Modified Kent Eisenberg Model Research Articles

CO2 solubility in aqueous solutions of blended amines: Experimental data for mixtures with MDEA, AMP and MPA and modeling with the modified Kent-Eisenberg model

CO2 solubility in aqueous solutions of blended amines: Experimental data for mixtures with MDEA, AMP and MPA and modeling with the modified Kent-Eisenberg model

CO2 solubility in aqueous N‐methylcyclohexylamine (MCA) and N‐cyclohexyl‐1,3‐propanediamine (CHAP) solutions

AbstractN‐methylcyclohexylamine (MCA) and N‐cyclohexyl‐1,3‐propanediamine (CHAP) have been suggested, in mixtures with lipophilic amines, as potential phase change solvents for CO2 capture applications, and subsequently studied as promising alternatives to monoethanolamine (MEA) for minimizing the desorber's energy requirements. In this study, new high pressure experimental data were obtained for the solubility of CO2 in aqueous solutions containing MCA or CHAP at 313 and 333 K. The obtained data were used to parameterize the modified Kent–Eisenberg model. In this direction, CHAP was modeled assuming a “principle of independent reactivity,” that is, that the reactivity of each amine group does not depend on the potential reaction of the other one. It was shown that through this approach the model can be successfully applied to diamines using the relevant equations of amine mixtures.

Experimental and Thermodynamic Investigation on CO2 Absorption in Aqueous MEA Solutions

The vapor-liquid equilibrium (VLE) of CO2 in a reactive solvent is essential for the proper simulation and design of CO2 absorption processes. This work presents a systematic investigation on CO2 absorption in various aqueous monoethanolamine (MEA) solutions. CO2 solubility in MEA was measured at 298, 313, 333, and 353 K with CO2 partial pressure ranging from 34.5 to 78.0 kPa. A modified Kent-Eisenberg model was developed based on the measured solubility data, showing good predictions over the liquid phase speciation for the CO2-H2O-MEA system. We presented a new analysis based on the first-order difference curve of distribution profiles of the species. Based on the main reactions that occurred, the CO2 absorption process was demonstrated to be divided into four regions with increasing CO2 loading from 0 to 1. Accordingly, kinetic study was proposed to be conducted in the first region, whereas measuring of mass transfer in the first three regions. The findings in this work extend the existing knowledge of CO2 absorption process in terms of speciation and can provide important guidance for further study of the process characteristics using aqueous amine absorbents.

CO2 solubility and thermophysical properties in aqueous mixtures of piperazine and diethanolamine

The population rise and economic development lead to increased energy utilization. This energy utilization is largely based on fossil fuel combustion and the industrial operations in oil and gas industry that result in CO2 emissions. The solvent mixtures of piperazine/diethanolamine (PZ/DEA) were examined to substitute for improved carbon dioxide (CO2) absorption from the natural gas stream. The CO2 solubility in the blends of the piperazine (PZ) and diethanolamine (DEA) was evaluated at 303.2, 323.2, and 343.2 K, and partial pressures of CO2 at (100–1000 kPa). The mixtures considered were DEA (20, 40 wt%), DEA (20 wt%) + PZ (5 wt%), DEA (20 wt%) + PZ (10 wt%), DEA (40 wt%) + PZ (5 wt%), and DEA (40 wt%) + PZ (10 wt%) aqueous solutions. The CO2 loadings (mole CO2/mole amine) into the solutions were described concerning the equilibrium partial pressures of CO2 at the considered temperatures. An increase in solubility of CO2 was achieved using aqueous PZ, showing prospects to be a desirable mixture with the DEA solvent for CO2 absorption. The experimental results showed reasonable correlations to the modified Kent-Eisenberg model. The refractive index and density data of the alkanolamine blends were determined as a feature of temperature, demonstrating the decrement in the thermophysical properties when the temperature of the mixtures was increased. These findings on CO2 solubility and thermophysical properties provide key insights into the screening and practical use of next-generation solvents for CO2 absorption.

Solubility of CO2 in nonaqueous system of 2-(butylamino)ethanol with 2-butoxyethanol: Experimental data and model representation

Nonaqueous amine-based system is an attractive solution to overcome high-energy-intensive CO2 capture process using the conventional aqueous amines. Advanced nonaqueous absorbent of 2-(butylamino)ethanol (BAE) with 2-butoxyethanol (2-BE) has been recently proposed for low-energy-consumption CO2 capture. In this work, Henry’s law constants of CO2 in the BAE/2-BE blend were obtained by N2O/CO2 analogy, and correlated in the temperature range of (283–333) K. Vapor-liquid equilibrium (VLE) data for the BAE + CO2 + 2-BE system at 65.4% (mass) BAE were also determined in a stirred equilibrium cell at temperatures of (313–393) K and CO2 partial pressures up to 275 kPa. A single apparent equilibrium constant KCO2,app was proposed for this system and correlated as a function of temperature, carbonated degree of amine and CO2 loading. Solubility data were well represented by the modified Kent-Eisenberg model with an average absolute relative deviation (AARD) of 13%.

Equilibrium CO2 solubility of novel tris(2-aminoethyl) amine as a promoter to N-methyldiethanolamine and 2-amino-2-methyl-1-propanol

• An innovative semi-automated stirred-cell apparatus developed for CO 2 absorption. • CO 2 solubility was examined in novel blends of aq. (TAEA + MDEA/AMP) • VLE data was correlated using Modified Kent-Eisenberg and ANN models. • Reaction scheme was analyzed using 13 C NMR and FTIR-ATR. • Speciation and pH of CO 2 absorbed solution were estimated. This study involves the experimental measurements and theoretical analysis of equilibrium CO 2 solubility in a novel activator (tris(2-aminoethyl) amine, TAEA) and its blend with commercial solvents like ( N -methyldiethanol amine, MDEA) and (2-amino-2-methyl-1-propanol, AMP). All the measurements have been conducted at a fixed total amine concentration of 3 M (M) by varying the promoter concentration to (0.1–0.7) in an interval of 0.2 M, and temperatures range from (293.15–323.15) K at different CO 2 partial pressures in the range of 2–500 kPa. The experimental data are modeled using a modified Kent-Eisenberg (KE) equilibrium model and feed forward neural network model. The equilibrium constants linked to TAEA deprotonation and carbamate formation reactions are regressed as a function of CO 2 partial pressure, amine concentration, and temperature to fit the equilibrium CO 2 solubility data using a modified KE model. To know the reaction scheme and recognize the various essential reaction products in the CO 2 -loaded solvents 13 C NMR and FTIR-ATR analysis have been performed.

Solubility of N2O and CO2 in nonaqueous blends of 2-(methylamino)ethanol and 2-methoxyethanol

Nonaqueous secondary alkanolamine-based systems, replacing conventional water with 2-alkoxyethanols as cosolvents, have recently attracted much attention for an energy-efficient CO2 capture process. In this work, physical solubility of N2O and CO2 in 2-(methylamino)ethanol (MAE), 2-methoxyethanol (2-ME) and their blends was measured and correlated at temperatures ranging from (283.2 to 333.2) K. Vapor-liquid equilibrium (VLE) data for the CO2 + MAE + 2-ME system at 7.8, 19.4 and 39.1 mass% MAE were also measured in a stirred equilibrium cell at temperatures of (313.2–393.2) K and CO2 partial pressures up to 270 kPa. VLE data were represented by a modified Kent-Eisenberg model with an AARD of 12.6%. The apparent equilibrium constants considering the liquid nonideality were well correlated as a function of temperature, concentration of carbamate product and CO2 loading.

Prediction of CO2 solubility in aqueous solutions of N, N-Diethyl ethanolamine (DEEA): A modified Kent-Eisenberg model approach

A tremendous increase in the carbon dioxide emissions over the last few decades has caused serious environmental concern. The research fraternity is working towards the discovery of novel solvents for carbon dioxide with greater removal efficiency. N, N-Diethyl ethanolamine (DEEA), a tertiary amine which can be prepared from renewable resources, is a potential absorbent for carbon dioxide removal. Determination of the equilibrium characteristics of the system plays a key role in the designing of industrial plants. In this work, the equilibrium solubility of CO2 in aqueous solutions of DEEA at different temperatures and CO2 partial pressures has been modeled using the modified Kent-Eisenberg model. The model predicted values were found to be in good agreement with the reported experimental data.

Investigation on the inclusion of 1-(2-aminoethyl) piperazine as a promoter on the equilibrium CO2 solubility of aqueous 2-amino-2-methyl-1-propanol

The present work demonstrates the experimental and theoretical study of equilibrium CO2 solubility in a potential absorbent, aqueous 1-(2-aminoethyl) piperazine (AEP) and its blend with 2-amino-2-methyl-2-propanol (AMP). The measurements have been conducted at 303.2 to 323.2 K and within the CO2 partial pressure range of 2 to 250 kPa. The experimental data are modeled using modified Kent-Eisenberg (KE) equilibrium model for all the concentration range. Carbamate hydrolysis and AEP deprotonation constants are expressed as a function of pressure, temperature and amine concentration from the modified KE model. The developed model is used to predict the equilibrium liquid phase speciation in the CO2 loaded amine solution. An artificial neural network (ANN) model is also developed to predict the CO2 solubility in the understudy solvent system. The feed forward ANN model provides very good prediction with respect to the experimental solubility data having an average absolute deviation (% AAD) of 0.16. Qualitative 13C NMR and FTIR-ATR analysis have been performed for CO2 loaded solvent to understand the reaction scheme and identify the various important reaction products. Further, physicochemical properties such as density and viscosity of both the binary and ternary solvent system were also determined and correlated using Redlich-Kister and Grunberg-Nissan models.

A comprehensive kinetic and thermodynamic study of CO2 absorption in blends of monoethanolamine and potassium lysinate: Experimental and modeling

In this work, a kinetic and thermodynamic study of CO2 absorption in blends of monoethanolamine (MEA) and potassium lysinate (K-Lys) solutions was carried out at low CO2 partial pressures and temperatures (303–323 K). The CO2 loading capacity, density and viscosity of MEA + K-Lys solutions were measured. A modified Kent-Eisenberg model was applied to predict the CO2 loading capacity and also to determine the reaction equilibrium constants for the MEA + K-Lys system. The results showed that the model predictions are in excellent agreement with the experimental data. In order to study the reaction kinetics between CO2 and the MEA + K-Lys solution, the values of the reaction rate constant, the overall reaction kinetic constant, reaction order, physical solubility and CO2 diffusivity were determined. Finally, the absorption performance of the MEA + K-Lys system was compared with other common CO2 absorbents in terms of absorption heat, CO2 loading capacity and absorption rate. It was found that MEA + K-Lys has a better performance compared to other absorbents which makes it an attractive alternative to alkanolamines for CO2 capture.

VLE of Carbon Dioxide-Loaded Aqueous Potassium Salt of L-Histidine Solutions as a Green Solvent for Carbon Dioxide Capture: Experimental Data and Modelling

In this study, vapour-liquid equilibrium of CO2-loaded aqueous potassium salt of L-histidine was studied for a wide range of temperature (313.15–353.15 K), pressure (150–4000 kPa), and solvent concentrations (1–2.5 molar). The experimental results show that L-histidine has an excellent absorptive capacity for carbon dioxide. When compared to conventional solvent (monoethanolamine) and amino acid salt (potassium L-lysinate) at similar process conditions, L-histidine has superior absorption capacity. Moreover, modified Kent–Eisenberg model was used to correlate the VLE of the studied system with excellent agreement between the model and experimental values. The model exhibited an AARE% of 7.87%, which shows that it can satisfactorily predict carbon dioxide solubilities in aqueous potassium salt of L-histidine at other process conditions. Being a biological component in origin, almost negligibly volatile, and highly resistant to oxidative degradation, L-histidine offers certain operational advantages over other solvents used and has a promising potential for carbon dioxide capture.

Equilibrium solubility and kinetics of CO2 absorption in hexamethylenediamine activated aqueous sodium glycinate solvent

Equilibrium solubility and absorption kinetics of CO2 in hexamethylenediamine (HMDA) activated aqueous sodium glycinate (SG) solvent are measured in the temperature range of 313–333 K. For the experimental investigation, HMDA concentration in the solvent is varied in the range of 5–15 mass% keeping total amine concentration at 30 mass%. Solubility data is presented in the form CO2 loading (mole CO2 absorbed per mole of total amine). Kinetics of CO2 absorption is evaluated assuming pseudo first order reaction condition. Both solubility and kinetics of CO2 absorption are found to enhance significantly due to addition of small amount of HMDA in the aqueous SG solvent. CO2 loading data is correlated using modified Kent-Eisenberg model. For developing kinetic model, overall rate is assumed to be the combined rate contribution of CO2-HMDA and CO2-SG reaction system. Based on this concept, a kinetic model is proposed using zwitterion mechanism for both the component reaction system. Kinetic and solubility models developed in this work are in good agreement with the experimental data with average absolute deviation of 7.4% and 4.5% respectively.

Experimental and Modeling Study of Vapor Liquid Equilibrium for a Methyldiethanolamine–CO2–H2S–Water Quaternary System Using Activity Coefficient Models with Corrected Equilibrium Constants

The solubilities of CO2 and H2S mixtures in methyldiethanolamine aqueous solutions were investigated in the wide temperature range from 313.15 (absorption range) to 403.15 K (stripping range) using the static method. The values of equilibrium constants for amine protonation (K1), activity coefficients (γi), and fugacity coefficients (Φi) were regressed from the newly obtained experimental solubility data to correct nonideality. In order to obtain the equilibrium constants for amine protonation, modified Kent–Eisenberg model was applied. Then, two kinds of activity coefficient models, the Deshmukh–Mather model and the electrolyte nonrandom two-liquid model, were applied to minimize the gaps between experimental data and predicted values with newly obtained equilibrium constants. In this study, six thermodynamic models were presented by combining (1) equilibrium model and (2) activity coefficient models. Based on the best fitted solubility results, the mole fractions of all electrolytes, the pH in the liqui...

Effects of piperazine concentration and operating conditions on the solubility of CO2 in AMP solution at low CO2 partial pressure

ABSTRACTIn this study, new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol and piperazine (PZ) are provided. The two famous Deshmukh–Mather and Kent Eisenberg thermodynamic models are utilized to predict the CO2 absorption. The experimental data show that the solubility of CO2 decreases as the temperature increases. Our data suggest that the addition of PZ has different effects on CO2 absorption under different partial pressure of the CO2 in the gas stream. For high partial pressure, the addition of PZ promotes the absorption performance. However, at low CO2 partial pressure, PZ addition results in less saturated CO2 loading. The Deshmukh–Mather model can provide an accurate prediction of the experimental data at high partial pressure of CO2 (i.e. AAD = 3.4%) whereas the modified Kent–Eisenberg model can capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure (i.e. AAD = 10%).

Application of aqueous blends of AMP and piperazine to the low CO2 partial pressure capturing: New experimental and theoretical analysis

In this study, a new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) were provided. The two famous Deshmukh-Mather and Kent Eisenberg thermodynamic models were utilized to predict the CO2 absorption. CO2 loading data in aqueous AMP + PZ were assessed over the different ranges of temperatures (293, 303, 313 and 323 K), CO2 partial pressures (18.13, 27.19 and 72.52 kPa) and solvent concentrations ((0.1, 0.2, 0.3 M PZ) + (1.5, 2, 3, 4 M AMP)) in local atmospheric pressure (90.66 kPa) on samples of flue gases from thermal and central power plants of Esfahan Steel Company. For high partial pressure of CO2 in feed gas stream, the addition of PZ promotes the absorption rate. However, at low CO2 partial pressure, PZ addition results in less CO2 loading. The Deshmukh-Mather model could provide an accurate prediction of the experimental data at high partial pressure of CO2 whereas the modified Kent-Eisenberg model could capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure. The Average Absolute Deviation percentage (AAD%) used to adjust the parameters of the models. The AAD was calculated 15.02% and 19.49% for the Deshmukh-Mather and Kent-Eisenberg models, respectively.

Characterizing CO2 capture with aqueous solutions of LysK and the mixture of MAPA + DEEA using soft computing methods

Accurate data in the field of CO2-capture using new high potential absorbents as alternatives to the traditional ones is of great interest within scientific and engineering communities. In this direction, two robust modeling strategies, viz. Stochastic Gradient Boosting (SGB) tree and Genetic Programming (GP) are used to 1) predict the solubility of CO2 in aqueous potassium lysinate (LysK) solutions as a function of temperature, partial pressure of CO2, and the mass fraction of LysK; and 2) predict the solubility of CO2 in the mixture of MAPA + DEEA aqueous solutions as a function of temperature, partial pressure of CO2, and the concentration of MAPA and DEEA based on previously published data. The efficiency and precision of the proposed models are checked graphically and statistically. Results show that both proposed models are competent in accurate and reliable predictions (R2 > 0.98 and RMSE < 0.06). However, the SGB models are superior to the GP models. Additionally, the proposed models are compared to the modified Kent-Eisenberg model for predicting the CO2 solubility in LysK solutions, and shown to have better outputs.

Thermodynamic modelling of carbon dioxide solubility in aqueous amino acid salt solutions and their blends with alkanolamines

In this study, two thermodynamic approaches, namely explicit model and modified Kent-Eisenberg model are presented for the accurate determination of carbon dioxide solubility in aqueous solutions of amino acid salts with different levels of complexity. Both models were further extended to the correlation of carbon dioxide solubility in aqueous blends of amino acid salts with alkanolamines. Firstly, the explicit model consists of a single mathematical equation. Its structure is computationally simple and derived from equilibrium thermodynamics theory. Secondly, the modified Kent-Eisenberg model utilizes detailed reaction mechanism for development of a polynomial equation, that is solved by combining all non-idealities in two correction factors. Both models suitably determined the thermodynamics of carbon dioxide loaded aqueous amino acid salt solutions and their blends with alkanolamines. The results were in good agreement with experimental data for representative amino acid salt solutions (potassium and/or sodium salts of lysine, glycine, proline, sarcosine, serine, threonine, alanine, phenylalanine, amino-butyric acid, glutamine and asparagine) and their blends with alkanolamines (2-amino-2-methyl-1-propanol and piperazine) for range of process parameters. For carbon dioxide solubility in aqueous amino acid salt solutions, the AARE% for explicit and modified Kent-Eisenberg model was 13.85% and 13.84%, respectively. For carbon dioxide solubility in aqueous blends of amino acid salt and alkanolamine solutions, the AARE% for explicit and modified Kent-Eisenberg model was 18.25% and 17.25%, respectively. Both models use a small number of adjustable parameters. This indicates that generated parameters are able to accurately predict the carbon dioxide solubility at other process conditions, with minimum computational intricacy.

Solubility of CO2 in aqueous sodium β-alaninate: Experimental study and modeling using Kent Eisenberg model

In this work, the equilibrium solubility of CO2 in aqueous solution of 10, 20, and 30wt% sodium β-alaninate (Na-βala) was investigated using high pressure solubility cell. The solubility experiments were carried out at temperatures 303.15, 313.15, and 333.15K and over CO2 partial pressure ranging from 2 to 25bar. Experimental results showed that with the increase in Na-βala concentration and temperature of the system, CO2 loading decreases. Whereas, the CO2 loading increases by increasing the partial pressure of CO2. Furthermore, a modified Kent–Eisenberg model was used to correlate CO2 solubility data as a function of temperature, concentration and CO2 partial pressure. An average absolute deviation of 12.8% was obtained between the experimental and model correlated data, which indicated the good correlation capability of the applied model.

An experimental and modeling study of CO2 solubility in a 2-amino-2-methyl-1-propanol (AMP) + N-methyl-2-pyrrolidone (NMP) solution

In this study, an experimental setup based on the static-synthetic method was used to measure the new experimental data of CO2 solubility in an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) + N-methyl-2-pyrrolidone (NMP) solution. For the static-synthetic method, the mass balance of compositions and the pressure–volume–temperature conditions were used for measuring the amount of absorbed CO2 by the AMP+NMP solution. The measurements were performed over a temperature range of 313.15–353.15 K, CO2 partial pressure up to 316.7 kPa, and in different concentrations of the AMP+NMP solution. Two models, modified Kent–Eisenberg, and Deshmukh–Mather, based on the empirical correlations and activity-fugacity approach, respectively, were used for the prediction of experimental data. The parameters of the equilibrium constants of the protonation and carbamate reactions for the modified Kent–Eisenberg model and the interaction parameters for Deshmukh–Mather model were obtained. For validation of our setup, a new set of experimental data for the solubility of CO2 in an aqueous solution of AMP, methyldiethanolamine (MDEA) and diethanolamine (DEA) were measured and compared with existing experimental data in the literature, and good results were obtained. The results of the modeling study showed that the Deshmukh–Mather model gave a better prediction of experimental CO2 loadings data than the modified Kent–Eisenberg. Also, the results showed that the solubility of CO2 in an aqueous solution of AMP+NMP increases as the CO2 partial pressure increases while the temperature decreases.

CO2 absorption using aqueous potassium lysinate solutions: Vapor – liquid equilibrium data and modelling

The solubility of CO2 in aqueous potassium lysinate (LysK) solutions was measured in a stirred reactor at temperatures from 298 to 353K, for 9.0, 17.4, 25.3, 33.1 and 41.2mass% LysK and CO2 partial pressures up to 110kPa. The vapor-liquid equilibrium (VLE) data were interpreted using the modified Kent-Eisenberg model. The apparent equilibrium constants of carbamate hydrolysis and amino acid deprotonation were correlated as a function of temperature, CO2 loading (expressed as mole CO2 per mole LysK) and LysK concentration to fit the experimental solubility data. The proposed model satisfactorily predicted the VLE data for the H2O-LysK-CO2 system, especially at moderate to high CO2 loading, with an average absolute deviation within 3.2%. Liquid species in the CO2-loaded LysK solutions were also qualitatively characterized by 13C NMR experiments.