Performance and Mechanisms of Triethylene Tetramine (TETA) and 2-Amino-2-methyl-1-propanol (AMP) in Aqueous and Nonaqueous Solutions for CO₂ Capture

Abstract

Nonaqueous amines are currently being explored for energy-efficient postcombustion CO2 capture, but the absorption capacity and regeneration efficiency of most absorbents still need to be further improved. In this work, a mixture of triethylene tetramine (TETA) and 2-amino-2-methyl-1-propanol (AMP) dissolved in ethanol was chosen as a nonaqueous absorbent for CO2 capture and performed with high absorption loading and regeneration efficiency. In addition, the changes of the components during the absorption–desorption process and reaction mechanisms of nonaqueous absorbents were explored by 13C NMR spectroscopy and compared with those of aqueous absorbents. The results showed that TETA/AMP/ethanol had higher absorption loading and regeneration efficiency (3.71 mol kg–1, 95.4%) after the fifth regeneration cycle than TETA/AMP/water (3.54 mol kg–1, 38.8%) when the amine mass concentration was 40 wt %. CO2 capture by TETA/AMP aqueous and nonaqueous solutions proceeded by two different mechanisms. Polycarbamate and alkyl carbonate of C2H5OCO2 – formed in the TETA/AMP/ethanol solution, while polycarbamates and HCO3 –/CO3 2– formed in the TETA/AMP/water solution. Moreover, the regeneration efficiency of the nonaqueous solution was higher than that of the aqueous solution because the reaction products were easily decomposed in ethanol, and the regeneration consumption of the organic solvent was lower than that of water.

NMR Techniques and Prediction Models for the Analysis of Species Formed in CO2 Capture Processes with Amine-Based Sorbents: A Critical Review

“…To further enhance the performance of the absorbents, binary non-aqueous organic amines were studied. Barzagli et al 13,91,99 The speciation during absorption process in TETA-AMP-ethanol system, investigated by Liu et al 72 using 13 C NMR, was similar to TETA-ethanol system, however both carbamates of TETACO 2 − and AMPCO 2 − and the alkyl carbonate, C 2 H 5 OCO 2 − , were not found after desorption.…”

“…Liu et al 72 applied 13 C NMR spectroscopy to track the spepciation in in aqueous triethylenetetramine (TETA) during the whole CO 2 capture process, including absorption and desorption. As a finding, during the absorption process the NMR peaks of carbamates were between 163.5 and 164.5 ppm, while CO 3 2− /HCO 3 − were at 160.3 ppm.…”

“…Alkyl carbonates in different organic diluents are quite unstable species that could be generated during the absorption, when CO 2 is in significant excess with respect to amine, as demonstrated also from a 13 C NMR spectroscopic study carried out by Barzagli et al 13 As C 2 H 5 OCO 2 − is an unstable species, it quickly disappears during the desorption process; meanwhile, amine carbamates decrease but still exist. 72 Solutions of AMP in triethylene glycol dimethyl ether (TEGDME) and in N-methyl-2-pyrrolidone (NMP)…”

Densities and Viscosities of Binary and Ternary Solutions of Triethylenetetramine, 2-Amino-2-methyl-1-propanol, and Water for Carbon Dioxide Capture

“…The validation of the experimental technique employed in this study is presented in Table , where the density and viscosity values of pure H 2 O, AMP, TETA, and binary solutions TETA + H 2 O and AMP + H 2 O from the literature are also compared with those obtained here (experimentally). Table also presents the deviation from literature, ,,− which is calculated by eq . where Y lit represents the viscosity and the density in the literature and Y exp is the experimentally obtained viscosity and density (this study). Furthermore, Table indicates the consistency between the values of density and viscosity in this study and in previous studies.…”

Density, Viscosity, and Excess Properties of Binary Mixtures of 2-(Methylamino)ethanol with 2-Methoxyethanol, 2-Ethoxyethanol, and 2-Butoxyethanol from 293.15 to 353.15 K

“…Accordingly, nonaqueous blends have recently been developed based on the replacement of water by organic solvents, with the purpose of maintaining good mass transfer performances yet partly avoiding their disadvantages. , Using organics as solvents can provide several advantages including lowering the energy consumption, corrosiveness, and degradation. These solvents include volatile alcohols (e.g., methanol, ethanol, and butanol), − low volatile alcohols and glycols (e.g., benzyl alcohol and glycols) or their mixtures, − glycol ethers, , dimethylformamide, and ionic liquids . Compared with water and other organics, 2-alkoxyethanols such as 2-methoxyethanol (EGME), 2-ethoxyethanol (EGEE), and 2-butoxyethanol (EGBE) have attractive properties such as low volatility, low specific heat capacity (about 2.2–2.4 kJ K –1 kg –1 ), and low enthalpy of vaporization .…”