Polymer could improve the separation of gas mixtures

Gas separation is essential for many industrial processes including obtaining nitrogen or oxygen from air and purifying natural gas or hydrogen.

Currently, the most energy-efficient method for separating gases involves polymer membranes. However, most polymers have low permeability or are not selective towards one gas over another. Gas separation would be cheaper and use less energy if polymer membranes could be made both highly permeable and selective.

A team from the School of Chemistry reported in the journal Science details of a new polymer that efficiently separates gas mixtures based on the different sizes of the gas molecules.

The polymer’s molecular structure is very contorted so that it cannot fill space efficiently, leaving gaps for small gas molecules to move through quickly. However, the transport of larger gas molecules is hindered by the polymer’s extreme rigidity so that it acts as an efficient molecular sieve.

The Cardiff’s team’s collaborators at the Institute on Membrane Technology, ITM-CNR, in Italy confirmed that membranes prepared from the polymer are both highly permeable to gases and demonstrate remarkable selectivity for smaller gases such as hydrogen or oxygen over larger gases such as nitrogen or methane.