This method has recently been studied at the ISIS Pulsed Neutron and Muon Source and the results published in the journal Nature Chemistry.
The new material, named NOTT-300, has the potential to revolutionise the capture of greenhouse gases. Its predecessors have all been ammonia-based as they are able to bind strongly with carbon, but not without negative effects. These amines release toxic by-products and the removal of carbon from the compound requires large amounts of energy.
In comparison, NOTT-300 lacks negative environmental effects as producing the material doesn’t involve any organic solvents, and removal of the captured carbon is straightforward. Dr Timmy Ramirez-Cuesta from ISIS described the removal of carbon as being similar to Velcro in that the material selectively captures, or ‘sticks’ to the gases from the flue gas in factory chimneys using weak interactions, and holds them until they can be ‘peeled’ off at low pressure and stored. Easy removal holds importance in terms of energy conservation and viability as just lowering the pressure of the system is sufficient to release the captured carbon.
Collaboration between researchers at the University of Nottingham and ISIS has enabled development of this novel material, which consists of a porous metal-organic framework complex, ideal for gas storage separation and storage due to the vast internal surface area.
The efficiency of the capture process is further increased upon saturation of the material, as the exhaust gases are diverted to a second container where the process continues. The full container is disconnected from the system and the carbon dioxide is removed using a vacuum, and collected, after which the regenerated container is reconnected and used repeatedly.
Experiments using a cocktail of gases showed that NOTT-300 captured close to 100 percent of the carbon dioxide. Although the rate could be lower in the ‘dynamic conditions’ of a real power stations, it should still be over 90 percent.
As the material is gas-specific, it takes hold of the harmful gases carbon dioxide and sulphur dioxide, allowing hydrogen, methane, nitrogen and oxygen to pass through. However, it does absorb water vapour which leaves room for further research to overcome this problem. Nonetheless, NOTT-300 still shows a very high uptake of greenhouse gases, with that of sulphur dioxide being the highest ever reported.
Using NOTT-300 to remove unwanted gases, during purification of not only waste but also natural gases, has huge industry potential due to its low cost, environmentally neutral production, and the uptake and release of gases. The researchers are already working with companies within the carbon capture industry in order to commercialise their product.
Martin Schröder et al.
Research date: September 2012
Selectivity and direct visualization of carbon dioxide and sulphur dioxide in a decorated porous host. Nature Chemistry 4, 887-894 (2012)