Post-combustion CO2 capture (PCCC) is the most mature technology to reduce emissions of carbon dioxide in the atmosphere. In comparison with the process using monoethanolamine (MEA), numerous studies have been realized in order to optimize efficiency and costs of PCC. Opportunities for improvements are mainly driven by the selection of the solvent. After thermodynamic properties, operating and capital expenses are also affected by the absorption rate of CO2. At this date, understanding of the relationship between the structure of the amine and its kinetics of the reaction with CO2 remains a challenge. The stopped-flow technique with conductivity detection was used in order to generate a large kinetic database of amines. Indeed, this technique provides fast and precise determination of the apparent first-order kinetic constant (k0) over several decades. 59 primary and secondary amines were chosen in different families (alkyl-amines, alcohol-amines, benzyl-amines, nitrile-amines ...) in order to cover the largest range of pKa and steric hindrance, which are identified as two preponderant descriptors for the kinetics. For each amine, the reaction kinetics towards CO2 is characterized by two third-order kinetic constants of an empirical model. A rigourous statistical approach gives the uncertainty on estimated constants. A quantitative structure property relationship (Q.S.P.R.) was built from experimental or calculated molecular descriptors. We introduce a new descriptor of steric hidrance which is strongly correlated to Taft constant. After a statistical hierarchical cluster analysis of the descriptors, we apply a partial least-squares regression method to establish a polynomial model that correlates the kinetic constants with the explanatory variables. This Q.S.P.R. is of particular interest to guide exploration of new amines and focus kinetic studies in representative temperature and concentration conditions of PCCC for selected amines.

Structure-property study of the kinetics of reaction between primary and secondary amines and carbon dioxide in water

246th National Meeting (2013)

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