Abstract
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–Hückel 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.
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Abbreviations
- MEA:
-
Monoethanolamine
- DEA:
-
Diethanolamine
- AP:
-
3-Amino-1-propanol
- AB:
-
Amino butanol
- α :
-
Moles of KHCO3 per mole of amino butanol
- V NaOH :
-
Volume of NaOH (mL)
- AMH+ :
-
Protonated amino butanol
- AMe:
-
Amino butanol at equilibrium
- AMCOO− :
-
Amino butanol carbamate
- HCO −3 :
-
Bicarbonate ion
- CO 2−3 :
-
Carbonate ion
- K 1 :
-
Equilibrium constant for carbamate formation (L·mol−1)
- K prot :
-
Equilibrium constant for protonation (L·mol−1)
- I :
-
Ionic strength (mol·L−1)
- T :
-
Temperature (K)
- K app :
-
Apparent equilibrium constant
- γ i :
-
Activity coefficient of species i
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Acknowledgement
This paper was made possible by an NPRP Grant # 7-1154-2-433 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.
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Mahmud, N., Benamor, A., Nasser, M.S. et al. Carbamate Formation and Amine Protonation Constants in 2-Amino-1-Butanol–CO2–H2O System and Their Temperature Dependences. J Solution Chem 47, 262–277 (2018). https://doi.org/10.1007/s10953-018-0726-z
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DOI: https://doi.org/10.1007/s10953-018-0726-z