Nonaqueous amine-based absorbents by replacing water with organic solvents have potential advantages of low energy penalty and reduced amine degradation for CO 2 capture. An advanced nonaqueous system of 2-(butylamino)ethanol (BAE) with 2-butoxyethanol (EGBE) was proposed for low-energy consumption CO 2 capture. EGBE was selected as a green cosolvent because of its superior properties over the reported organics and water. A comprehensive study on CO 2 capture performance has been performed for secondary alkanolamine nonaqueous systems such as 2-(methylamino)ethanol (MAE), 2-(ethylamino)ethanol (EAE), and BAE and their aqueous counterparts. Product species in CO 2 -loaded solutions were identified by 13 C nuclear magnetic resonance and Fourier transform infrared spectroscopy. Regeneration energy consumption was also evaluated using a modified method and compared with that of conventional aqueous monoethanolamine (MEA). Results demonstrated that the aqueous 5.0 M secondary amine absorbents had higher absorption capacity and larger cyclic capacity than their nonaqueous counterparts. The desorption efficiency for both systems was in a descending order: BAE > EAE > MAE. Surprisingly, the cyclic capacity of aqueous and nonaqueous BAE systems was about 180 and 100% higher than that of aqueous MEA, respectively. The underlying reasons were also discussed. CO 2 can react with these amines, forming unstable carbamates and protonated amines in the EGBE solvent, whereas it forms bicarbonate species in addition to ionic couples in aqueous solutions. The regeneration heat duty of nonaqueous EGBE-based secondary amine absorbents was about 45−55% lower than that of aqueous MEA (3.82 MJ kg −1 CO 2 ). In addition, the feasibility of low-temperature desorption makes the BAE/EGBE absorbent a compelling solution for energy-saving CO 2 capture technology using low-grade industrial waste heat.

Solubility of N2O and CO2 in pure 2-butoxyethanol (2-BE) was determined in a stirred equilibrium cell at temperatures ranging from 283.2 to 333.2 K and correlated as an exponential function of temperature. Ratios of solubility of CO2 to N2O in several reported solvents were found to be strongly dependent on the order of solvent dielectric constants. Solubility of N2O in 2-(butylamino)­ethanol (BAE) and the binary blends of 2-BE and BAE was measured over the temperature range from 283.2 to 333.2 K and with BAE concentration from 6.5 to 65.4 mass%. N2O solubility data were well represented by correlation models with AARDs within 0.8%. Physical solubility of CO2 in a nonaqueous 2-BE/BAE system can be estimated using the N2O analogy method.

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