Cheaper petrochemicals to be possible with new material

06-Feb-06

A chemical engineering group at The University of Texas at Austin has in laboratory tests designed a membrane material with superior gas-separating ability and tested its ability to successfully separate hydrogen from carbon dioxide and other contaminant gases. The end result of this pocess is development of a rubbery material that can purify hydrogen efficiently in its most usable form for fuel cells and oil refining. This new membrane material could lower the costs of purifying hydrogen for hydrogen-fueled vehicles, an alternative source of energy for running cars and other devices in the future. The membrane material could also replace an expensive step or reduce energy required in current petrochemical processing. 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. A compressed form of the light-weight gas is needed to process fossil fuels and for it to serve as a readily replaceable fuel for fuel cells. The new membrane separates these two gases better than previous membranes, along with additional components such as hydrogen sulfide and water vapor present as occurs in industrial settings. The membrane worked so well that it was 40 times more permeable to (better at separating out) carbon dioxide than hydrogen. Current commercial membranes favor 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 favoring 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.