Improved Solvent Formulations for Efficient CO2 Absorption and Low-Temperature Desorption

This experimental study describes efficient CO2 capture by 2-amino-2-methyl-1-propanol (AMP)/piperazine (PZ) in ethylene glycol monoethyl ether (EGMEE, 2-ethoxyethanol) containing approximately 15 wt?% of water. In these experiments, the solvent is continuously circulated between the absorber (packed-bed reactor at 30, 40, or 45?degrees C) and the desorber (at 80, 85, or 90?degrees C). The CO2solvent reaction equilibria have been investigated by using 13C NMR spectroscopy, which provides confirmatory evidence that the formation of mono- and biscarbamate derivatives of PZ accounts for most of the CO2 absorbed by the AMP/PZ/EGMEE/H2O blend. The solid-state structures of AMP carbamate and of the carbonate salt of protonated AMP have been determined by using XRD. Both AMPCO2- and CO32- species completely convert to the monoalkyl carbonates on dissolving the respective salts in methanol, ethanol, or ethylene glycol.