Low-Energy-Consumption CO₂ Capture by Liquid–Solid Phase Change Absorption Using Water-Lean Blends of Amino Acid Salts and 2-Alkoxyethanols

Abstract

Solvent regeneration for the conventional aqueous amine-based CO2 capture is very energy intensive. Development of phase-changing absorbents is an attractive solution for low energy consumption. In this work, a novel water-lean amino acid salt-based biphasic absorbent was proposed to improve CO2 capture performance and energy efficiency. Potassium prolinate (ProK) and potassium sarcosinate (SarK) with a secondary amino group were used as active components, and 2-alkoxyethanols with low volatility, low specific heat, and low viscosity were used as physical antisolvents and triggered the formation of solid phase during CO2 absorption. CO2 absorption and desorption characteristics in these systems and continuous capture cycles were investigated under ambient pressure. Relative regeneration energy consumption for solvent regeneration was also evaluated in comparison with the benchmark aqueous MEA. Phase change behavior and partition of CO2 absorbed in liquid and solid phases were characterized, and the product species in CO2-rich solid phase were identified by 13C NMR and XRD. Results demonstrated that using weak polar solvents, such as 2-methoxyethanol (EGME) and 2-ethoxyethanol (EGEE), can be favorable for the formation of solid precipitates in these systems investigated. Solid slurry with CO2 loading of 2.5–3.5 mol kg–1 can captured about 50–80% of the absorbed CO2. Ionic products such as bicarbonate and protonated amino acid salt were proved to be the main compositions in the solid precipitate. In comparison with aqueous 5.0 M MEA, the 3.0 M ProK/EGME system showed comparable cyclic capacity (about 0.80 mol kg–1) and a little higher desorption efficiency. Surprisingly, about 40–50% reduction of regeneration energy indicates that water-lean phase change ProK/EGME absorbent has a great potential for advanced CO2 capture technology.

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

“…Electronic analytical balances (OHAUS, CP214, Scout SE 1501F) were used for mass measurements. N 2 (99.99%, v/v), CO 2 (99.99%, v/v), and a standard gas (20.00 ± 0.02% CO 2 balanced with N 2 ) were purchased from the Shijiazhuang Xisanjiao oxygen generation station and used for calibration of two nondispersive infrared CO 2 analyzers (GXH-3011N, 0–20%; SKS-BA-CO 2 , 0–100%; uncertainty 1.0% FS) …”

Liquid amine–solid carbamic acid phase-separation system for direct capture of CO2 from air

“…Custelcean et al recently developed DAC system using amino acid potassium solution followed by the reaction with guanidine compound resulting in crystallization of insoluble carbonate salt. 20,21 These systems could remove CO2 from air, but the system requires sequential CO2 transfer system. Further research is therefore required to develop a versatile and simple solid-liquid separation system that are suitable for ambient CO2 absorption and that lead efficient CO2 desorption at low temperatures.…”

“…To satisfy these demands, a number of solid amine-based sorbents [13][14][15][16][17][18][19] and CO2absorption systems that utilize phase separation [20][21][22][23][24][25][26][27] have been developed. The ability of homogeneous liquid-phase systems to absorb CO2 has been improved by modifying the structures of the amine sorbents.…”

“…In the DAC system using amino acid potassium and guanidine, the CO2 absorption rate was reported to be ca 95 mmol h −1 for 1 mol amine. 20,21 The DAC system using alkaline base solution has been established in a plant-level operation with higher than the CO2 desorption temperature of the present system (333 K). Those results suggest that IPDA, which absorbs CO2 with sufficient rapidity (CO2 absorption rate: 214 mmol h −1 for 1 mol amine, SV: 6000 h −1 , Supplementary Fig.…”

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

“…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.…”