By combining carbon-capturing solids and liquids to develop a “slurry,” scientists from École polytechnique fédérale de Lausanne, University of California-Berkeley and Beijing have created a carbon capture method that is relatively simple to implement on a large scale, economical and energy efficient, according to Nature Communications.
Currently, carbon capture is primarily done by either using powder-like solid materials that “stick” to carbon dioxide, or by using liquids that absorb the CO2. However, both methods are prohibitive because of engineering demands, cost and overall energy-efficiency.
The liquid approach uses liquid amine solutions, which can absorb CO2 from the atmosphere. On a large scale, the system uses two columns, one for capturing CO2 and the other for releasing it from the liquid in an energy inefficient process called regeneration.
The solids approach uses metal-organic frameworks — fine powders whose particles are made up of metal atoms that are connected into a 3D structure with organic linkers. However, despite a lower process cost, transportation using this method is costly. Lead researcher Bernard Smit likens it to trying to walk with a plate of baby powder.
The breakthrough carbon-capture process the research scientists created uses a mixture of both solid and liquid in solution called a slurry. The solid part of the slurry is a metal organic framework called ZIF-8, which is suspended in a 2-methylimidazole glycol liquid mixture.
ZIF-8 is a good material for carbon-capturing slurries, because it displays excellent solution, chemical stability and thermal stability, which is important for repeated regeneration cycles. ZIF-8 crystals have narrow pores that are smaller than the diameter of glycol molecules, which prevents them from entering.
According to Smit, pumping slurry is much easier than transporting a pile of baby powder, and the same technologies can be used for heat integration as the liquid process.
Carbon capture has become a priority in research. In June, a University of Alabama professor was granted a patent for using a form of liquid salt to scrub CO2 from emissions. That same month Rice University scientists announced they had invented a porous material that separates carbon dioxide from natural gas at wellheads.
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