Scientists at the US Department of Energy’s Los Alamos National Laboratory are developing a new high-temperature polymer membrane to separate and capture carbon dioxide, preventing its escape into the atmosphere.
The polymeric-metallic membrane under development at Los Alamos is said to be operationally stable at temperatures as high as 370 degrees Celsius. To date, polymer membranes commercially available for gas separation are limited to maximum operating temperatures of 150 degrees Celsius.
Industrial processes that produce carbon dioxide operate at temperatures as high as 375 degrees Celsius, and to capture the carbon dioxide it first must be separated from other gases.
‘Current technologies for separating carbon dioxide from other gases require that the gas stream be cooled to below 150 degrees Celsius, which reduces energy efficiency and increases the cost of separation and capture,’ said Jennifer Young, principal investigator for Los Alamos’ carbon dioxide membrane separation project. ‘By making a membrane which functions at elevated temperatures, we increase the practicality and economic feasibility of using membranes in industrial settings.’
According to Young, developing an efficient and economically feasible membrane from membrane materials is difficult because the membrane materials are expensive, and there is a trade-off between productivity and selectivity. On the other hand, less expensive commercially available polymer membranes are effective only up to 150 degrees Celsius.
‘Our approach is to improve upon conventional technology,’ said Young. ‘The most promising application of this technology in terms of the carbon sequestration program is the separation of hydrogen from carbon dioxide in synthesis gas; however, the technology is not limited to this particular gas pair. For example, it might also be useful in the separation of carbon dioxide from methane. ‘
Young’s team developed the high-temperature membrane based on the polymer polybenzimidazole (PBI) combined with a porous metallic support.
According to Young, the resulting composite membrane outperforms other high-temperature membranes in terms of selectivity for the separation of hydrogen from carbon dioxide; has the highest demonstrated operating temperature of polymer-based membranes, 370 degrees Celsius; is chemically resistant; and is easily processed.
The combination of metallic support and polymer film to form thin-film composite membranes also allows the membrane to be effective at higher pressures than conventional membranes.