The kinetics of the reaction between CO 2 and methyldiethanolamine in aqueous solutions have been studied using the stopped-flow technique at 288, 293, 298 and 303 K. The amine concentration ranged from 250 to 875 mol·m -3 . The overall reaction rate constant was found to increase with amine concentration and temperature. The acid base catalysis mechanism was applied to correlate the experimentally determined kinetic data. A good agreement between the second order rate constants for the CO 2 reaction with MDEA computed from the stopped-flow data and the values reported in the literature was obtained.
Abstract:The pseudo-first-order rate constants (kOV) for the reactions between CO2 and diethanolamine have been studied using the stopped-flow technique in an aqueous solution at 293, 298, 303 and 313 K. The amine concentrations ranged from 167 to 500 mol·m . The overall reaction rate constant was found to increase with amine concentration and temperature. Both the zwitterion and termolecular mechanisms were applied to correlate the experimentally obtained rate constants. The values of SSE quality index showed a good agreement between the experimental data and the corresponding fit by the use of both mechanisms.Keywords: reaction kinetics, CO2 absorption, kinetic model, diethanolamine, stopped-flow technique Carbon dioxide (CO 2 ) emission is still increasing because of increasing energy demand. This causes that greenhouse effect becomes more intensive and therefore governments, industries and researchers are becoming increasingly interested in CO 2 capture from gas streams. Reactions of carbon dioxide with amines have been used for gas sweetening on a commercial scale for more than 75 years. Stripping carbon dioxide from gas streams with alkanolamines allows also removing the hydrogen sulphide (H 2 S). In these processes the most widely used amines are monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA).Diethanolamine is very popular and reaction kinetics of CO 2 in aqueous DEA was widely investigated. Secondary alkanolamines like DEA react rapidly with CO 2 to form carbamates. The reaction of CO 2 with secondary amines is usually described by the zwitterion mechanism. However, the results of kinetic studies are still confusing and conflicting and there are many discrepancies in the literature concerning the interpretation of the kinetic data. The main reasons of this disagreement are diversity of research methods
Kinetics of the reaction of CO2 and ethylethanolamine (EMEA) in aqueous solutions has been studied using the stopped-flow technique with conductivity detection. Measurements were performed at 288 K, 293 K, 298 K, and 303 K. Amine concentration ranged from 10 mol m−3 to 37.5 mol m−3. The termolecular mechanism was applied to interpret the kinetic data. In this mechanism, carbamate formation occurs in a single-step reaction without the formation of a zwitterion intermediate. An original method of analyzing the experimental data was proposed allowing the derivation of pseudo second order rate constants from the measured kinetic traces. Based on these values, the third order rate constants $$\left( {k_{H_2 O} } \right)$$ of the reaction of CO2, water, and EMEA were derived and correlated by the Arrhenius equation.
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