When it comes to greenhouse gases, few are as potent as methane - by some estimates, 25 times as much as the equivalent amount of carbon dioxide. A group of researchers from the University of Texas at Austin has now found a way to separate carbon dioxide from natural gas - which consists primarily of methane - using a modified polymer.
The so-called thermally rearranged (TR) plastic essentially blocks natural gas from moving through hourglass-shaped pores located within it - allowing carbon dioxide to diffuse several hundred times faster through them than in conventional membranes. As Benny Freeman, a professor of chemical engineering and a co-author on the related Science article, explained: "The plastic chains move, and as they do, they open up gaps that allow certain gas molecules to wiggle through the plastic." In addition, the TR plastic is four times as effective in sifting carbon dioxide out through the pores.
Freeman noted that using this modified plastic would save processing plants 500 times the amount of space currently being taken up to process natural gas. Moreover, it would allow them to "lose less natural gas in their waste products," a critical property given natural gas' contribution to global warming.
The scientists hope to see it implemented in oil reservoirs (to recapture waste carbon dioxide) and used to isolate natural gas from decomposing rubbish. It could prove especially useful in separating carbon dioxide from power plant emissions since it can handle temperatures upward of 600°F. In fact, they discovered that the elevated temperatures helped give the plastic its unique properties.
Even more promising is their applicability to fuel cells. As Ho Bum Park, the lead author on the study and a postgraduate student, explained: "These membranes also show the ability to transport ions since they are doped with acid molecules, and therefore could be developed as fuel cell membranes. However, a lot of research still needs to be done to understand gas and ion transport through these membranes."
Via ::University of Texas Office of Public Affairs: New Membrane Strips Carbon Dioxide From Natural Gas Faster and Better (news release), ::Science: Polymers with Cavities Tuned for Fast Selective Transport of Small Molecules and Ions (magazine)