Hydrogen Fuel Comes Closer to Reality

This member of a new family of membrane materials with superior gas-separating ability could lower the costs of purifying hydrogen for hydrogen-fuelled vehicles. The membrane material could also replace an expensive step in current petrochemical processing, or reduce how much energy the step requires.

The membrane differs structurally and functionally from previous options, with a key advantage being its ability to permit hydrogen to remain compressed at high pressure. Researchers tested flat, disk-shaped versions of the material for its ability to separate different mixtures of hydrogen and carbon dioxide gases at different temperatures. They used the three common temperatures for industrial hydrogen purification: 95 degrees, 50 degrees and minus 4 degrees Fahrenheit.

The new membrane not only separated these two gases better than previous membranes, but did so when additional components such as hydrogen sulfide and water vapour were present as occurs in industrial settings. The membrane worked so well that it was 40 times better at separating out carbon dioxide than hydrogen.

In contrast, current commercial membranes favour the transport of hydrogen, a small molecule, over larger carbon dioxide molecules. This process results in hydrogen being transferred to a low-pressure environment that requires expensive recompression of the gas before use.

The new membrane avoids this recompression step by favouring the transport of larger, polar gas molecules as a result of the polar nature of the polymer materials making up the membrane. The polar, reverse-selective materials based on ethylene oxide interact better with polar gases such as carbon dioxide than with smaller, nonpolar hydrogen gas, which is left behind in a high-pressure state.

COMPAMED.de; Source: University of Texas at Austin