the high specific surface area of the reaction system carries away any heat generated during the process.

A theoretical model of the reaction showed that further optimisation of the process could potentially lead to space-time yields a hundred times those of a batch reactor.

Joanna Stevens