Release Time:2019-03-09  Hits:

Indexed by: Journal Papers

Date of Publication: 2015-11-01

Journal: JOURNAL OF ENVIRONMENTAL SCIENCES

Included Journals: CSCD、ISTIC、PubMed、EI、SCIE

Volume: 37

Page Number: 75-82

ISSN: 1001-0742

Key Words: CO2 capture; Amines; Kinetics

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 (E-a) 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 E-a values for all pathways linearly correlate with pK(a) of amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with pK(a) of the amines, i.e. stronger basicity results in less difference in E-a. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design. (C) 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.