Energy-Efficient CO₂ Capture Using Nonaqueous Absorbents of Secondary Alkanolamines with a 2-Butoxyethanol Cosolvent

Abstract

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.

CO2 absorption and microwave regeneration with high‐concentration TETA nonaqueous absorbents

“…investigated the absorption–desorption cycles with 0.5 M DETA/NMP using microwave heating, and the results showed that the system had a relatively stable cycling performance. Ping et al 27 . reported that the regeneration energy consumption of nonaqueous 2‐(butylamino)ethanol (BAE)/2‐butoxyethanol (EGBE) was significantly reduced to about 1.73 MJ kg –1 CO 2 , which is about 55% lower than that of aqueous MEA under the same operating conditions using microwave heating.…”

“…24,25 Zhang et al 26 investigated the absorption-desorption cycles with 0.5 M DETA/NMP using microwave heating, and the results showed that the system had a relatively stable cycling performance. Ping et al 27 reported that the regeneration energy consumption of nonaqueous 2-(butylamino)ethanol (BAE)/2-butoxyethanol (EGBE) was significantly reduced to about 1.73 MJ kg -1 CO 2 , which is about 55% lower than that of aqueous MEA under the same operating conditions using microwave heating. Li et al 28 investigated the characteristics of microwave regeneration for nine TETA nonaqueous solutions at 0.6 M, and the results showed that the heating rate of a solution in the microwave was primarily affected by its viscosity, dielectric constant, and heat capacity.…”

Densities, Viscosities, and Excess/Deviation Properties of the Ternary System 2-(Methylamino)ethanol + Dimethyl Sulfoxide + Water and the Binary Subsystems

“…5−11 In comparison to MEA, secondary alkanolamines, 2-(methylamino)ethanol (MAE), with a methyl group connected to a N atom show comparative reaction kinetics, lower heat of absorption, larger CO 2 capacity, and enhanced stability. 8,12 DMSO, as a highly polar organic solvent, has lower volatility and specific heat capacity than water. 13 In addition, it also has relatively low viscosity.…”

“…However, high energy consumption for solvent regeneration in the capture process prevents its large-scale implementation . Water-lean amine absorbents by partially replacing water with organic solvent have been proved to be a promising solution for energy-efficient CO 2 capture. , Recently, there has been a large number of studies on absorbent formulation and its CO 2 capture performance in this area. − In comparison to MEA, secondary alkanolamines, 2-(methylamino)­ethanol (MAE), with a methyl group connected to a N atom show comparative reaction kinetics, lower heat of absorption, larger CO 2 capacity, and enhanced stability. , DMSO, as a highly polar organic solvent, has lower volatility and specific heat capacity than water . In addition, it also has relatively low viscosity.…”

“…In addition, it also has relatively low viscosity. The use of water-lean blends is desirable to improve the CO 2 capture performance of aqueous and nonaqueous absorbents mentioned above. ,− We have no wish to defend the viability of the MAE + DMSO + water system as a candidate for industrial CO 2 absorbent. However, the literature about the physical properties of these blends is extremely scarce.…”