The amount of bicarbonate is a very important factor for energy consumption in solvent regeneration in CO2 capture process. More bicarbonate in rich amines will lead to lower energy cost in CO2 desorption process. To get a preciously knowledge of the formation of bicarbonate in tertiary amines for design a better absorbent for CO2 capture

a series of tertiary amines such as N-diethylethanolamine (DEEA)

1-dimethylamino-2-propanol (1DMA2P)

1-diethylamino-2-propanol (1DEA2P)

3-dimethyl-amino-1-propanol (3DMA1P)

N-methyldiethanolamine (MDEA)

dimethylmonoethanolamine (DMMEA) and triethanolamine (TEA) with various CO2 loading at 1 mol·L-1 were investigated using 13C NMR technology at 293.15 K. The amount of bicarbonate was calculated by the chemical shift of bicarboante/carboante in 13C NMR spectra. The results showed that the order of the amount of bicarbonate in those tertiary amines is DMMEA > MDEA > 3DMA1P > 1DMA2P > TEA > DEEA > 1DEA2P. Considering the effects of electron density of nitrogen atom (N) and the steric hinderance in those tertiary amines to the formation of bicarbonate in those aqueous tertiary amines solution

it can be concluded that 1) the aqueous 3DMA1P solution produced more bicarbonate compared to DMMEA for its nearer distance of OH to N; 2) the less hydroxyalkyl and one more methyl in amine molecular structure connected to N in MDEA compared to TEA led to more bicarbonate generation; 3) a smaller alkyl connected to N in DMMEA molecular structure compare to DEEA resulted in more bicarbonate was generated in aqueous DMMEA solution; and 4) one more methyl branch existed in 1DMA2P and 1DEA2P molecular structures compared to 3DMA1P and DEEA

respectively

leading to less bicarbonate generation.