The combustion of fossil fuels to generate energy has a significant externality cost of releasing enormous amounts of carbon dioxide (CO2) into the atmosphere. The CO2 gas has a greenhouse effect of reflecting infrared radiation back to earth, causing temperatures to rise and climates to change dramatically. With the Paris greenhouse gas emission accords signed last November, the United States and most other countries have pledged to reduce CO2 emissions appreciably by 2030. One important strategy to meet this goal is the capture and storage of CO2. The development of CO2 capture technology at Pacific Northwest National Lab (PNNL) has seen tremendous success from a collaborative effort between computational and experimental scientists in the area of carbon capture solvents. These solvents are used to trap CO2 at the source and possess key chemical properties that allow for facile capture and release for sequestration while having minimal impact on the cost of energy. Our combined efforts have been directed to identify target molecules that would internalize hydrogen bonding of carbon dioxide binding organic liquids (CO2BOLs), a class of switchable ionic solvents, in order to realize cost savings in the capture process. These solvents have lower viscosities, lower release temperatures, and higher binding affinities, all of which reduce the energy needs for CO2 capture. A new synthetic route has been identified to produce new classes of CO2BOLs that were previously unobtainable from established synthetic methodology. The new synthesis involves the key steps of condensing various diamines with cyanogen bromide to generate the guanidine core, and then performing a controlled alkylation with the guanidine nucleophile to various custom electrophiles (epoxides) to produce the target compounds. The synthesis is modular, allowing for functional groups on the diamine and epoxide to be easily exchanged in a convergent synthesis of four steps, longest linear route, with good to excellent yields. A second class of new binding organic liquids has also been identified for study involving the use of amines with different hydrogen bond acceptors in close proximity. This class of compounds can be accessed from commercially available materials, and rapidly synthesized in a couple of steps, to provide a diverse library of a third generation of single molecule carbon dioxide capture solvents.

Computational aided design and synthesis of advanced carbon capture solvents

253rd National Meeting (2017)

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