Experimental study on carbamate formation in the AMP–CO2–H2O system at different temperatures

• AMP–CO2–H2O system was studied quantitatively by 13C NMR.
• Carbamate formation was observed even at low loadings.
• Carbamate formation was almost temperature independent in the range tested.
• The apparent carbamate stability constant was estimated at 25, 35 and 45 °C.
• A method of splitting HCO3−/CO32− and amine/amineH+ is proposed.

Carbamate formation in the 30 wt% of 2-amino-2-methyl-1-propanol (AMP) system at different CO2 loadings and temperatures was studied via nuclear magnetic resonance (NMR) spectroscopy. The results indicate that the main species in this system are AMP/AMPH+, AMPCO2− and HCO3−/CO32−. The carbamate was also observed at low loadings and the apparent carbamate stability constant was estimated based on the experimental concentrations of the species from NMR analysis. Carbamate formation was found to have weak temperature dependence in the range tested (25–45 °C). To distinguish within the AMP/AMPH+ and HCO3−/CO32− pairs, the amine protonation constant, the dissociation constant of carbonic acid from literature, and pH measurements for different ionic strengths were all employed. All the data were correlated with ionic strength and temperature.The accuracy of the carbamate stability constant determined from the concentration measurements will depend on pKa, ionic strength (I) used to calculate the speciation and on the uncertainty in the species concentration determinations from NMR, particularly for the carbamate species at low CO2 loadings and high temperature.