Kinetics of the Reversible Reaction of CO2(aq) and HCO3鈥?/sup> with Sarcosine Salt in Aqueous Solution

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• 作者：Qunyang Xiang ; Mengxiang Fang ; Hai Yu ; Marcel Maeder
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：October 25, 2012
• 年：2012
• 卷：116
• 期：42
• 页码：10276-10284
• 全文大小：472K
• 年卷期：v.116,no.42(October 25, 2012)
• ISSN：1520-5215

文摘

Aqueous sarcosine salts are fast carbon dioxide (CO₂) absorbents suitable for use in postcombustion CO₂ capture in coal-fired power plants. We have developed a detailed reaction scheme including all the reactions in the sarcosine鈥揅O₂鈥搘ater system. All unknown rate and equilibrium constants were obtained by global data fitting. We investigated the temperature-dependent rate and equilibrium constants of the reaction between aqueous CO₂ and sarcosine using stopped-flow spectrophotometry, by following the pH changes over the wavelength range 400鈥?00 nm via coupling to pH indicators. The corresponding rate and equilibrium constants ranged from 15.0 to 45.0 掳C and were analyzed in terms of Arrhenius, Eyring, and van鈥檛 Hoff relationships. The rate constant for the reaction between CO₂ and sarcosine to form the carbamate at 25.0 掳C is 18.6(6) 脳 10³ M^鈥? s^鈥?, which is very high for an acyclic amine; its activation enthalpy is 59(1) kJ mol^鈥? and the entropy is 33(4) J mol^鈥? K^鈥?. In addition, we investigated the slow reaction between bicarbonate and sarcosine using ¹H nuclear magnetic resonance spectroscopy and report the corresponding rate and equilibrium constants at 25.0 掳C. This rate constant is 5.9 脳 10^鈥? M^鈥? s^鈥?.