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Summary: In the present study, the reaction kinetics of carbon dioxide (CO2) with two blends of N‐methyldiethanolamine; potassium salts of taurine and potassium salts of glycine were investigated. The experiments were performed using a stopped flow apparatus over a range of temperature varying from 293 to 313 K. The concentration of solution was varied from 0.2 to 0.8M in different proportions of potassium salts of taurine and glycine. For both cases, the overall reaction rate constant (kov) increased with increased temperature and amino acid salts proportions in the blends. Results also indicated that addition amino acid salts (AAS) could improve the overall reaction rate of methyldiethanolamine (MDEA) with CO2 by more than 100 times. The kinetics data were interpreted using the widely accepted mechanisms namely; zwitterion and termolecular mechanisms. An average absolute deviation of 8.8% was observed for both mechanisms applied to MDEA‐KTau blend, while an AAD% of 7.4 and 7.2 were observed for the case of MDEA‐KGly system when applying the zwitterion and termolecular mechanisms, respectively. The results showed that blends of MDEA and potassium salts amino acids react faster with CO2 compared to conventional amine systems. Hence, the use of both potassium salts of taurine and glycine as rate promotors can significantly enhance the reactivity of MDEA toward CO2. [ABSTRACT FROM AUTHOR]

The apparent protonation constant of an amino butanol (AB) and its carbamate formation constant in the CO2-H2O-AB system were determined at T = 298.15-328.15 K, and at various ionic strengths up to 0.2 mol.L-1 by potentiometric titration. The Debye-Huckel equation was used to extrapolate the protonation constants to zero ionic strength. The variation of the thermodynamic equilibrium constant for carbamate formation with temperature was modeled according to the relationship of log10 - K1 = 280.91/T - 0.1105, while the temperature dependency of the amine protonation constant was correlated by log10 K2 = 1926.53/T + 2.9482. Van't Hoff type plots of the pK values showed linear relationships indicating that the standard enthalpy changes of reaction are constant over this range of temperatures. Hence, our current findings are crucial for designing efficient unit operations involving separation of CO2 from natural or flue gases. [ABSTRACT FROM AUTHOR]

The use of amino acids as potential solvents for carbon dioxide (CO 2 ) capture has been considered by a number of researchers. However, very little is known about the kinetics and mechanism of amino acids-CO 2 reactions. In this work, we investigate the reactions of three amino acids ( l -Arginine, Glycine and Sarcosine) with CO 2 in aqueous media using stopped-flow conductivity technique. The experiments were performed at temperatures between 293 and 313 K and amino acids concentrations were in the range of 0.05–0.2 molar. The overall rate constants (k ov ) was found to increase with increased amino acid concentration and solution temperature. Both zwitterion and termolecular mechanisms were used to model and interpret the data. However, the Zwitterion mechanism was found to be the preferred one. From the stopped-flow results at pH around 6, we found that neutral l -Arginine, Glycine and Sarcosine react with CO 2 (aq) with k (M −1 s −1 ) = 2.81 × 10 10 exp( − 4482.9 T ( K ) ), k (M −1 s −1 ) = 3.29 × 10 13 exp( − 8143.7 T ( K ) ) and k (M −1 s −1 ) = 3.90 × 10 13 exp( − 7991.0 T ( K ) ) respectively. The corresponding activation energies are 37.28 kJ mol −1 , 67.71 kJ mol −1 And 66.44 kJ mol −1 respectively. A comparison between the kinetics of the three amino acids showed that Arginine exhibits highest reaction rate with CO 2 followed by Sarcosine and then Glycine. The technique and results obtained from this work can be used as strong tools in the development of efficient new solvents for the removal of CO 2 from flue and industrial gases. [ABSTRACT FROM AUTHOR]

Carbon dioxide managements and its association with global worming remains a major concern among governments and the scientific community, with novel, energy efficient and more affordable technologies topping the research agendas. Despite the importance of amino acids, their use as reaction promoters in combination with alkanolamines has been overlooked by researchers. Here, stopped-flow technique was used for the first time to measure the pseudo-first-order reaction kinetics of CO 2 with various aqueous mixtures of N-methyldiethanolamine (MDEA) and glycine (Gly). The experiments were performed at a temperature range from 293 to 313 K and a total amine concentration up to 2 mol/l. The activation energy for CO 2 -MDEA reaction obtained from this work was found to be 49.24 kJ/mol, and the overall rate constants (k ov ) increased with increasing temperature and with increasing proportion of Glycine in the solution mixture. Using the zwitterion mechanism to interpret the CO 2 -MDEA-Gly reaction, we found that the glycine reacts with CO 2 (aq) with k 2 (M −1 s −1 ) = 2.40 × 107 exp(−3887.5/T(K)) with an activation energy of 22.95 kJ/mol. [ABSTRACT FROM AUTHOR]

Carbon capture and management plays an important role in the development of new technologies to mitigate anthropogenic global warming. In this work, for the first time, the kinetics of CO2 with aminobutanol (AB) using a stopped-flow method are presented. The temperature changed from 293 to 313 K for a total amine concentration up to 0.3 mol/L. The kinetics data were analyzed using both zwitterion and termolecular reaction mechanisms with a preference to the zwitterion mechanism. AB was found to react with CO2 (aq) with k2 (M-1 s-1) = 2.93 × 109 exp(-4029.9/T (K)) with an estimated activation energy of 33.51 kJ/mol. Compared to other popular amines, CO2 reaction with aminobutanol has faster kinetics than that of CO2 with diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) but slower than that with monoethanolamine (MEA). The Brønsted relationship between the rate constant (k2) and pKa values was found to predict well the rate constant with an average absolute deviation (AAD) of 6.1%. [ABSTRACT FROM AUTHOR]