Experimental study on equilibrium solubility (at low partial pressures), density, viscosity and corrosion rate of carbon dioxide in aqueous solutions of ascorbic acid

In this paper, ascorbic acid as a new carbon dioxide (CO₂) absorbent was investigated. The equilibrium solubility of CO₂ into 0.5, 1 and 1.5 mol dm⁻³ (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO₂ partial pressure ranging from 0 to 45 kPa and temperatures between 298 and 313 K. The results of the gas solubility are presented as loading capacity (mol CO₂/mol ascorbic acid) as function of partial pressure of CO₂ for all experimental runs. Experimental results showed that solubility of CO₂ increases with increase in molar concentration of ascorbic acid solution at a given temperature and decreases with increase in temperature at a given concentration. The densities and viscosities of the ascorbic acid solutions were measured at the same conditions of the solubility measurement. Some corrosion rate tests were also performed on carbon steel at temperature of 308 K. It was observed that viscosity and corrosion rate increase when the molar concentration of ascorbic acid solution increases.     

Vapor–liquid equilibria of the carbon dioxide (CO2) + 2,2-dichloro-1,1,1-trifluoroethane (R123) system and carbon dioxide (CO2) + 1-chloro-1,2,2,2-tetrafluoroethane (R124) system

Binary vapor–liquid equilibrium data were measured for the carbon dioxide (CO₂) + 2,2-dichloro-1,1,1-trifluoroethane (R123) system and the carbon dioxide (CO₂) + 1-chloro-1,2,2,2-tetrafluoroethane (R124) system at temperature from 313.15 to 333.15 K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by Peng–Robinson equation of state using the Wong–Sandler mixing rules.     

Solubility of carbon dioxide in aqueous solution of 2-amino-2-methyl-1-propanol and piperazine

In this work, new experimental results of the vapour-liquid equilibrium (VLE) of CO₂ in aqueous 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) have been presented in the temperature range of 298-328 K and PZ concentration range of 2-8 mass%, keeping the total amine concentration in the solution at 30 mass%. The partial pressures of CO₂ were in the range of 0.1-1450 kPa. A thermodynamic model was developed to correlate and predict the VLE of CO₂ in aqueous AMP + PZ. The electrolyte nonrandom two liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO₂ + AMP + PZ + H₂O) to describe the equilibrium behaviour of the solution. The experimental data from this work and data available in the literature were used to regress the ENRTL interaction parameters. The model predictions are in good agreement with the experimental data of CO₂ solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, pH of the CO₂ loaded solution, and amine volatility.     

Equilibrium solubility of carbon dioxide in a 30 wt.% aqueous solution of 2-((2-aminoethyl)amino)ethanol at pressures between atmospheric and 4400 kPa: An experimental and modelling study

New experimental equilibrium data were obtained for the solubility of carbon dioxide in an aqueous solution with 30 wt.% of 2-((2-aminoethyl)amino)ethanol (AEEA) at temperatures ranging from (313.2 to 368.2) K and CO₂ partial pressures ranging from above atmospheric to 4400 kPa. A thermodynamic model based on the Deshmukh–Mather method was applied to correlate and predict the CO₂ solubility in aqueous AEEA solutions. The binary interaction parameters and equilibrium constants for the proposed reactions were determined by data regression. Using the adjusted parameters, equilibrium partial pressures of CO₂ were calculated and compared with the corresponding experimental values at the selected temperatures and pressures. Values of carbon dioxide solubility at other temperatures reported in the literature were also calculated. The average absolute deviation for all of the data points was found to be 8.2%. The enthalpy change of the absorption of CO₂ in the 30 wt.% aqueous solution of AEEA was also estimated with our model.     

High-pressure phase behavior of CO2 + 1-butyl-3-methylimidazolium chloride system

The phase behavior of carbon dioxide (CO₂) and the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) was measured and correlated at high pressures up to ∼40 MPa and at temperatures between 353.15 K and 373.15 K. The solubility data of CO₂ in [bmim][Cl] were obtained by observing the bubble point pressure at specific temperatures. A variable-volume view cell, which is a high-pressure equilibrium apparatus, was used to measure the CO₂ + [bmim][Cl] system solubility under varying pressure and temperature conditions. In addition, liquid–liquid–vapor (LLV) three-phase behavior was investigated using the equilibrium cell to be able to determine the classification of phase-behavior type by Scott and Van Konynenburg. Based on the LLV phase behavior, this system most likely has type III phase-behavior which is common for IL + CO₂ systems. The resulting data showed that CO₂ dissolved well in the IL at low CO₂ concentrations, but that the pressure derivative of CO₂ solubility dramatically decreased as the mole fraction of CO₂ was increased. The experimental data were well fitted by the Peng–Robinson equation of state with a quadratic mixing rule and cubic parameters estimated by the Joback method.     

Solubility of carbon dioxide in aqueous solutions of diisopropanolamine and methyldiethanolamine

The solubility of carbon dioxide in aqueous solutions of alkanolamines was measured by means of two experimental methods. The solubility of carbon dioxide was measured at 298 K with a static total pressure apparatus in solutions of water + diisopropanolamine (DIPA) having mass fraction of DIPA equal to 10.1%, 11.0% and 33.9%. The density of the water + DIPA solution was measured continuously during the experiments to investigate the changes in density introduced by the absorption of carbon dioxide. A correlation for the density of CO₂-loaded aqueous solutions of DIPA is presented.     

Measurement and correlation of solubilities of C.I. Disperse Red 73, C.I. Disperse Yellow 119 and their mixture in supercritical carbon dioxide

The solubilities of disperse dyes and their mixture in supercritical carbon dioxide are important to the fundamental research and development of supercritical fluid dyeing (SFD). The solubilities of Disperse Red 73, Disperse Yellow 119 and their mixture in supercritical carbon dioxide were measured in the temperature range from 343 to 383 K and pressures from 12 to 28 MPa by a static-recirculation method. The results show that over the entire range of experimental conditions in the binary (Disperse Red 73 + CO₂ and Disperse Yellow 119 + CO₂) and ternary (Disperse Red 73 + Disperse Yellow 119 + CO₂) systems, the solubilities increased with increasing pressure and temperature and were clearly affected by the molecular polarity of the dyes. A co-solvent effect and a competing dissolution effect existing in the ternary system led to the increase and decrease in the solubilities of Disperse Yellow 119 and Disperse Red 73, respectively. The solubility data of the two dyes and their mixture were correlated with two empirical models—the Chrastil and the Mendez-Santiago/Teja (MT) model.     

The solubility of CO2 and N2O in olive oil

The solubility of CO₂ and N₂O in olive oil has been measured at temperatures of about 298, 310, and 323 K with a gravimetric microbalance under pressures up to 2 MPa. The molecular weight of olive oil has been analyzed and found to be about 882 g mol⁻¹ as a mixed oil compound. The observed solubility data have been correlated with a cubic equation of state (EOS) model. N₂O has a larger solubility than CO₂ in olive oil based on either the mole or mass fraction. The present results clarify some ambiguities from the previous N₂O solubility data in the literature.     

Acid gases partial pressures above a 50 wt% aqueous methyldiethanolamine solution: Experimental work and modeling

Aqueous amine solutions are widely used in the industry for acid gas removal. In order to treat natural gas or refinery process streams, an accurate knowledge of solubility data of carbon dioxide, hydrogen sulfide and other sulfur species in aqueous amine solutions is required. In this paper, new equilibrium measurements on 50 wt% aqueous methyldiethanolamine solution with CO₂ and H₂S have been produced. A simple way to correlate the data has been searched and found. First, a model proposed by Posey et al. in 1996, then a Deshmukh–Mather model are used to correlate “vapor–liquid” equilibria. The Posey et al. model lacks accuracy to represent the experimental data, especially for high loadings. The Deshmukh–Mather model shows good agreement as long as the total loading (H₂S + CO₂) does not reach 1.0.     

Solubility of carbon dioxide in 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate

Experimental results for the solubility of carbon dioxide in the ionic liquid 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate are not reported in the literature. To this end, we present in this work new solubility data for carbon dioxide in 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate for temperatures ranging from (303.2 to 343.2) K and pressures up to 6.7 MPa using a thermogravimetric microbalance. The carbon dioxide solubility was determined from absorption saturation (equilibrium) data at each fixed temperature and pressure. The buoyancy effect was accounted in the evaluation of the carbon dioxide solubility. Highly accurate equations of states for carbon dioxide and for ionic liquids were employed to determine the effect of buoyancy on carbon dioxide solubility. The solubility measurements are presented as a function of temperature and pressure. The present experimental solubility results have been successfully correlated using an extended Henry’s law equation.     

Isothermal vapour–liquid equilibria in the binary and ternary systems consisting of an ionic liquid, 1-propanol and CO2

Vapour–liquid equilibrium measurements for binary and ternary systems containing carbon dioxide, 1-propanol, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquids are presented in this work. The binary CO₂ + 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide system at 313.15 K at pressure range from 2 to 14.4 MPa was examined. The obtained phase envelop shows that even at low pressure of CO₂ the solubility of the gas in the ionic liquid is high. The ternary phase equilibria were studied at 313.15 K and pressures in the range from 9 to 12 MPa. The ternary phase diagrams show that higher CO₂ pressure diminishes the miscibility gap.     

Phase behaviour of 1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide with thiophene and aliphatic hydrocarbons: The influence of n-alkane chain length

This paper reports the results of a new experimental study on the capacity of an ionic liquid to extract a sulfur compound from its mixtures with aliphatic hydrocarbons. With this aim, liquid + liquid equilibrium data of ternary systems containing 1-methyl-3-octyl-imidazolium bis(trifluoromethylsulfonyl)-imide ([C₈mim][NTf₂]), thiophene and n-hexane, n-heptane or n-hexadecane have been determined at T = 298.15 K. All systems showed high solubility of thiophene in the ionic liquid and low solubility of the ionic liquid in the n-alkane. The solute distribution coefficient decreases and the selectivity increases as the chain length of n-alkane increases. Both parameters are higher than unity in most of the cases. The experimental results have been correlated using NRTL activity coefficient model, and large deviations from experimental data have been found at high concentrations of thiophene with the heaviest hydrocarbons.     

Thermodynamic modeling of CO2 solubility in ionic liquid with heterosegmented statistical associating fluid theory

Heterosegmented statistical associating fluid theory is used to represent the CO₂ solubility in ionic liquids. As in our previous work, ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modeled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modeled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate. Carbon dioxide is modeled as a molecule with three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other. The parameters of CO₂ are obtained from the fitting of the density and the saturation vapor pressure of CO₂. For the CO₂-ionic liquid systems, cross association between site of type C in CO₂ and another association site in anion is allowed to occur to account for the Lewis acid–base interaction. The parameters for cross association interactions and the binary interaction parameters used to adjust the dispersive interactions between unlike segments are obtained from the fitting of the available CO₂ solubility in ionic liquids. The model is found to well represent the CO₂ solubility in the imidazolium ionic liquids from 283 to 415 K and up to 200 bar.     

Modeling solubility of acid gases in alkanolamines using the nonelectrolyte Wilson-nonrandom factor model

The nonelectrolyte Wilson-nonrandom factor local composition model (N-Wilson-NRF) by Haghtalab and Mazloumi is applied for modeling the vapor–liquid equilibrium of the acid gases (CO₂ and H₂S)–alkanolamine–water systems. The model is used to calculate the nonideality of species in liquid phase through the activity coefficient equations. In this work, we use the N-Wilson-NRF model for short-range forces in the aqueous electrolyte system of alkanolamines by using the concept of ion-pair. For the long-range interaction the Pitzer–Debye–Hückel theory is applied. The model is used to correlation of the solubility data of CO₂ and H₂S in aqueous monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and 2-amino-2methyl-1-propanol (AMP) systems over wide range of temperature (0–140 °C), partial pressure (0.001–1000 kPa) and acid gases loading (0.001–1.0 mol gas/mol amine). To show the predictability of the model, the interaction parameters without any additional adjustable parameters are used to predict the solubility of CO₂ in aqueous AMP solution at different conditions. The results of the model show a very good agreement with the experimental data.     

Solubility of carbon dioxide in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

In this work, the phase behaviour of the binary system of carbon dioxide and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf₂N]) has been studied experimentally. The equipment used for the experiments is the Cailletet set-up, based on visual observations of phase transitions of systems with constant overall composition. Results are reported for carbon dioxide concentrations ranging from 12.3 to 59.3 mol%, and within temperature and pressure ranges of 310–450 K and 0–15 MPa, respectively. The data reveal an extremely high capacity of the selected ionic liquid for dissolving CO₂ gas, for example, reaching up to about 60 mol% within the above-mentioned pressure and temperature range. Also, the solubility of CO₂ in the ionic liquid [emim][Tf₂N] is compared to the solubility of CO₂ in the ionic liquid [emim][PF₆], an ionic liquid that shares the same cation.     

Solubilities of CO2 in hydroxyl ammonium ionic liquids at elevated pressures

Solubilities of CO₂ in eight hydroxyl ammonium ionic liquids 2-hydroxy ethylammonium formate (HEF), 2-hydroxy ethylammonium acetate (HEA), 2-hydroxy ethylammonium lactate (HEL), tri-(2-hydroxy ethyl)-ammonium acetate (THEAA), tri-(2-hydroxy ethyl)-ammonium lactate (THEAL), 2-(2-hydroxy ethoxy)-ammonium formate (HEAF), 2-(2-hydroxy ethoxy)-ammonium acetate (HEAA) and 2-(2-hydroxy ethoxy)-ammonium lactate (HEAL) at the temperatures ranging from 303 to 323 K and the pressures ranging from 0 to 11 MPa were determined. The solubility data were correlated using Krichevisky–Kasarnovsky equation, from which Henry's constants and the partial volumes of CO₂ at different temperature were obtained. Results showed that Krichevsky–Kasarnovsky equation can correlate the solubilities of CO₂ in these hydroxyl ammonium ionic liquids (ILs) well. Comparison showed that the solubility of CO₂ in these eight hydroxyl ammonium ionic liquids was in sequence: THEAL > HEAA > HEA > HEF > HEAL > THEAA ≈ HEL > HEAF.     

(Vapour + liquid) equilibria (VLE) of CO2 in aqueous solutions of 2-amino-2-methyl-1-propanol: New data and modelling using eNRTL-equation

This work presents new experimental results for carbon dioxide (CO₂) solubility in aqueous 2-amino-2-methyl-1-propanol (AMP) over the temperature range of (298 to 328) K and CO₂ partial pressure of about (0.4 to 1500) kPa. The concentrations of the aqueous AMP lie within the range of (2.2 to 4.9) mol · dm^?3. A thermodynamic model based on electrolyte non-random two-liquid (eNRTL) theory has been developed to correlate and predict the (vapour + liquid) equilibrium (VLE) of CO₂ in aqueous AMP. The model predictions have been in good agreement with the experimental data of CO₂ solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, enthalpy of CO₂ loaded aqueous AMP, pH of the loaded solution, and AMP volatility.     

Solubility of CO2 in imidazolium-based tetrafluoroborate ionic liquids

The solubility of CO₂ in imidazolium ionic liquids (ILs), 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF₄]), 1-hexyl-3-methyl imidazolium tetrafluoroborate ([hmim][BF₄]) and 1-octyl-3-methyl imidazolium tetrtafluoroborate ([omim][BF₄]) was determined at 305-25 K and pressures from 1 to 9 MPa. The influence of chain length of alkyl substituents on the imidazolium cation on the solubility of CO₂ was investigated. The differences in solubility with chain length are in the sequence [omim][BF₄] > [hmim][BF₄] > [bmim][BF₄]. The solubility data were correlated by the extended Henry's law, and enthalpy, Gibbs free energy and entropy changes were obtained.     

High-pressure phase behaviour of binary (CO2 + nicotine) and ternary (CO2 + nicotine + solanesol) mixtures

This work paper presents vapour–liquid equilibrium (VLE) data for binary (CO₂ + nicotine) and ternary (CO₂ + nicotine + solanesol) mixtures, at 313.2 K and 6, 8 and 15 MPa. The (CO₂ + nicotine) system exhibits three phases (L₁L₂V) in equilibrium at 8.37 MPa. It is estimated that this system most likely follows the type-III phase behaviour. In the ternary system, the presence of solanesol in the vapour phase was detected only at the pressure of 15 MPa. At this pressure, partition coefficients and separation factors for solanesol/nicotine were calculated for different initial nicotine/solanesol compositions and a strong influence of composition was found. The results were modelled using the Peng–Robinson equation of state (PR EOS) coupled with the Mathias–Klotz–Prausnitz (MKP) mixing rule (PR–MKP model). Good correlations of the binary data, particularly in the case of the (CO₂ + nicotine) mixture, were obtained. However, the model could not correlate the ternary data.     

High pressure vapor–liquid equilibrium measurements of carbon dioxide with naphthalene and benzoic acid

High pressure vapor–liquid equilibrium data for binary systems of carbon dioxide with naphthalene and benzoic acid were measured at three different temperatures for each system. Experimental temperatures and pressures ranged from 373 to 458 K and 0 to 22 MPa, respectively. Dew points were also measured for naphthalene in the CO₂ rich region. The data measured provides valuable solubility information and is used to derive gas–solvent group interaction parameters for the predictive Soave–Redlich–Kwong equation of state.