Kinetics of absorption of carbon dioxide in aqueous MDEA solutions with carbonic anhydrase at 298 K

In present work the absorption of carbon dioxide in aqueous N-methyldiethanolamine (MDEA) solutions with and without the enzyme carbonic anhydrase has been studied in a stirred cell at 298 K, with MDEA concentrations ranging from 0.5 to 4 kmol m−3 and carbonic anhydrase concentrations ranging from 0 to 2275 g m−3, respectively. The obtained experimental results show that carbonic anhydrase significantly enhances the absorption of carbon dioxide in aqueous MDEA solution. When the enzyme is present in the absorption solution, MDEA concentration does not materially influence on the absorption rate. Therefore, the enzyme does not enhance the reaction of CO2 with MDEA, since the rate of this reaction is a function of the MDEA concentration. Rather, the enzyme enhances the reaction of carbon dioxide with water. In the presence of enzyme this reaction is not only first order in CO2, but also first order in water. Thus, carbonic anhydrase may provide a solution for the efficient capture of carbon dioxide from flue gases by significantly increasing the kinetics of its absorption in MDEA, a tertiary amine which requires less energy for regeneration than monoethanolamine (MEA), the current industry benchmark.

► Successful application of carbonic anhydrase in carbon dioxide capture.
► Enzyme has no influence on carbon dioxide solubility in amine solution.
► Reactions of CO2 with amine and CO2 with water occur parallel.
► Amine mainly acts as proton acceptor in regeneration reaction of enzyme.
► Enzymatic reaction is first order in carbon dioxide and first order in water.