Measurement Of CO2 Solubility Research Articles

Quantitative structure‐property relationship techniques for predicting carbon dioxide solubility in ionic liquids using machine learning methods

AbstractIonic liquids (ILs) are considered unique and attractive types of solvents with great potential to capture carbon dioxide (CO2) and reduce its emissions into the atmosphere. On the other hand, carrying out experimental measurements of CO2 solubility for each new IL is time‐consuming and expensive. Whereas, the possible combinations of cations and anions are numerous. Therefore, the preparation and design of such processes requires simple and accurate models to predict the solubility of CO2 as a greenhouse gas. In the present study, two different models, namely: artificial neural network (ANN) and support vector machine optimized with dragonfly algorithm (DA‐SVM) were used in order to establish a quantitative structure–property relationship (QSPR) between the molecular structures of cations and anions and the CO2 solubility. More than 10 116 CO2 solubility data measured in various ionic liquids (ILs) at different temperatures and pressures were collected. 13 significant PaDEL descriptors (E2M, MATS8S, TDB6I, TDB1S, ATSC4V, MATS8M, ATSC7V, Gats2S, Gats5S, Gats5C, ATSC6V, DE, and Lobmax), temperature and pressure were considered as the model input data. For the test set data (2023 data point), the estimated mean absolute error (MAE) and R2 for the ANN model are of 0.0195 and 0.9828 and 0.0219 and 0.9745 for the DA‐SVM model. The results obtained showed that both models can reliably predict the solubility of CO2 in ILs with a slight superiority of the ANN model. Examination of sensitivity and outlier diagnosis examinations confirmed that the QSPR model optimized using the ANN algorithm is better suited to correlate and predict this property.

Hydrated carboxylate ionic liquids as chemical CO2 sorbents of high capacity and moderate enthalpy of absorption

Tetralkylphosphonium carboxylate ionic liquids are herein presented as efficient carbon dioxide chemisorbents in the presence of water. The ionic liquids tetrabutylphosphonium formate and acetate, tributylmethylphosphonium formate and a series of triethylalkylphosphonium formates and acetates, have been prepared by various synthetic procedures either from hydroxide or methylcarbonate precursors, or via multiple steps starting from the parent triethylphosphine. Their physicochemical properties, namely melting or glass transition temperatures, thermal decomposition behaviour, densities and viscosities have been determined. As dry substances, they are viscous liquids or low-melting solids, whereas they show little tendency to solidify in their hydrated forms. They were used mostly as monohydrates in CO2 solubility measurements, exhibiting highest capacities (3 mol L−1, i.e. ≈ 0.9 molCO2 molIL−1, at 5 bar, 25 °C) at equimolar H2O/ionic liquid ratios, approaching those of commercial aqueous amine sorbents. Carbon dioxide chemisorption into hydrogencarbonate takes place, as demonstrated by infrared spectroscopy with isotopic labelling. CO2 absorption isotherms were recorded at various temperatures and the data used to estimate the heat of absorption according to three different thermodynamic models. Enthalpies of CO2 absorption depended heavily on the model used. Rationalisation of this was done on the grounds of the expected relevance of physical and chemical sorption processes. Average heats of CO2 absorption lie between −40 and −45 kJ mol−1, in accordance with mild chemical absorption albeit significantly lower than those for typical chemical sorbents such as amines. This reinforces the feasibility of hydrated carboxylate ionic liquids for CO2 capture technologies of low regeneration energies.

High-pressure solubility measurement and eNRTL thermodynamics modeling of carbon dioxide in aqueous solutions of 2-((2-aminoethyl) amino) ethanol + dimethyl sulfoxide at different conditions

We measured the solubility of carbon dioxide in the aqueous solution of 2-((2-aminoethyl) amino) ethanol (AEEA) as a chemical solvent plus dimethyl sulfoxide (DMSO) as a physical solvent. A quasi-static high-pressure equilibrium cell was used for the measurement of CO2 solubility in the AEEA + DMSO + H2O systems at the compositions of (10, 20, 70), (15, 15, 70), (20, 10, 70), (25, 5, 70) wt. %. We performed the experiments at temperatures of 318.15, 328.15, and 343.15 K and pressures up to 5000 kPa. Also, we compared the CO2 solubility in the aqueous mixture of 2-((2-aminoethyl) amino) ethanol (AEEA) + dimethyl sulfoxide (DMSO), 2-((2-aminoethyl) amino) ethanol (AEEA) + sulfolane, methyl diethanolamine (MDEA) + dimethyl sulfoxide (DMSO), and methyl diethanolamine (MDEA) + sulfolane. We used the Electrolyte-NRTL thermodynamic model to correlate the solubility of CO2 in the aqueous solutions of AEEA + DMSO and to predict the partial pressure of CO2 versus the acid gas loading. The present modeling provided an excellent representation of the experimental data over the whole temperature range for 121 experimental data, which resulted in an average absolute deviation of 12.96 %.

Utilization of CO2 as a physical blowing agent for foaming of high temperature sulfone polymers

The present work adopts the one-step batch foaming technique to develop microcellular foams from polysulfone (PSU) and polyethersulfone (PES) using supercritical carbon dioxide (CO2) as a physical blowing agent. The results illustrates that the high temperature polymers can successfully generate highly uniform cellular structures with CO2, exhibiting cell densities in the order of 1010 cells/cm3 but limited volume expansion ratios of up to 4 times. The cell densities of both systems, PSU/CO2 and PES/CO2, were observed to be highly affected by the foaming pressure, showing significant enhancement of over 5 orders of magnitude with an increase in pressure from 3.4 to 13.8 MPa. On the other hand, the expansion ratio showed a strong dependence on the foaming temperature. Especially, the foams produced at pressures below 13.8 MPa exhibited a unique double peak behavior consisting of two maximum expansion ratios obtained at two different temperatures. In the temperature range of the first expansion peak, nanostructures were observed on the cell walls of the foams. The surficial features appeared in the form of a nanofibril network and gradually disappeared as the temperature approached the region of the second peak. Based on the observation, the unique double peak behavior may be correlated to the presence of the nanostructures. The work also encompassed measurement of CO2 solubility and high pressure thermal analysis of the two polymers, which were incorporated in the discussion of the distinctive foaming behavior.

Equilibrium Solubility Measurement and Modeling of CO2 Absorption in Aqueous Blend of 2-(Diethyl amino) Ethanol and Ethylenediamine

The equilibrium CO2 solubility in an aqueous blend of 2-(diethyl amino) ethanol (DEEA) and ethylenediamine (EDA) was performed at atmospheric pressure with the use of a laboratory scale bubbling absorber. The total concentration of amine blend solution in the range of 1.13–4.90 mol·kg–1 and the EDA mole fraction in the total amine blend in the range of 0.05–0.20 were taken. The experiments for the measurement of CO2 solubility were performed at a temperature range of 303.15–333.15 K and CO2 partial pressure range of 10.13–20.27 kPa. The analysis of CO2 in the liquid phase was accomplished by a direct titration method using HCl solution. The solubility data of CO2 in DEEA+EDA solution of the present study were compared with data available in the literature. The experimental results were applied to develop an empirical mathematical model with an average absolute deviation of 7.03% to predict the CO2 equilibrium solubility in DEEA+EDA solution within the specified range of operating conditions. In addition, ...

Thermodynamic study of the CO2 – H2O – NaCl system: Measurements of CO2 solubility and modeling of phase equilibria using Soreide and Whitson, electrolyte CPA and SIT models

The thermodynamic study of the CO2-H2O-NaCl system is of great importance whether in an environmental context as part of Carbon Capture and Storage (CCS) or in an economic context such as enhanced oil recovery by CO2 injection, or massive and reversible underground storage for industrial use (methanation, fermentation, water treatment, carbonation of drinks, etc.). In this work, using a new set-up based on the “static-analytic” method, measurements of CO2 solubility in aqueous sodium chloride solution were performed at molalities between 1 and 3 m, at temperatures between 50 and 100 °C and pressures up to 230 bar. For the modeling part, an electrolyte version of the PR-CPA (Peng-Robinson Cubic Plus Association) equation of state was developed under the name “e-PR-CPA”, as well as modified Soreide and Whitson (m-SW) model was used and improved. These two models using the phi-phi approach are compared with two geochemical models (Corvisier 2013 and Duan el al. 2006) using the gamma-phi approach, and against the literature and measured data. The measured data are in good agreement with the literature data and model predictions. Under geological storage conditions, the e-PR-CPA and Duan models estimate solubility slightly better (Average Absolute Deviation less than 6.6%) than the m-SW model and the geochemical model (AAD less than 7.6%).

High pressure CO2 solubility in food model solutions and fruit juices

Measurements of CO2 solubility were performed in different media, pure water, model citrate buffer solutions at different pH values and in the presence of different sugar content and in real apple and carrot juices. Solubility was determined in the pressure range from 8 to 20 MPa and in the temperature range from 308 to 318 K. CO2 solubility in citrate buffer solutions at pH = 3.8 and pH = 6.2 was slightly lower than CO2 solubility in pure water. A Chrastil-type equation according to Fornari’s approach was used to fit CO2 solubility data in pure water and model solutions. A new term was introduced in this equation to account for the decrease in solubility of CO2 in the presence of sugar in the liquid media.

Experimental Measurement of CO2 Solubility in Aqueous CaCl2 Solution at Temperature from 323.15 to 423.15 K and Pressure up to 20 MPa Using the Conductometric Titration

In the framework of the efforts of the scientific community developed for the reduction of CO2 emissions, the geological storage of CO2 in deep saline aquifers is under focus. An increase of salinity decreases the potential of CO2 solubilization into the water. In salty waters, the salinity is not only due to NaCl but also to others ions and in particular Ca and Mg. Experimental solubility data of CO2 in calcium chloride solution available in the literature at conditions relevant to carbon storage are particularly scarce. In this work, a new analytical method was developed for experimental measurement of CO2 solubility in calcium chloride solutions (1, 3, and 6 mol/kg) at high pressures (5–20 MPa) and temperatures (323.15, 373.15, and 423.15 K). This method is based on conductometric titration coupled with classical pH titration. The conductimetry shows sharper curves than the pH titration allowing a higher precision. Thirty-six new experimental data are reported in this paper. These data presented an exp...

Carbon dioxide loading capacity in aqueous solution of Potassium salt of Proline blended with Piperazine as new absorbents

In this work aqueous solution of potassium prolinate (KPr) blended with piperazine (PZ) have been utilized through CO2 solubility measurements in order to investigate the possible use of these salts of amino acid blended with alkanolamine for CO2 absorption. The equilibrium solubility of CO2 for KPr blended with PZ solutions at 1.0, 4.0 and 10.0wt.% overall mass concentration is experimentally measured with an equilibrium cell at CO2 partial pressure ranging from 4.8 to 2383.2kPa and temperatures between 293.15 and 323.15K. Obtained data showed that loading capacity decreases with an increase in temperature and concentration of KPr. Obtained CO2 loadings are very high at low concentration of KPr. In order to predict CO2 solubility in KPr blended with PZ, Deshmkh-Mather model is extended. The values of MSE, ARD and R2 for the extended Deshmukh-Mather model are 0.0363, 10.7770 and 0.9844, respectively.

Experimental and theoretical study of carbon dioxide solubility in aqueous solution of potassium glycinate blended with piperazine as new absorbents

In this work aqueous solution of potassium glycinate, piperazine and potassium glycinate blended with piperazine have been utilized through CO2 solubility measurements in order to investigate the possible use of these salts of amino acid blended with alkanolamine for CO2 absorption. The equilibrium solubility of CO2 for aqueous solutions of potassium glycinate, piperazine and potassium glycinate blended with piperazine at 1.0, 4.0 and 10.0wt.% overall mass concentration are experimentally measured with an equilibrium cell at CO2 partial pressure ranging from 5.1 to 2508.7kPa and temperatures between 293.15 and 323.15K. Obtained data show that loading capacity decreases with increase in temperature and concentration of potassium glycinate and potassium glycinate blended with piperazine. Obtained CO2 loadings are very high at low concentration of potassium glycinate. In order to predict CO2 solubility in aqueous solutions potassium glycinate, piperazine and potassium glycinate blended with piperazine, Deshmkh-Mather model is extended. The values of MSE, ARD and R2 for the extended Deshmukh-Mather model are 0.0741, 8.9582 and 0.9826, respectively. In addition, an artificial neural network (ANN) is developed to predict CO2 solubility in aqueous solutions of piperazine, potassium glycinate and potassium glycinate blended with piperazine. The values of MSE, ARD and R2 for the optimal trained ANN are 0.0179, 4.1528 and 0.9962, respectively.

Direct measurement of CO2 solubility and pH in NaCl hydrothermal solutions by combining in-situ potentiometry and Raman spectroscopy up to 280 °C and 150 bar

The in-situ monitoring of aqueous solution chemistry at elevated temperatures and pressures is a major challenge in geochemistry. Here, we combined for the first time in-situ Raman spectroscopy for concentration measurements and potentiometry for pH measurement in a single hydrothermal cell equipped with sampling systems and operating under controlled conditions of temperature and pressure. Dissolved CO2 concentration and pH were measured at temperatures up to 280°C and pressures up to 150bar in the H2O–CO2 and H2O–CO2–NaCl systems. A Pitzer specific-ion-interaction aqueous model was developed and confirmed the accuracy and consistency of the measurements, at least up to 250°C. The revised Pitzer parameters for the H2O–CO2–NaCl system were formatted for the Phreeqc geochemical software. Significant changes with respect to the Pitzer.dat database currently associated with Phreeqc were observed. The new model parameters are now available for further applications. The Raman and pH probes tested here may also be applied to field monitoring of hydrothermal springs, geothermal wells, and oil and gas boreholes.

Experimental measurements of carbon dioxide solubility in aqueous tetra-n-butylammonium bromide solutions

In this paper, we report the absolute measurements of CO2 solubility in aqueous tetra-n-butylammonium bromide (TBAB) solution. The measurement range was 0.2MPa<P<4MPa, 286.15K<T<298.15K, with 0 (pure water)<wTBAB<0.4, where P, T, and wTBAB denote the pressure, temperature, and mass fraction of TBAB in the aqueous feed solutions, respectively. These thermodynamic conditions are outside the hydrate formation region. We evaluated salting-in and -out effects based on the experimental data, and confirmed that the CO2 salting-out effect of TBAB clearly appeared at T=292K with wTBAB<0.32 and the salting-in effect may exist for P>3MPa and T>292K with wTBAB⩾0.4 mass fraction of TBAB.

Equilibrium solubility of carbon dioxide in aqueous solutions of 3-amino-1-propanol, 4-amino-1-butanol and 5-amino-1-pentanol at low partial pressures

Vapor liquid equilibrium (VLE) data of CO2 solubility in aqueous amine solutions are essential for solving problems associated with flue gas purification. This work presents new VLE data of 3-amino-1-propanol, 4-amino-1-butanol and 5-amino-1-pentanol, respectively. An equilibrium cell, connected to a gas chromatograph was first utilized to measure the partial pressures of CO2 over 2-amino-1-ethanol (MEA). The setup was validated against literature data and is capable of producing reliable and reproducible results. Measurements of CO2 solubility in these primary alkanolamines at two different concentrations (5 molar and 30wt%) were performed at a temperature of 40°C. Results showed that these amines have higher CO2 solubility than MEA, and we found that increasing the chain length increase the solubility of CO2.

Modeling and measurement of CO2 solubility in salty aqueous solutions and application in the Erdos Basin

Geological carbon storage (GCS) is recognized as an effective method for mitigating the greenhouse effect. Deep saline aquifers hold the highest potential capacity for CO2 storage. CO2 solubility in salty aqueous solutions under geological sequestration conditions plays a key role in GCS. However, most CO2 solubility studies focus mainly on single-salt solutions (NaCl and CaCl2), and extrapolation of these studies to aqueous solutions with mixed ions is unavailable. To fill the research gap, based on the collection of CO2 solubility data, a semi-empirical thermodynamic model is proposed in this paper to calculate CO2 solubility in aqueous solutions containing K+, Na+, Ca2+ and Mg2+ in the temperature and pressure ranges from 313K to 378K and from 50bar to 220bar. To describe the CO2–liquid phase equilibrium, the Peng–Robinson equation of state (PR EoS) and the Setschenov equation are applied. The former has been modified to improve its performance in the studied T–P range, and the latter shows excellent accuracy with only three optimized parameters. Before modeling was done, experimental studies were conducted. Brine sampling from five reservoirs potentially chosen for CO2 sequestration in the Erdos Basin was carried out using a monitoring well in the support of the Shenhua Group carbon capture and storage (CCS) site project. The chemical composition of the samples was determined, and experiments measuring CO2 solubility were carried out in synthetic brine with 64 valid data points reported. An analytical method with a simplified sampling technique was chosen. In the range studied, the average absolute deviation of CO2 solubility between the model and experimental results was 2.01%, and the maximum absolute deviation in this study was less than 4.79%. The proposed model and experimental data therefore possess broad adaptability to GCS with satisfactory accuracy.

CO₂ Capture and Separation Properties in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Nonafluorobutylsulfonate.

Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO2 in ILs. In the present work, solubility measurements of CO2 in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate [C4mim][CF3CF2CF2CF2SO3] were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H2, N2, and O2 in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry’s law constants, enthalpies, and entropies of absorption for CO2 in the IL were also determined and presented. The CO2 solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO2 in these ILs follows the sequence: [C4mim][CF3CF2CF2CF2SO3] ≈ [C4mim][Tf2N] > [C4mim][CF3CF2CF2COO] > [C4mim][BF4], and the solubility selectivity of CO2 relative to O2, N2, and H2 in [C4mim][CF3CF2CF2CF2SO3] was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO2.

Solubility of CO2 in and Density, Viscosity, and Surface Tension of Aqueous 2-Amino-1,3-propanediol (Serinol) Solutions

In this work, 2-amino-1,3-propanediol (Serinol) aqueous solutions were characterized through density, viscosity, surface tension and CO2 solubility measurements in order to evaluate the potential use of this alkanolamine for CO2 removal from different gas mixtures. Density and viscosity were measured from temperature T = (293.2 to 313.2) K and for amine concentrations from molality m = (0.953 to 4.693) mol·kg–1. Surface tension data were measured for the same solution concentrations but at T = (298.2 and 313.2) K. CO2 solubility in Serinol solutions from m = (0.953 to 4.704) mol·kg–1 was determined at T = 313.15 K and at T = (343.15 and 373.15) K for the m = 4.704 mol·kg–1 solution. CO2 loading capacities were compared to literature data for monoethanolamine (MEA) and those obtained for (2.712 + 1.161) mol·kg–1 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) + piperazine (Pz) solution at T = (313.15 and 373.15) K. It was found that Serinol solutions have higher surface tensions compared to conventional abs...

Experimental measurements and modeling of CO2 solubility in sunflower, castor and rapeseed oils

In this work solubility measurements of CO2 in three vegetable oils, a high oleic sunflower oil (HOSO), a castor oil and a rapeseed oil, for mole fractions ranging from 0.32 to 0.93 in the temperature range 298–363K and up to 75MPa were performed. Moreover, the densities and viscosities of these oils are reported from 278.15 to 373.15K at atmospheric pressure. These data were used to evaluate the predictive ability of the fragment based approach. Solubility data were modeled by means of the SRK EoS and predicted employing the Carvalho and Coutinho correlation. Global average deviations inferior to 6% in CO2 mole fraction composition were achieved with the SRK EoS and maximum percentage absolute average deviations of 13% in pressure were obtained using the Carvalho and Coutinho correlation.

Quantum chemistry calculation and experimental study of CO2/CH4 and functional group interactions for the design of solubility selective membrane materials

The separation of CO2 from CH4 in the natural gas sweetening process would benefit from a membrane material which has a high solubility selectivity between these two molecules. In this study, quantum chemistry calculations were used to screen a set of twelve representative functional groups by comparing their CO2 and CH4 binding energies, as well as the binding energy differences. The calculation results indicate that non-base groups, such as acids and their salts, may help improve the solubility selectivity of polymeric membrane materials for CO2 over CH4. Experimental measurements of CO2 solubility in polyacrylic acid (PAA) confirmed that acid groups can help absorb CO2 and enhance the selectivity over CH4. However, the selectivity increase due to the acid functional group is not exceptional. Further quantum chemistry study of functional group interactions reveals that strongly polar functional groups can have self-interactions and form “dimers” in the polymer. The formation of functional group dimers may decrease the solubility of CO2 because of their weaker interactions with CO2 than isolated functional groups. In addition, our calculations show that water can interact more favorably with polar functional groups than CO2. Therefore the presence of water may decrease CO2 solubility.

Multimodel Predictive System for Carbon Dioxide Solubility in Saline Formation Waters

The prediction of carbon dioxide solubility in brine at conditions relevant to carbon sequestration (i.e., high temperature, pressure, and salt concentration (T-P-X)) is crucial when this technology is applied. Eleven mathematical models for predicting CO(2) solubility in brine are compared and considered for inclusion in a multimodel predictive system. Model goodness of fit is evaluated over the temperature range 304-433 K, pressure range 74-500 bar, and salt concentration range 0-7 m (NaCl equivalent), using 173 published CO(2) solubility measurements, particularly selected for those conditions. The performance of each model is assessed using various statistical methods, including the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). Different models emerge as best fits for different subranges of the input conditions. A classification tree is generated using machine learning methods to predict the best-performing model under different T-P-X subranges, allowing development of a multimodel predictive system (MMoPS) that selects and applies the model expected to yield the most accurate CO(2) solubility prediction. Statistical analysis of the MMoPS predictions, including a stratified 5-fold cross validation, shows that MMoPS outperforms each individual model and increases the overall accuracy of CO(2) solubility prediction across the range of T-P-X conditions likely to be encountered in carbon sequestration applications.

Reaction kinetics of CO2 absorption in to phosphonium based anion-functionalized ionic liquids

The reaction kinetics between CO2 and trihexyl(tetradecyl)phosphonium ([P66614])-based ionic liquids (ILs) with prolinate ([Pro]), 2-cyanopyrrolide ([2-CNpyr]), and 3-(trifluoromethyl)pyrazolide ([3-CF3pyra]) anions are studied at temperatures from 22-60 °C. The absorption of CO2 is carried out in a stirred reactor under pseudo first order conditions. ILs are diluted to concentrations of 0.05, 0.1 and 0.15 M with tetraglyme--a nonreactive, low volatility solvent with much lower viscosity than the ILs. Physical solubility of CO2 in the mixtures is calculated using correlations developed from CO2 solubility measurements in tetraglyme and the N2O-analogy for ILs and dilute IL solutions. The diffusivity of CO2 is estimated from viscosity-dependent correlations chosen after a thorough literature review. The results indicate partial first order reaction kinetics with respect to IL with values ranging from 19,500 L mol(-1) s(-1) ([P66614][Pro]) to 3200 L mol(-1) s(-1) ([P66614][3-CF3pyra]) at 22 °C. The second order reaction rate constants follow Arrhenius behavior with the highest activation energy of 43 kJ mol(-1) measured for [P66614][Pro]. ILs with aprotic heterocylic anions (AHA), on the other hand, show small activation energies of 18 and 11 kJ mol(-1) for [P66614][3-CF3pyra] and [P66614][2-CNpyr], respectively. The ILs studied in this work exhibit reactivity comparable to or higher than common aqueous amines. High reaction rates and tunable capacity make ILs, and AHA ILs in particular, attractive solvents for CO2 separations.