title: Kinetics of the reversible reaction of CO2(aq) and HCO3(-) with sarcosine salt in aqueous solution.
abstract: Aqueous sarcosine salts are fast carbon dioxide (CO(2)) absorbents suitable for use in postcombustion CO(2) capture in coal-fired power plants. We have developed a detailed reaction scheme including all the reactions in the sarcosine-CO(2)-water 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 CO(2) and sarcosine using stopped-flow spectrophotometry, by following the pH changes over the wavelength range 400-700 nm via coupling to pH indicators. The corresponding rate and equilibrium constants ranged from 15.0 to 45.0 °C and were analyzed in terms of Arrhenius, Eyring, and van't Hoff relationships. The rate constant for the reaction between CO(2) and sarcosine to form the carbamate at 25.0 °C is 18.6(6) × 10(3) M(-1) s(-1), which is very high for an acyclic amine; its activation enthalpy is 59(1) kJ mol(-1) and the entropy is 33(4) J mol(-1) K(-1). In addition, we investigated the slow reaction between bicarbonate and sarcosine using (1)H nuclear magnetic resonance spectroscopy and report the corresponding rate and equilibrium constants at 25.0 °C. This rate constant is 5.9 × 10(-3) M(-1) s(-1).
authors.affiliation: State Key Laboratory for Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, PR China.
authors.forename: Qunyang
authors.initials: Q
authors.lastname: Xiang
authors.forename: Mengxiang
authors.initials: M
authors.lastname: Fang
authors.forename: Hai
authors.initials: H
authors.lastname: Yu
authors.forename: Marcel
authors.initials: M
authors.lastname: Maeder
mesh_terms: D001639:Bicarbonates / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D007700:Kinetics; D012492:Salts / Q000737:chemistry; D012521:Sarcosine / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D001639:Bicarbonates; D012492:Salts; D012996:Solutions; D014867:Water; D002245:Carbon Dioxide; D012521:Sarcosine