Polythene sheets

Sheets of polythene, a ubiquitous material derived from ethylene, protect crops. Credit: Laurance Richardson/Alamy

Materials science

A crystal palace for useful molecules

Mineral eases purification of an important raw material.

A crystalline material has been developed that easily separates mixtures of several commercially important chemicals and could drastically improve production of a widely used feedstock.

The hydrocarbon ethylene is central to myriad chemical processes. But its production from natural gas is energy-intensive because ethylene molecules are difficult to separate from other gases, such as ethane.

A team at Spain’s Polytechnic University of Valencia, and at ExxonMobil sites in Annandale, New Jersey, and Baytown, Texas, has developed a new variety of a crystalline mineral called a zeolite. The zeolite’s intricate structure includes zigzag channels that lead to heart-shaped cavities. Molecules of both ethane and ethylene gas diffuse into the channels, but only ethylene stays inside the cavities.

The authors hope that their material will spur interest in zeolites as materials for difficult industrial separations.