New chemical combination could improve carbon capture.Current methods for C[O.sub.2] capture from flue gases are energy-intensive, and consequently too expensive for most applications. A new solvent/amine system developed at Saint Mary's University St. Mary's University (in French, Université Ste-Marie, in Spanish, Universidad de Santa María) is the name of several universities:
The standard practice is to bubble the gas through a solution of about 20 per cent monoethanolamine (MEA) in water. C[O.sub.2] dissolves and forms an adduct adduct /ad·duct/ (ah-dukt´) to draw toward the median plane or (in the digits) toward the axial line of a limb.
adduct /ad·duct/ (a´dukt) inclusion complex. with the MEA--this releases a proton which must be accepted by a second MEA molecule. The solution is then heated to release gaseous C[O.sub.2] and regenerate the MEA. "The problem with these MEA/water catch-and-release systems is that they have a very high heat capacity," says Jason Clyburne, professor of chemistry at Saint Mary's University. "The catch is very good, but the release is very costly." As a result, it is currently only useful in high-value applications, such as purification of natural gas; for economical greenhouse gas mitigation the cost needs to be reduced significantly.
Clyburne and his team surveyed many alternatives, both for the capture molecule and the solvents. In a paper published in Industrial and Engineering Chemistry Research, they point out that diethylenetriamine (DETA) is similar to MEA, but is much less volatile and contains multiple amine amine (əmēn`, ăm`ēn): see under amino group.
Any of a class of nitrogen-containing organic compounds derived, either in principle or in practice, from ammonia (NH3). groups. This means it doesn't require a second molecule to accept a proton, and can be used in a 1:1 ratio to capture C[O.sub.2], rather than the 2:1 ratio required by MEA. As for the solvent, the team tested various compounds that would be non-volatile, robust under process conditions, and have a lower heat capacity than water. Several ionic liquids were investigated, but in the end a similar performance at much lower cost could be obtained with a commercially-available polymeric solvent.
The new solvent/amine system is undergoing testing, but so far indications are that it will release C[O.sub.2] at significantly lower energies than traditional MEA/water systems. Clyburne has filed a patent application and is collaborating with GreenCentre Canada, a green chemistry commercialization centre in Kingston, Ont., to bring the discovery to market. "My gut feeling gut feeling Intuition, visceral sensation is it won't take very long," says Clyburne.
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