Toward the Understanding of Chemical Absorption Processes for Post-Combustion Capture of Carbon Dioxide: Electronic and Steric Considerations from the Kinetics of Reactions of CO2(aq) with

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• 作者：William Conway ; Xiaoguang Wang ; Debra Fernandes ; Robert Burns ; Geoffrey Lawrance ; Graeme Puxty ; Marcel Maeder
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：January 15, 2013
• 年：2013
• 卷：47
• 期：2
• 页码：1163-1169
• 全文大小：295K
• 年卷期：v.47,no.2(January 15, 2013)
• ISSN：1520-5851

文摘

The present study reports (a) the determination of both the kinetic rate constants and equilibrium constants for the reaction of CO₂(aq) with sterically hindered amines and (b) an attempt to elucidate a fundamental chemical understanding of the relationship between the amine structure and chemical properties of the amine that are relevant for postcombustion capture of CO₂ (PCC) applications. The reactions of CO₂(aq) with a series of linear and methyl substituted primary amines and alkanolamines have been investigated using stopped-flow spectrophotometry and ¹H NMR measurements at 25.0 掳C. The specific mechanism of absorption for each of the amines, that is CO₂ hydration and/or carbamate formation, is examined and, based on the mechanism, the kinetic and equilibrium constants for the formation of carbamic acid/carbamates, including protonation constants of the carbamate, are reported for amines that follow this pathway. A Br酶nsted correlation relating the kinetic rate constants and equilibrium constants for the formation of carbamic acid/carbamates with the protonation constant of the amine is reported. Such a relationship facilitates an understanding of the effects of steric and electronic properties of the amine toward its reactivity with CO₂. Further, such relationships can be used to guide the design of new amines with improved properties relevant to PCC applications.