Making membranes

Engineers have developed a method for creating membranes from crystal sieves called zeolites that could increase the energy efficiency of chemical separation processes and enable higher production rates.

Researchers led by Michael Tsapatsis, chemical engineer at the University of Minnesota, developed a rapid-heating treatment to remove structural defects in zeolite membranes that limit their performance, a problem that has plagued the technology for decades.

'Using membranes rather than energy-intensive processes such as distillation and crystallisation could have a major impact on industry,' said Rosemarie Wesson, programme officer at the US National Science Foundation (NSF).

The discovery could increase the energy efficiency of producing important chemical solvents such as xylene and renewable biofuels such as ethanol and butanol.

Researchers create zeolite membranes by growing a film of crystals with small organic ions that are added to help determine which molecules can pass through the material. Then they slowly heat the zeolite film in a process called calcination to decompose the ions and open the pores.