Ethylamino Ethanol Research Articles

CO2 capture performance of AMP-EAE amine blends: Absorption in the microchannel and desorption from saturated solutions

Blended organic amine solutions are considered an effective strategy for developing highly efficient and low energy-consuming absorbents due to the possibility of combining the advantages of single amine. The 2-amino-2-methyl-1-propanol (AMP) and 2-(ethylamino)ethanol (EAE) amine blends were prepared in three molar ratios: blend-1 (nAMP:nEAE = 3:1), blend-2 (nAMP:nEAE = 1:1), and blend-3 (nAMP:nEAE = 1:3). The impacts of gas-liquid flow rate, amine concentration, molar ratio, temperature, and CO2 concentration on absorption performance were investigated using the serpentine microchannel. Additionally, the effects of amine concentration and molar ratio on the desorption performance of saturated solutions were also explored. The performance of amine blends in absorption and desorption was evaluated by measuring absorption rate, efficiency, and loading, as well as desorption efficiency, energy consumption, cycle capacity, and average desorption rate. The desorption results were compared to those of the benchmark solvent, 30 wt% MEA, under identical operating conditions. The results indicate that the 25 wt% blend-2 solution performs exceptionally well, exhibiting a 15 % increase in absorption efficiency compared to the AMP aqueous solution at a gas-liquid ratio of 20. Additionally, the cycle capacity and average desorption rate are 1.7 times higher than those of the 30 wt% MEA solution. Notably, the energy consumption of the 25 wt% blend-2 solution for desorption is only 60 % of the 30 wt% MEA solution.

Mass transfer and kinetic measurement and modeling for CO2 absorption into aqueous EAE and water-lean EAE/NMP solvents

Chemical absorption using amine solvent is currently available technology for CO2 capture from post-combustion flue gas. It is hindered by high operating cost and high capital cost due to high regeneration energy and slow CO2 absorption rate of amine solvent. Water-lean solvent of 2-(ethylamino) ethanol (EAE)/1-methyl-2-pyrrolidinone (NMP)/water could be a potential solution as it achieved significantly low regeneration energy of 2.3 GJ/tCO2 tested in a pilot plant. However, kinetics of CO2 reaction with EAE and mass transfer rate of CO2 absorption into EAE/NMP solvent are not fully understood. In this work, kinetics of CO2 absorption into unloaded aqueous EAE in 1–5 mol/L at 300–313 K and mass transfer of CO2 absorption into CO2-loaded EAE/NMP water-lean solvent in 5 mol/L with equilibrium CO2 partial pressure (PCO2*) range of 0.3–7 kPa at 312 K were studied in a wetted wall column. Kinetic data of aqueous EAE is interpreted by zwitterion mechanism, and the reaction is of first order with respect to EAE concentration in 1–5 mol/L at 300–313 K. CO2 absorption rate (kg’) of EAE/NMP water-lean solvent is 1.3–2.1 times greater than aqueous EAE due to the greater CO2 physical solubility. At lean and rich loading conditions, 5 M EAE in 3NMP/1water and 9NMP/1water show 2–7 times faster kg’ than 30 % MEA, and 1.4–2.5 times faster kg’ than 30 % PZ. It is found that EAE activity coefficient may increase in the presence of NMP in the solvent, and the estimated EAE activity coefficient in 1NMP/1water, 3NMP/1water, and 9NMP/1water are 2.13, 3.50, and 4.72, respectively. CO2 capacity of EAE/NMP solvent is 2–3.7 times greater than 30 % MEA and 1.2–2 times greater than 30 % PZ.

Kinetic study on CO2 absorption by aqueous secondary amine + tertiary amine blends: Kinetic model and effect of the chain length of tertiary amine

To study the reaction kinetic of CO2 absorption in aqueous secondary amine + tertiary amine blends, 1-Diethylamino-2-propanol (DEA2P) and 1-Dimethylamino-2-propanol (DMA2P) were selected to form aqueous amine blended solutions with 2-(Ethylamino) ethanol (EAE), respectively. The reaction kinetics of CO2 absorption in aqueous EAE/DEA2P solutions and EAE/DMA2P solutions were explored using the stopped-flow apparatus, and the reaction mechanism was then explored by Density Functional Theory (DFT) calculations. Based on the zwitterion mechanism and the base-catalyzed hydration mechanism, experimental reaction kinetics models were established. It was found that in secondary amine + tertiary amine blends, tertiary amines played the key role of the proton acceptor in step of zwitterion deprotonation. With the increase of the chain length of tertiary amine, the CO2 absorption rate increased. Through analysis, it was found that the main reason for the increased CO2 absorption rate was the presence of H-bond or the stronger proton affinity of N atom.

Comprehensive kinetic study of carbon dioxide absorption in blended tertiary/secondary amine solutions: Experiments and simulations

This study investigated the kinetics of CO2 absorption by aqueous solutions of 2-(ethylamino)ethanol (EAE) and 2-(butylamino)ethanol (BAE) using a stopped-flow device under varying concentrations of amine (0.02 ∼ 0.05kmol/m3) and temperature (293 K to 313 K), and also explored the kinetic behavior of N,N-diethylethanolamine (DEEA) when combined with EAE and BAE. The model involving a combination of the zwitterion mechanism and base catalysis mechanism was proposed with the better prediction of the reactions than other models. The AARD% for the two blended systems was 7.52 % and 7.95 %, respectively. The absorption mechanism and free energy barrier of blended amine aqueous solution were calculated and validated by Density Functional Theory (DFT) calculations. The reaction mechanism obtained from the calculation results is in good agreement with the kinetic model used in the experiment. This study highlights that consistency of model and simulation results and revealed the interaction effects of the blended amines. The effect of secondary amine chain length on absorption was also discussed, which gave the good significance to the further investigations and developments of blended CO2 solvents.

Equilibrium absorption of CO2 in aqueous solution of N-dimethylamino ethanol and 2-(ethylamino)ethanol, measuring and thermodynamic modeling

The equilibrium carbon dioxide solubility in aqueous solutions of N-dimethylaminoethanol (DMAE) 40 wt% + 2-(ethylamino) ethanol (EAE) 5 wt% and DMAE 30 wt% + EAE 5 wt% was measured at various temperatures (313.15, 328.15, 343.15, 358.15 K) in the range of pressures from 6.5 to 236 kPa. The enthalpy of absorption of carbon dioxide was measured for the mixture of DMAE (40 wt%) + EAE (5 wt%), at 328.15 K. The Deshmukh-Mather model was used to correlate the equilibrium solubility of carbon dioxide data, and the model parameters were optimized. The optimized model could correlate the vapor-liquid equilibrium with the 9.4 average absolute percentage deviation (AAD%), and the obtained AAD% for enthalpy of absorption in aqueous solution of DMAE (40 wt%) + EAE (5 wt%) was 24.0.

Bench-scale CO2 capture using water-lean solvent of 2-(ethylamino) ethanol, 1-methyl-2-pyrrolidinone, and water

Water-lean amine are promising solvent for CO2 capture to significantly reduce regeneration energy. However, existing water-lean solvent hasn’t been put into commercial application due to high reaction heat, slow CO2 absorption rate, and high amine volatility of amine. In this paper, amines with one secondary amino (—NH), one hydroxyl (—OH), and carbon chain length between 3 and 6 (C3-C6) in structure were preferred for water-lean solvent in the light of amine structure–activity relationship. 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water were favorable water-lean solvent for CO2 capture, and EMEA/NMP was tested in a bench-scale platform. EMEA/NMP solvents have equivalent CO2 removal efficiencies, and 40–69% lower regeneration energy compared to blended amines and MEA solvents. The lower regeneration energy of EMEA/NMP results from lower water vapor ratio, lower reaction heat, and lower heat capacity. Viscosity of EMEA/NMP at rich loading is 6.92–11.11 mPa·s at 40℃. Increased stripper temperature increases CO2 removal efficiency by decreasing lean loading in EMEA/NMP solvents. CO2 desorption dominates mass transfer in stripper at low temperature while water evaporation dominates at high temperature. The lowest regeneration energy obtained with 5.0 M EMEA/NMP at liquid/gas ratio of 10.5 L/m3 and stripper temperature of 80℃ was 0.99 kWh/kg CO2 (equivalent to 3.6 GJ/tCO2), which is 69% lower than that of 5 M MEA. EMEA/NMP has an increasing amine emission from 109 to 1891 mg/m3 as absorber temperature increases from 34℃ to 54℃. Advanced processes would be employed for volatile amine emission control in future study.

Energy-efficient carbon dioxide capture using piperazine (PZ) activated EMEA+DEEA water lean solvent: Performance and mechanism

Water vapor contained in industrial waste gas will be accumulated in non-aqueous amine solvents when used for CO2 capture and subsequently affect capture efficiency. While Piperazine (PZ) could be considered as an activator of the solution. Hence the effect of different contents of water and PZ added into the non-aqueous amine solvents on the CO2 capture performance has been investigated. 13C NMR has been used to identify the compounds present in aqueous CO2-rich amine solvents to characterize the mechanism of reactions. The energy consumption using 2-(ethylamino)ethanol (EMEA) water-lean amine solvent and aqueous monoethanolamine (MEA) solution was tested and compared on lab-scale, and further a comprehensive evaluation in a bench-scale pilot plant has been performed; It was found that the regeneration efficiency of the solution was reduced by approximately 10% when the water content was 10 wt%. The addition of PZ can recover the regeneration efficiency of the solvent to 94.2%. And its energy consumption was reduced by about 45% compared to the aqueous MEA solution in a 72-hour continuous absorption-desorption experiment. The results demonstrated that the aqueous PZ solution could improve the regeneration efficiency by involving in the proton transfer process. This work has proven that the blend of water-lean amine solvent and PZ is a novel, energy-efficient absorbent for CO2 capture.

Pilot test of water-lean solvent of 2-(ethylamino) ethanol, 1-methyl-2-pyrrolidinone, and water for post-combustion CO2 capture

Water-lean solvent for post-combustion CO2 capture is promising to significantly reduce regeneration energy. It hasn’t been put into commercial application due to unsolved challenges including water balance issue, increased viscosity, and high volatility. Even though numerous water-lean solvents were developed in laboratory, rare of them were tested in pilot scale. Water-lean solvent of 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water was tested in a CO2 capture pilot with flue gas rate of 280 m3/h. Effects of liquid/gas ratio and reboiler steam rate on CO2 removal efficiency, regeneration energy, lean/rich heat exchanger performance, and volatile amine emission were investigated. Water-lean EMEA achieved CO2 removal efficiency greater than 90 % and the lowest regeneration energy of 2.3 GJ/tCO2, which is 43 % lower than that of 5 M MEA. Water-lean EMEA showed significantly reduced latent heat, greater CO2 capacity, and lower reaction heat (secondary amino) than aqueous MEA and amine blends. It was found that water-lean EMEA regeneration in stripper had extremely lower lean loading (0.1–0.5 mol CO2/L) than aqueous MEA and amine blends, which enables a faster CO2 absorption rate in absorber and a greater CO2 capacity, but also causes larger volatile amine emission. Volatile amine emission after water wash was 110–380 mg/m3. 13C NMR spectrum suggested amine carbamate dominated CO2 absorption products. Due to that increased viscosity decreases heat transfer coefficient (h), lean/rich heat exchanger temperature difference (ΔT) for water-lean EMEA (6.5–7.5℃) was greater than MEA (3.5-5℃) and amine blends (5-6℃), yet smaller than biphasic solvent (8-9℃). A negative power (-0.614) function relation between h and viscosity was fitted and can be further used to normalize sensible heat.

An experimental and theoretical study on the effects of amine chain length on CO2 absorption performance

AbstractTo explore the effect of amine chain length on CO2 absorption performance, the reaction kinetics of CO2 absorption in aqueous 1‐dimethylamino‐2‐propanol (DMA2P), 1‐diethylamino‐2‐propanol (DEA2P), 2‐(methylamino)ethanol (MAE), and 2‐(ethylamino)ethanol (EAE) solutions with different concentrations were explored using the stopped‐flow apparatus. Additionally, Density Functional Theory (DFT) calculations were conducted to examine the reaction mechanism and the free energy barrier of the elementary reactions underlying CO2 absorption in these four aqueous amine solutions. Kinetic models for CO2 absorption in tertiary amines and secondary amines were established, based on the base‐catalyzed hydration mechanism and the zwitterion mechanism, respectively, both of which perform well in predicting the relationship between k0 and the amine concentration. The free energy barrier obtained by DFT is consistent with the activation energy barrier trend obtained by experiment. In addition, the effect of chain length on the free energy barrier was investigated through the chemical bond and weak interaction analysis.

Probing molecular interactions in the system {water + 2-(diethylamino) ethanol} using solvatochromic dyes and excess partial molar enthalpies, at 298.15 K

The polarity of the binary {water + 2-(diethylamino)ethanol (DEEA)} mixtures was investigated, across the whole composition range using solvatochromic dyes, expressed in terms of the Kamlet-Abboud-Taft (π*, α, β) and ETN Reichardt parameters, at 298.15 K. The preferential solvation model of Bosch and co-workers was applied to each solvatochromic dye. Direct excess partial molar enthalpies, HiE, for the same system, at the same temperature and atmospheric pressure, were obtained at both ends of the composition range using a semi-adiabatic isoperibol solution calorimeter and an expeditious method pioneered by Yoshikata Koga. Infinite dilution values of this same thermodynamic property were calculated for the DEEA in water and for the water in DEEA and compared with the literature values for the systems {water + 2-(dimethylamino)ethanol (DMAE)} and {water + 2-(ethylamino)ethanol (EEA)}, to infer the effect of branching and chain length on this property. Values for the interaction enthalpy between pairs of molecules of the same species, HiiE, were also estimated, in the same composition ranges studied, revealing endothermic processes, at both ends. A successful multiparametric correlation between excess partial molar enthalpy of DEEA and the solvent polarity parameters, π*, α and β allowed to quantitatively discriminate the relative relevance of the different types of the DEEA-solvent interactions.

Correlation comparison for prediction of density and viscosity of aqueous 2-(ethylamino)ethanol (EAE) for carbon capture

Aqueous amine solution for carbon dioxide (CO2) removal from absorption technology such as aqueous 2-(ethylamino)ethanol (EAE), is the effective technology to capture CO2 from gas stream. Also, the density and viscosity are the important properties for the design of absorption system. The correlations to predict these properties are developed. The objectives of this work are to apply the existing correlations and to examine the correlation comparison such as the Redlich–Kister equation, Wilson model and empirical polynomial correlation to predict these properties. The measured results of viscosity and density come from the previous study. The measurement data are used to determine the excess molar volumes and viscosity deviations, which are then correlated as a function of the mass fraction and temperature by using non-linear regression method. The temperature and concentration of this study are ranging from 293.15 to 323.15 K and 0.05 – 0.30 mass fraction, respectively. The results of this work show that, among these three correlations, the Redlich–Kister equation is the most appropriate model that best corresponded with the experimental results because it can provide the lowest average absolute deviation compared with the experimental results. This model yields percent deviations of 0.054 % for density and 0.350 % for viscosity. This model can be used to predict these properties for the range of working conditions.

Carbon dioxide adsorption/desorption performance of single- and blended-amines-impregnated MCM-41 mesoporous silica in post-combustion carbon capture

Abstract High-surface-area, hexagonal-structured mesoporous silica, MCM-41, was synthesized and wet impregnated with three different amines of 2-(ethylamino) ethanol (EAE), ethylenediamine (EDA), and tetraethylenepentamine (TEPA) for use as solid adsorbents in post-combustion CO2 capture application. The CO2 adsorption test was performed at 25°C and atmospheric pressure using 15/85 vol% of CO2/N2 at a 20-mL/minute flow rate. Desorption was carried out at 100°C under 20 mL/minute of N2 flow. The results show that the capacity and rate of CO2 adsorption obtained from all the amine-modified adsorbents were significantly increased with increasing amine loading due to carbamate formation. Desorption efficiency and heat duty for regeneration were also affected by the amount of amine loading. The more stable the carbamate produced, the higher the energy was required. They exhibited the highest adsorption–desorption performance at 60 wt% amines used for impregnation. Blended EAE/TEPA at different weight ratios at a total concentration at 60 wt% amines was impregnated on MCM-41 adsorbent. Sorbent impregnated with 50%/10% of EAE/TEPA showed the best performance of 4.25 mmolCO2/g at a high adsorption rate, a low heat duty of 12 kJ/mmolCO2 and with 9.4% reduction of regeneration efficiency after five repeated adsorption–desorption cycles.

Modeling of phase separation solvent for CO2 capture using COSMO-SAC model

BackgroundPhase separation solvents are proposed to replace conventional solvents for CO2 capture due to a significant reduction of absorbent regeneration heat. A predictive approach based on COSMO-SAC is developed to model the CO2 capture process using the phase separation solvent of 2-(ethylamino)ethanol (EAE) + water + diethylene glycol diethyl ether (DEGDEE). MethodsIn this approach, liquid phase compositions, including CO2 solubility, are determined from vapor-liquid-liquid equilibrium calculation with a chemisorption reaction in both liquid phases. The behavior of phase separation after CO2 capture and CO2 solubility in both CO2-lean and CO2-rich phases at 313 and 353 K can be well described by the proposed approach. Significant findingsThe overall root-mean-square-deviation (RMSD) in predicting compositions (128 data points) of all components in both liquid phases is 0.064, which is slightly better than a previous study on the accuracy of COSMO-SAC in LLE prediction (RMSD = 0.105). The phase separation behavior of solvent can be realized with the hydrophilic product upon CO2 absorption from the σ-profile analysis. The proposed framework is expected to be a useful tool for the development of a new phase separation solvent.

Combined experimental and computational study on the promising monoethanolamine + 2-(ethylamino)ethanol + sulfolane biphasic aqueous solution for CO2 absorption

To reduce the regeneration energy consumption for CO2 capture, an advanced monoethanolamine (MEA) + 2-(ethylamino)ethanol (EAE) + sulfolane biphasic aqueous solution was developed, and the phase separation mechanism was explored. The effects of the concentration ratio on the phase separation behavior, CO2 absorption performance, CO2 loading at the phase separation point, and CO2 desorption performance of MEA + EAE + sulfolane solutions were investigated comprehensively in experiments. The 3 M MEA + 2 M EAE + 5 M sulfolane showed the best properties with a large CO2 loading of 0.32 mol/mol at the phase separation point and the relative low regeneration energy consumption, which is comparable to 5 M MEA in absorption with an improved desorption performance. The molecular mechanism of phase separation was revealed by molecular dynamics simulations, illustrating that strong hydrogen bonding between amine products and water and enhanced intermolecular interaction among amine products, would promote an aggregation of amine products. This study provides a promising candidate for energy-efficient CO2 capture with molecular insights into a liquid–liquid phase separation.

New method of kinetic modeling for CO2 absorption into blended amine systems: A case of MEA/EAE/3DEA1P trisolvent blends

AbstractIn order to establish an accurate kinetic model for the aqueous amine blends, monoethanolamine (MEA), 2‐(ethylamino) ethanol (EAE), and 3‐(diethylamino)‐1‐propanol (3DEA1P) have been chosen as a typical CO2 absorption trisolvents. The reaction kinetics of aqueous amine blends with carbon dioxide have been investigated first combining experiments and molecular simulations. The stopped‐flow technology has been used to obtain the observed reaction rate constant of the overall reactions over the temperature range of 293 to 313 K and at different amine concentrations. A theoretical kinetic model, based on the first‐principles quantum‐mechanical simulations, has been put forward to interpret the reactions between CO2 and the aqueous trisolvent amine blends systems. The proposed model, based on the zwitterion mechanism and the base‐catalyzed mechanism, shows good prediction with an acceptable absolute average deviation (AAD) of 6.32%, and has been found to be satisfactory in determining the kinetics of the involved complicated reactions.

Unveiling the mechanism of CO2-driven phase change in amine + water + glycol ether ternary mixture

BackgroundPhase separation solvents have been developed for CO2 capture with the advantage of low regeneration energy. Understanding the mechanism of phase change driven by CO2 capture is critical toward design of phase separation solvents. MethodsIn this work, the molecular information of σ-profile and simulated ternary liquid–liquid equilibrium (LLE) phase diagram obtained from a predictive modeling based on COSMO-SAC method is used to investigate the phase behavior of phase separation solvents before and after CO2 absorption. Significant findingsTernary mixtures of three selected amines [2-aminoethanol (MEA), 2-(ethylamino)ethanol (EAE), 2-(butylamino)ethanol (BAE)] + water + glycol ether, with different strengths of hydrophilicity of amines, exhibit three types of partially miscible behaviors. Upon absorption of CO2, amine reacts to form hydrophilic reaction products (carbamate + protonated amine), resulting in the change of the molecular interactions and immiscible behaviors. Our study shows that amines, such as EAE, having a balanced interaction with water and glycol ether (exhibiting small immiscible region) are potential candidates for amine + water + glycol ether based phase separation solvent for CO2 capture.

Viscosity, density, and derived thermodynamic properties of aqueous 2-(ethylamino)ethanol (EAE), aqueous aminoethylethanolamine (AEEA), and its mixture for post-combustion CO2 capture

In the present study, viscosity and density of aqueous 2-(ethylamino)ethanol (EAE), aqueous aminoethylethanolamine (AEEA), and aqueous EAE + AEEA blend were measured in the temperature range of 293.15 K to 333.15 K at atmospheric pressure. Concentration of aqueous amines was used upto 30 wt% that is usually applicable for CO2 absorption from flue gases in post combustion CO2 capture process. EAE/AEEA weight ratio was 9/1, 8/2, and 7/3 in the aqueous EAE + AEEA blend. Viscosity of all mixtures increased by increasing amine concentration and decreased by increasing temperature of samples. Experimental viscosity data were correlated to newly proposed models and average absolute deviation (AAD) % was 1.515, 2.027, and 2.889 for viscosity of EAE + H2O, AEEA + H2O, and EAE + AEEA + H2O, respectively. Density of aqueous EAE and aqueous EAE + AEEA blend (at fixed EAE/AEEA weight ratio) decreased by increasing amount of amine in the mixture but aqueous AEEA showed increased density by increasing concentration of AEEA. Excess molar volume (VE) calculated for all aqueous mixtures and VE of aqueous EAE and aqueous AEEA was fitted in Redlich-Kister equation. Density of aqueous EAE + AEEA blend was correlated to a new empirical model and AAD % for this model was 0.018. Isobaric thermal expansion coefficient (αp) of binary and ternary solutions was calculated from density versus temperature data. Activation molar enthalpy (∆H∗), activation molar entropy (∆S∗), and activation molar Gibbs free energy (∆G∗) at 298.15 K for aqueous EAE, aqueous AEEA, and aqueous EAE + AEEA blend were calculated using viscosity and density data on the basis of Eyring theory of liquid viscosity.

Experimental data and modeling for density and viscosity of carbon dioxide (CO2)-loaded and -unloaded aqueous blend of 2-(ethylamino)ethanol (EAE) and aminoethylethanolamine (AEEA) for post-combustion CO2 capture

Amine based chemical absorption is the most developed technique for post-combustion CO2 capture from flue gases of low CO2 partial pressure. Density and viscosity data of CO2 – loaded and –unloaded absorbent are important in kinetics study and design the absorption column. Density and viscosity of CO2 loaded and –unloaded aqueous blend of 2-(ethylamino)ethanol (EAE) + aminoethylethanolamine (AEEA) were obtained experimentally in the temperature range of 293.15 to 323.15 K with 5 K temperature interval at atmospheric pressure. Concentration of aqueous EAE + AEEA blend was 10 wt%, 20 wt%, and 30 wt% with 7/3 weight ratio of EAE/AEEA. Excess volume was calculated by using experimental density data and correlated with Redlich-Kister type equation. Correlations were developed to calculate density and viscosity. For CO2-loaded and –unloaded aqueous EAE + AEEA blend, correlations predicted data were with average absolute deviation percentage (AAD %) of 0.1286, 0.0208, respectively for density while with AAD % 4.744, 4.433, respectively for viscosity. Wieland model was also correlated to CO2-loaded viscosity data and AAD % was 2.852 for this model. Moreover, diffusivity of CO2 into the aqueous EAE + AEEA blend was calculated using modified Stokes-Einstein equation.

Direct CO2 air capture with aqueous 2-(ethylamino)ethanol and 2-(2-aminoethoxy)ethanol: 13C NMR speciation of the absorbed solutions and study of the sorbent regeneration improved by a transition metal oxide catalyst

The removal of CO2 from the atmosphere (DAC technology) has been accomplished at room temperature and pressure with aqueous solutions of 2-(ethylamino)ethanol (EMEA) and 2-(2-aminoethoxy)ethanol (DGA). The absorption efficiency of the sorbents has been investigated in five cycling steps of absorption-desorption, and the speciation of the solutions has been studied by 13C NMR analysis. The CO2 capture efficiency of both fresh amines is about 88%, and that of the regenerated EMEA solutions decreases to about 79% once the equilibrium between amine regeneration (at 110 °C) and CO2-loaded amine has been reached. Instead, the efficiency of regenerated DGA progressively decreases to 69% at the end of the fifth cycle. 13C NMR analysis of the absorbed solutions of EMEA indicates that CO2 is captured as amine carbamate and bicarbonate (nearly 1:1 proportion), whereas DGA carbamate is the sole species of captured CO2. To improve the efficiency of regenerated DGA solutions, solid WO3 has been employed as desorption catalyst in five subsequent cycles of absorption and desorption. At equilibrium, the efficiency of CO2 capture increased to 85%, substantially greater than that of regenerated EMEA. The catalyst has been recovered unchanged at the end of each desorption step.

Thermodynamic modeling and new experimental CO2 solubility into aqueous EAE and AEEA blend, heat of absorption, cyclic absorption capacity and desorption study for post-combustion CO2 capture

In the present study, carbon dioxide (CO2) solubility into aqueous blend of 2-(ethylamino) ethanol (EAE) and aminoehtylethanolamine (AEEA) was measured. The performance of CO2 capture by this amine blend was investigated in terms of CO2 solubility, heat of absorption, cyclic CO2 solubility, and initial rate of change of CO2 solubility. CO2 absorption study was carried out using bubble column reactor in the temperature range of 298.15 to 323.15 K, 8.11 to 20.27 kPa CO2 partial pressure, 0.10 to 0.30 wt fraction of AEEA in EAE and AEEA blend, and 10 to 30 wt% total concentration of blend solution. Desorption experiments were performed at 393.15 K. Maximum CO2 solubility was 1.033 mol CO2/mol amine at 298.15 K, 20.27 kPa, 0.30 wt fraction of AEEA in the blend, and 10 wt% of EAE and AEEA solution. A semi-empirical Kent-Eisenberg thermodynamic model and an empirical model were developed to calculate equilibrium CO2 solubility in the studied range of operating conditions with 2.56% and 0.45% average absolute deviation, respectively. At 313.15 K, 15.20 kPa CO2 partial pressure and total concentration of 30 wt% of EAE and AEEA blend, the equilibrium CO2 solubility was resulted as 0.748 mol CO2/mol amine and cyclic solubility of 0.503 mol CO2/mol amine was achieved. Heat of CO2 absorption was measured based on Gibbs Helmholtz equation and found as −72.25 kJ/mol for 30 wt% aqueous EAE and AEEA blend. Results of absorption capacity of EAE and AEEA solution and monoethylethanolamine (MEA) were compared at same operating conditions. This blend had higher CO2 solubility, lesser heat of absorption, more cyclic capacity and faster rate of change of initial CO2 solubility than MEA.