New filter material sorts molecules by shape

MIT Technology Review : Oil refining entails sorting hydrocarbon molecules by size and shape. At a typical refinery, an energy-intensive distilling process separates the crude oil into fractions of various molecular sizes. Further processing or the use of additives is required to create fuels of specific octane levels. A new metal-organic material developed by Jeffrey Long of the University of California, Berkeley, and his colleagues eliminates the need for distillation or additives by sorting molecule size and shape in one step. By varying the metals and organic molecules in the material, researchers can change the size and shape of the pores in it and the way the pores interact with specific molecules. The material that Long and his colleagues made is a lattice of microscopic triangular tunnels designed to sort five different types of six-carbon atom hydrocarbon molecules that determine octane ratings. When the six atoms form a linear structure, a low octane fuel, they move slowly through the material. Larger, branching hydrocarbon arrangements move more quickly through the tunnels. The hydrocarbons pass through the material in regular intervals, making separation easy. The material is still experimental and would have to be produced at larger scales and incorporated into current refineries before it could be effectively commercialized.