Thursday, May 02, 2013

New materials to capture methane

Methane capture in zeolite SBN. Blue represents adsorption sites, which are optimal for methane (CH4) uptake. Each site is connected to three other sites (yellow arrow) at optimal interaction distance.

Scientists at Lawrence Livermore National Laboratory(LLNL)  and UC Berkeley and have discovered new materials to capture methane, the second highest concentration greenhouse gas emitted into the atmosphere.
Unlike carbon dioxide, the largest emitted greenhouse gas, which can be captured both physically and chemically in a variety of solvents and porous solids, methane is completely non-polar and interacts very weakly with most materials.
"Methane capture poses a challenge that can only be addressed through extensive material screening and ingenious molecular-level designs," Maiti said.
Methane is far more potent as a greenhouse gas than CO2. Researchers have found that the release of as little as 1 percent of methane from the Arctic alone could have a warming effect approaching that being produced by all of the CO2 that has been pumped into the atmosphere by human activity since the start of the Industrial Revolution.
Methane is emitted at a wide range of concentrations from a variety of sources, including natural gas systems, livestock, landfills, coal mining, manure management, wastewater treatment, rice cultivation and a few combustion processes

Zeolites are unique structures that can be used for many different types of gas separations and storage applications because of their diverse topology from various networks of the framework atoms. In the team's simulations, one specific zeolite, dubbed SBN, captured enough medium source methane to turn it to high purity methane, which in turn could be used to generate efficient electricity.
"We used free-energy profiling and geometric analysis in these candidate zeolites to understand how the distribution and connectivity of pore structures and binding sites can lead to enhanced sorption of methane while being competitive with CO2 sorption at the same time," Maiti said.

Other zeolites, named ZON and FER, were able to concentrate dilute methane streams into moderate concentrations that could be used to treat coal-mine ventilation air.

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