Improving carbon capture from power plant emissions with zinc- and cobalt-based catalysts

Abstract

A carbonic anhydrase mimic converting CO2 to carbonic acid, deprotonated under highly basic conditions, and being converted to a carbamate upon reaction with monoethanolamine, a solvent reported for carbon capture reactions.

Carbon Dioxide Sequestration by Using a Model Carbonic Anhydrase Complex in Tertiary Amine Medium

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Globally,t he elevation of carbon dioxide (CO 2 )l evels due to the anthropogenic effect poses as erious threat to the ecosystem. [10] Recently, CA model complexesw ere combined with aqueous solutions of amine and carbonate to increaset he absorbance of CO 2 for the post-combustion process. Herein, it is proposed to improve CO 2 sequestration by using model complexes based on the enzymec arbonic anhydrase (CA) in aqueous tertiary amine medium.

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“…Hence, it is important to control and/or mitigate the level of CO 2 in the atmosphere,w hich necessitatesn ovel tools. [8,10] When CA models are used in highly concentrated amine for the post-combustion process, the following problems arise:a nion coordination to the metal center inhibits the fourth catalytic cyclea nd generates weak dissociation of bicarbonate from the catalytic centerd ue to the electrond eficiency at the metal center. The effect of substituents on the model CA model complexes on CO 2 absorption and desorption was determined by using as topped-flow spectrophotometer to follow pH changes through coupling to pH indicator and ac ontinuous stirred-tank reactor (CSTR).…”

“…[7] The active site of CA consists of one zinc atom coordinated with three histidine and H 2 O/ OH À .D espite the highest CO 2 hydration activity,C Ai sn ot as uitable catalyst for industrial CO 2 sequestration processes as ar esult of cost and poor stability under handling conditions. [8,10] When CA models are used in highly concentrated amine for the post-combustion process, the following problems arise:a nion coordination to the metal center inhibits the fourth catalytic cyclea nd generates weak dissociation of bicarbonate from the catalytic centerd ue to the electrond eficiency at the metal center. [7] The CA-based model complexes employed in basic mediumw ere [Zn(cyclen)(H 2 O)][ClO 4 ] 2 (cyclen = 1,4,7,10-tetraazacyclododecane), [8] which is aw ell-known active CA model, [9] and zinc complexes containing salen-like ligands.…”

“…One approach to overcome the drawbacks of using CA in CO 2 sequestration is to design ac atalytic system that mimics the active site of CA which hydrates CO 2 for use on an industrial scale. [8,10] When CA models are used in highly concentrated amine for the post-combustion process, the following problems arise:a nion coordination to the metal center inhibits the fourth catalytic cyclea nd generates weak dissociation of bicarbonate from the catalytic centerd ue to the electrond eficiency at the metal center. [10] Recently, CA model complexesw ere combined with aqueous solutions of amine and carbonate to increaset he absorbance of CO 2 for the post-combustion process.…”

The salt-based catalytic enhancement of CO2 absorption by a tertiary amine medium

“…Hence, the tertiary amine methyldiethanolamine (MDEA) is commonly employed in CO 2 absorption processes; it has two further advantages: a lower level of solvent degradation, and less energy must be supplied to the stripper to regenerate the absorbent. [16][17][18] Very recently, CO 2 absorption through the use of the carbonic anhydrase (CA) enzyme [19][20] and its model complexes [21][22][23] in tertiary amine solution has been demonstrated, and found to exhibit enhanced absorption of CO 2 hydration. However, the use of CA model complexes in highly concentrated tertiary amine medium results in anion coordination with the metal center, which inhibits the fourth catalytic cycle in the generation of bicarbonate, and the CA enzyme is expensive and unstable under industrial conditions.…”