title: Toward rational design of amines for CO2 capture: Substituent effect on kinetic process for the reaction of monoethanolamine with CO2.
abstract: Amines have been considered as promising candidates for post-combustion CO2 capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO2 is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products (carbamates, carbamic acids and bicarbonate) from amines+CO2 were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO2 based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies (Ea) for the reactions of a range of substituted monoethanolamines with CO2 covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the Ea values for all pathways linearly correlate with pKa of amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with pKa of the amines, i.e. stronger basicity results in less difference in Ea. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China. Electronic address: hbxie@dlut.edu.cn.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Xie
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China.
authors.forename: Ning
authors.initials: N
authors.lastname: He
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Xianhai
authors.initials: X
authors.lastname: Yang
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China. Electronic address: jwchen@dlut.edu.cn.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
mesh_terms: D000588:Amines / Q000737:chemistry*; D001639:Bicarbonates / Q000737:chemistry; D002219:Carbamates / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry* / Q000302:isolation & purification; D015195:Drug Design; D019856:Ethanolamine / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory
chemical_list: D000588:Amines; D001639:Bicarbonates; D002219:Carbamates; D002245:Carbon Dioxide; D019856:Ethanolamine
keywords: Amines; CO(2) capture; Kinetics