- Title
- Protonation constants and thermodynamic properties of amino acid salts for CO₂ capture at high temperatures
- Creator
- Yang, Nan; Xu, Dong-Yao; Wei, Chiao-Chien; Puxty, Graeme; Yu, Hai; Maeder, Marcel; Norman, Sarah; Feron, Paul
- Relation
- Industrial & Engineering Chemistry Research Vol. 53, Issue 32, p. 12848-12855
- Publisher Link
- http://dx.doi.org/10.1021/ie502256m
- Publisher
- American Chemical Society
- Resource Type
- journal article
- Date
- 2014
- Description
- Amino acid salts have greater potential for CO₂ capture at high temperatures than typical amine-based absorbents because of their low volatility, high absorption rate, and high oxidative stability. The protonation constant (pKₐ) of an amino acid salt is crucial for CO₂ capture, as it decreases with increasing absorption temperature. However, published pKₐ values of amino acid salts have usually been determined at ambient temperatures. In this study, the pKₐ values of 11 amino acid salts were determined in the temperature range of 298-353 K using a potentiometric titration method. The standard-state molar enthalpies (ΔH⁰m) and entropies (ΔS⁰m) of the protonation reactions were also determined by the van't Hoff equation. It was found that sarcosine can maintain a higher pKₐ than the other amino acids studied at high temperatures. We also found that the CO₂ solubilities and overall mass-transfer coefficients of 5 m' sarcosinate (moles of sarcosine per kilogram of solution) at 333-353 K are higher than those of 30% MEA at 313-353 K. These results show that some possible benefits can be produced from the use of sarcosine as a fast solvent for CO₂ absorption at high temperatures. However, the pronotation reaction of sarcosine is the least exothermic among those of all amino acids studied. This could lead to a high regeneration energy consumption in the sarcosinate-based CO2 capture process.
- Subject
- protonation constants; amino acid salts; CO₂; pKₐ; thermodynamic properties
- Identifier
- http://hdl.handle.net/1959.13/1296785
- Identifier
- uon:19303
- Identifier
- ISSN:0888-5885
- Language
- eng
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