The blending of primary amines, with fast reaction kinetic, together with tertiary amines, with a large loading capacity, is an increasingly popular approach to develop high-performance CO 2 capture sorbents with low energy requirements for regeneration. In this study, we investigated the CO 2 absorption performance of several aqueous solutions obtained by mixing ethanolamine (MEA) and diethylethanolamine (DEEA) and compared them with that of individual MEA and DEEA. CO 2 loadings at equilibrium were measured experimentally under a wide range of operating conditions, at temperatures between 298 and 323 K, CO 2 partial pressures in the range 5–60 kPa, and different amine mixing ratios. In addition, 13 C NMR spectroscopy was employed to elucidate the reaction mechanisms and identify the species formed during CO 2 capture. The results of the study reveal the intricate interplay of MEA and DEEA in CO 2 capture, where MEA carbamate formation predominates in the early stages, gradually shifting to bicarbonate formation as the amine concentration decreases. Moreover, excess properties, which reflect non-ideal behaviors in amine blends, were introduced as a key parameter in the study. An excess property model, based on excess CO 2 loading, was developed to accurately predict the CO 2 equilibrium solubility without constant experimental measurement. As a result, good agreement was found between the experimental data and those calculated with the model (excess CO 2 loading) under the same operating conditions, with a average relative deviation of 1.1%.
Shuting Wang,Xueli Zhou,Qingyuan Song,Yuhuan Chen,Fang Yang
In this work, the densities of CO2-loaded and unloaded alkanolamine (1) + N, N-dimethylacetamide (DMAC) (2) mixtures were determined at temperature of (288.15 to 323.15) K and 101 kPa. The alkanolamines were primary amines, 3-amino-1-propanol (3A1P) and 1-amino-2-propanol (1A2P), and tertiary amine, 3-dimethylamino-1-propanol (3DMA1P). There CO2-unloaded 3A1P/1A2P/3DMA1P + DMAC binary systems with the whole concentration and two CO2-loaded 3A1P/1A2P + DMAC systems with alkanolamine mass fraction of (0.2, 0.3 and 0.4) were investigated. Based on the density values of CO2-unloaded binary systems, the thermal expansion coefficient (αp), excess molar volume (VmE), and apparent molar volume (Vφ,i) were calculated and discussed in terms of intermolecular interactions and spatial structure. The VmE values were positive under the studied conditions and increased with the temperature, and the maximum followed the decreasing order of 1A2P + DMAC > 3DMA1P + DMAC > 3A1P + DMAC. Additionally, the VmE data were well fitted with the Redlich-Kister equation with a small standard deviation (σ ≤ 0.024). For the CO2-loaded systems, the density values were correlated with temperature and concentration using different empirical equations, and the average relative deviations (ARD%) were less than 0.299%.
The removal of trace carbon dioxide (CO 2 ) from acetylene (C 2 H 2 ) through adsorption poses a significant challenge due to their similar kinetic diameters and physical properties. Here, we report a novel solid amine adsorbent, polyethyleneimine-diethanolamine functionalized silica dioxide (termed P/D-SD), which exhibited a remarkable CO 2 adsorption capacity of 1.76 mmol/g at 298 K and 0.0004 bar. The IAST selectivity of the CO 2 /C 2 H 2 (1/99, v/v) mixture of P/D-SD was 7.98E + 05. The exceptional separation performance of P/D-SD is demonstrated through breakthrough experiments, producing ultra-high purity C 2 H 2 (greater than 99.9 %) from CO 2 /C 2 H 2 (1/99) mixtures. Its CO 2 adsorption performance remains largely unaffected under different humidity condition. Furthermore, P/D-SD exhibited excellent stability in the adsorption–desorption cycle and rapid CO 2 adsorption kinetics at different temperatures when compared with P-SD. The adsorption mechanism of P/D-SD with CO 2 was studied as a chemisorption process via in situ DRIFTS.
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