Solubility Of CO2 In Solutions Research Articles

Thermodynamic modeling for ternary clathrate hydrates of carbon dioxide, nitrogen and tetrahydrofuran

Hydrate-based CO2 separation technology is one of research hotspots in the field of Carbon Capture, Utilization, and Storage. However, thermodynamics, such as phase temperature and pressure, are very important for CO2 separation. In this study, a thermodynamic model was developed for calculating the temperature, pressure, separation efficiency and separation factor of the CO2-N2-THF/H2O system at the three-phase equilibrium of vapor–liquid-hydrates (V-L-H). The Chen-guo model was applied for the hydrate phase and the Patel-Teja equation of state (EOS) was used for the vapor phase. The Wilson activity coefficient model was employed for the liquid phase and the solubility of CO2 in solution was calculated using Henry's law. The average absolute deviation of the equilibrium pressure and temperature compared to the experimental data are 10.441% and 0.343%, respectively, which showed that the predicted three-phase equilibrium pressure and temperature were in good agreement with the experimental results. The three-phase equilibrium temperature and pressure of CO2 and N2 gas mixture in pure water and in THF aqueous solutions were compared. The results showed that THF had a promotion effect in reducing temperature and pressure of CO2 hydrate formation.

Glucosamine for CO2 Capture: Absorption Kinetics, Promoted Absorption Rate, and Comparison with Other Amino Sugars

Amino sugars─sugars wherein the amine group substitutes the hydroxyl group─are renewable and ecofriendly CO2 separation solvents. In this work, the kinetics of CO2 absorption in the amino sugar glucosamine (GA) was studied. Absorption rates in aqueous GA solutions (0.1–1 M) were measured in a stirred cell reactor in the 303–313 K range. At T = 308 K, the value of the reaction rate constant for GA (0.1 M) was 27 M–1 s–1. The two-step zwitterion mechanism was employed for describing the reaction pathway. Some useful characteristics of GA solutions, such as density and viscosity, were measured. Using the modified Stokes law and the N2O analogy method, the diffusivity and solubility of CO2 in solutions were determined. The liquid-side mass-transfer coefficient was found to be 0.005 cm/s at 308 K. Three amine promoters were chosen to improve the reactivity of GA, viz., monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ). Mixtures of GA/PZ (2.5/0.5 M) were the most reactive. The reactivity of two further amino sugars, N-acetyl-d-glucosamine (NAG) and N-methyl-d-glucamine (NMG), was also studied, and a comparison with GA was provided. NMG was the most reactive with CO2, whereas GA was the least reactive. This work will draw attention to this new category of CO2-capturing solvents.

Predicting the equilibrium solubility of CO2 in alcohols, ketones, and glycol ethers: Application of ensemble learning and deep learning approaches

In the present work, the solubility of CO2 in solutions comprising various physical solvents (Methanol, Ethanol, Propylene Glycol, n-Pentanol, n-Butanol, n-Propanol, Ethylene Glycol, 2-Butanone, 2-Methoxyethanol, 2-Ethoxyethanol, and Acetone) was modeled using machine learning approaches. In this regard, ensemble learning and deep learning approaches including Bagging Regressor with support vector regression (SVR) as the based estimator (Bagging_SVR), Adaptive Boosting Regressor with Decision Tree as the based estimator (ADA_DT), Decision Tree (DT), and Convolutional Neural Network (CNN) were developed. To develop the models, a broad set of CO2 solubility data (810 experimental data points for 11 alcohol, ketone, and glycol ether solvents) was acquired over various operating temperatures (283.15-373.15 K) and pressures (0.0142-57.38 MPa). In addition, the pressure, temperature, critical properties, and acentric factor of physical solvents were considered as the inputs to the machine learning approaches. To evaluate models’ performance, different graphical and statistical analyzes were conducted. The results revealed that the CNN model is more accurate than other proposed models. Root mean square error (RMSE) and determination coefficient (R2) values for CNN model were obtained as 0.016027 and 0.9943, respectively. Based on the sensitivity analysis, the dissolution of CO2 in physical solvents was highly affected by acentric factors as well as critical temperature and critical pressure. The use of leverage method showed that the used experimental data have high reliability and the CNN model also displayed high credit. Results of this study provide accurate models to estimate the solubility of CO2 in solutions containing physical solvents, which is more straightforward and user-friendly compared to thermodynamic methods with difficult calculations and procedures.

Prediction of CO2 solubility in multicomponent electrolyte solutions up to 709 bar: Analogical bridge between hydrophobic solvation and adsorption model

Prediction of CO2 solubility in electrolyte solution is important for the design of various industrial processes using CO2. A large amount of experimental data is needed to predict the solubility accurately, as a consequence of the complex composition of electrolyte solution. 1384 experimental CO2 solubility data in various electrolyte solutions (containing mostly Na+, Ca2+, Mg2+, K+, SO42−, and Cl−) from 30 references were used as training and validation data for developing a solubility model. According to the analogy between the hydrophobic solvation of CO2 and the adsorption phenomena, the novel solubility model with only four parameters (m0, α, k0, and k1) was developed to predict the CO2 solubility in solution with various ions. The model was correlated with the CO2 pressure and system temperature. The effect of dissolved electrolytes on the CO2 solubility was indicated by the concentration of electrostricted water molecule (ha) in the model, which was calculated using the concentration and hydration number of dissolved ions. The developed model with four parameters—obtained from experimental CO2 solubility data in water and single-salt solutions—reproduced the CO2 solubility well in complex electrolyte solutions, including the solutions after CO2–brine–rock reactions. Of the 1384 data, 94% were within a 95% prediction interval of the model. The model parameters can be used to estimate the heat of CO2 solvation, maximum CO2 solubility in water, and decay constant of the CO2 solubility with respect to the ha value. The developed model was further validated with single-salt solutions containing minor ions such as Li+ or Br−.

Solubility of CO2 in aqueous solutions of glycerol and monoethanolamine

For decades, carbon dioxide emissions have been an environmental and health issue. Amines like Monoethanolamine (MEA) have long been favoured in strategies based on chemical absorption aimed at CO2 capture and thus reduction of its harmful environmental impacts. However, some drawbacks, such as toxicity, low stability and high cost limit widespread adoption of this technology. New and green solvents are a possible solution to this issue. As a part of the present study, CO2 solubility in aqueous solutions of different molar ratios of MEA and glycerol as a green solvent was studied. The CO2 absorption was performed at three different temperatures (303, 318, and 333K) at normal atmospheric pressure, while CO2 partial pressure was varied from 1 to 15kPa, and the gas flow rate in the mixture was changed from 350 to 700ml/min. The response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and explore the effects of four independent parameters (molar concentration of MEA, molar concentration of glycerol, temperature, and gas flow rate) on the solubility of CO2 in solution. Analysis of variance (ANOVA) results showed a good agreement between the experimental data and the statistical model. The maximum solubility occurred for 4M MEA+2M glycerol at 333K and 350ml/min CO2 flow rate. The CO2 solubility values pertaining to different pressures and concentrations were in good agreement with the general absorption trend. However, as the temperature increased, so did the loading. The findings further revealed that the optimum CO2 solubility was obtained at low glycerol to MEA ratio, as this ensured the solubility at elevated temperatures. As glycerol is a viscous fluid, it can be confirmed that it is a suitable solvent at low pressures and high temperatures. Therefore, it can be a viable alternative solution for post-combustion CO2 capture. In addition, an artificial neural network (ANN) model and correlations of CO2 solubility with CO2 partial pressure for all the studied solvent mixtures were developed in this study. Both the ANN model and the correlations fit the experimental CO2 solubility data reasonably well.

CO2 solubility in aqueous solutions containing Na+, Ca2+, Cl−, SO42− and HCO3-: The effects of electrostricted water and ion hydration thermodynamics

Dissolution of CO2 into deep subsurface brines for carbon sequestration is regarded as one of the few viable means of reducing the amount of CO2 entering the atmosphere. Ions in solution partially control the amount of CO2 that dissolves, but the mechanisms of the ion's influence are not clearly understood and thus CO2 solubility is difficult to predict. In this study, CO2 solubility was experimentally determined in water, NaCl, CaCl2, Na2SO4, and NaHCO3 solutions and a mixed brine similar to the Bravo Dome natural CO2 reservoir; ionic strengths ranged up to 3.4 molal, temperatures to 140 °C, and CO2 pressures to 35.5 MPa. Increasing ionic strength decreased CO2 solubility for all solutions when the salt type remained unchanged, but ionic strength was a poor predictor of CO2 solubility in solutions with different salts. A new equation was developed to use ion hydration number to calculate the concentration of electrostricted water molecules in solution. Dissolved CO2 was strongly correlated (R2 = 0.96) to electrostricted water concentration. Strong correlations were also identified between CO2 solubility and hydration enthalpy and hydration entropy. These linear correlation equations predicted CO2 solubility within 1% of the Bravo Dome brine and within 10% of two mixed brines from literature (a 10 wt % NaCl + KCl + CaCl2 brine and a natural Na+, Ca2+, Cl− type brine with minor amounts of Mg2+, K+, Sr2+ and Br−).

Measurement and prediction model of carbon dioxide solubility in aqueous solutions containing bicarbonate anion

The solubility of CO2 in aqueous solutions containing bicarbonate anion was determined at 308.15, 328.15, 368.15, and 408.15K up to 40MPa. In comparison with Cl−, HCO3− has a larger size and higher molecular weight, which leads to the opposite salting-out effect. HCO3− can suppress CO2 dissolution because of equilibrium reaction between CO2 and H2O to form HCO3−. Cooperation of the three effects leads to slightly variable solubility of CO2 in the solution containing HCO3−. It is found that the Duan model can more accurately predict the CO2 solubility at low salt concentration, while the PR–HV model shows smaller error at high salt concentration. Moreover, the solubility of CO2 in natural ground water was measured at different temperatures and pressures, and the results verified the presented mathematical model.

Solubility of carbon dioxide in mixtures of 2-amino-2-methyl-1-propanol and organic solvents

Sterically hindered amines, such as 2-amino-2-methyl-1-propanol (AMP), are an interesting alternative to the amines used in conventional CO2 absorption processes in industrial applications. One reason for this is because the carbamate formed is not stable, which may be beneficial during the regeneration of the amine solution in terms of a reduced energy requirement.This paper presents experimental data on the solubility of CO2 in solutions of AMP in one of two organic solvents: N-methyl-2-pyrrolidone or triethylene glycol dimethyl ether, at different amine concentrations (15wt% and 25wt%) and temperatures (25°C and 50°C). A solid precipitate was observed during some of the experiments. The absorption capacity of the solution increased with AMP concentration and was higher at lower temperatures.

Influence of the enzyme concentration on the phase behaviour for developing a homogeneous enzymatic reaction in ionic liquid–CO2 media

A homogeneous enzymatic reaction in an ionic liquid (IL)–CO2 medium integrated with the separation of the product is proposed. It takes advantage of the miscibility switch phenomenon using CO2, which is able to force two immiscible phases to form one homogeneous phase to perform the reaction. After completion of the reaction the homogeneous fluid phase is split in two or three phases upon pressure decrease in order to facilitate the product recovery. For this purpose the enzymeCandida antarctica lipase B (CaL B) and the IL 1-hydroxy-1-propyl-3-methyl imidazolium nitrate (HOPMImNO3) are used. In this study the solubility of CO2 in solutions of CaL B in HOPMImNO3 was experimentally determined using the Cailletet apparatus, which operates according to the synthetic method. Concentrations of the enzyme vary from 3 to 12% by weight, and concentrations of CO2 from 5 to 20 mol% were investigated in a temperature range from 30 to 75 °C and pressures up to 12 MPa were applied. No precipitation of the enzyme was observed when dissolving CO2 in the IL. At constant CO2/IL ratios the pressure of the bubble points remained almost unchanged with the enzyme concentration. Triacetin tests showed that the reduction of the activity of the enzyme after storage for three months in liquid HOPMImNO3 was only of the order of 20%. Recovery and purification of the IL was possible by precipitation of the enzyme using isopropanol (IPA) as an anti-solvent.

Solubility of CO2 in Aqueous Piperazine and its Modeling using the Kent‐Eisenberg Approach

AbstractA systematic investigation of the equilibrium solubility of CO2 in aqueous piperazine solutions was conducted in a double‐jacketed stirred cell reactor. The solubilities of CO2 in the solution were measured at 20, 30, 40, and 50 °C with CO2 partial pressures ranging from 0.4–95 kPa. Generally the aqueous piperazine solution exhibits the same characteristics as conventional alkanolamines. Increasing the CO2 partial pressure increases the gas loading, however increasing the temperature or concentration decreases the CO2 loading. The values of the CO2 loading obtained confirm that the piperazine forms stable carbamates. The equilibrium solubility data were analyzed using a Kent‐Eisenberg approach. Representation of the model is generally in good agreement with that of the experimental data, especially at high temperature.