Efficient CO2 absorption and low temperature desorption with non-aqueous solvents based on 2-amino-2-methyl-1-propanol (AMP)

• CO2 capture by non-aqueous solvents as amine carbamate and alcohol carbonate.
• Low stripping temperature combined with high CO2 absorption efficiency.
• The role of unstable AMP carbamate as a promoter of alcohol carboxylation.
• The identification and quantification of the species based on 13C NMR analysis.

In the present study, an efficient process for CO2 capture using some AMP–alkanolamine blends, namely DEA, MDEA, MMEA, DIPA, in non-aqueous solvents has been described. The solvents used are mixtures of ethylene glycol or 1,2-propandiol with either methanol or ethanol. Additionally, either pure 1-propanol or diethylene glycol monomethyl ether have been also employed. Throughout the whole set of experiments, the amine solutions were continuously circulated in a closed cycle between the absorber (set at 20 °C) and the desorber (set at 65, 70, 75, 80 °C). The CO2 absorption efficiency at equilibrium is in the range 73.1–95.9%. The carbon containing species in the amine–CO2–alcohol equilibria were analyzed by 13C NMR spectroscopy showing that they originate from alcohol and/or amine carboxylation. The AMP–DEA–1-propanol–CO2 system gives a solid compound that has been identified as the carbamate derivative of AMP, [(AMPH)(AMPCO2)], from its 13C solid state NMR spectrum and confirmed by single crystal X-ray structure determination. [(AMPH)(AMPCO2)] instantaneously dissolves in methanol, ethanol and ethylene glycol affording the respective monoalkyl carbonate. The lower stripping temperature of the studied absorbents offers several potential advantages with respect to conventional aqueous solutions of the same alkanolamines, yet preserving comparable efficiency.

CO2 is captured by AMP–amine blends in non-aqueous solvents as amine carbamate and alcohol carbonate which are analyzed using in situ 13C NMR spectroscopy. Solid AMP carbamate, that has been isolated and characterized, reacts with alcohols affording the corresponding alkyl carbonates.Figure optionsDownload as PowerPoint slide