Outstanding materials continue to revolutionize chemical industry

Separation of closely related organic gases needed in high purity as feedstock is one of the large challenges that face the chemical industry today. 

Removal of propane from propylene gas is one of those challenges. High purity propylene is a prerequisite for polypropylene polymer manufacturing.

So far, methods to separate propane from propylene were based on energy-intensive cryogenic distillation or differential adsorption, and have generally showed low to moderate separation owing to the similar physical properties and structural dimensions of the two gases.

Publishing in Science¹, a team of researchers from King Abdullah University for Science and Technology in Saudi Arabia have now introduced a method for complete extraction of propane from propylene using a new class of metal organic frameworks (MOFs) — porous materials made up of metal or metal cluster centers connected together via organic linkers. 

Their material is made up of square shaped grids of nickel-pyrazine forming layers which are bridged by a five-fluorine-atom-niobium moiety. This moiety is large enough to lock the previously freely rotating pyrazine groups in place, resulting in a restricted pore size that excludes propane but not propylene.

“The ability to ultra-fine tune a pore aperture size to allow the separation of two molecules — that are very close in their size — can only pinpoint to the singularity and the uniqueness of MOF chemistry and its potential to address many enduring energy-intensive separations,” says Mohamed Eddaoudi, who led the study.

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