Kinetics of carbon dioxide and methyldiethanolamine with phosphoric acid

The Kinetics of the reaction between carbon dioxide and methyldiethanolamine (MDEA) were studied in the presence of various amounts of phosphoric acid at 298 K, 308 K, and 318 K. A stirred cell with a known interfacial area was used at atmospheric pressure to measure the volumetric absorption rate of CO2 flowing through the vessel. The addition of phosphoric acid to an aqueous solution of MDEA resulted in a Bronsted acid‐base neutralization reaction. While virtually all of the acid was consumed by the neutralization reaction, a large part of the MEDA remained in its free form. The absorption of carbon dioxide in these solutions was slower than expected, given the amount of free MDEA present. The rate depression in the presence of hydrogen phosphate anions was attributed to the stabilization of the reaction transition state between MDEA, water, and carbon dioxide through charge dispersal.