The leading process for the post combustion capture (PCC) of CO2 from coal-fired power stations and hence reduction in greenhouse gases involves capture by aqueous amine solutions. Of the reactions that occur in solution, which include CO2 hydration, de-protonation of carbonic acid, amine protonation and carbamate formation, the protonation of the amine in the absorber and its subsequent de-protonation in the stripper involve the greatest enthalpy changes. In this study, protonation constants (reported as log(10)K(prot)) of selected series of primary, secondary and tertiary alkanolamines/amines over the temperature range 288-318 K are reported. Selected series studied involve primary, secondary and tertiary mono-, di- and tri-alkanolamines, secondary amines including heterocyclic species, and both -CH2OH and -CH2CH2OH substituted piperidines. van't Hoff analyses have resulted in the standard molar enthalpies, Delta H-m degrees, and molar entropies, Delta S-m degrees, of protonation. Trends in Delta H-m degrees are correlated with systematic changes in composition and structure of the selected series of amines/alkanolamines, while Delta H-m degrees-Delta S-m degrees plots generated linear correlations for the mono-, di-, and tri-alkanolamines, the -CH2OH and - CH2CH2OH substituted piperidines, and the alkylamines. These relationships provide a guide to the selection of an amine(s) solvent for CO2 capture, based on a greater difference in log(10) K-prot between the absorber and stripper temperatures. (C) 2012 Elsevier Ltd. All rights reserved.