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In the treatment of many fuel gases such as biogas, natural gas, syngas, and so on, tertiary alkanolamines play an important role in the selective removal of H2S with respect to CO2. The selectivity might be required for various reasons: to respect more stringent H2S specifications, to optimize the performance of the Claus unit, to lower the cost of CO2capture, and so on. The H2S/CO2selectivity is mainly kinetic and, to a lesser extent, thermodynamic. A novel experimental setup has been put in place to measure the time evolution of the simultaneous absorption of H2S and CO2. The results of an extensive experimental campaign with 18 different aqueous tertiary alkanolamine solvents (13 mol % amine, 87 mol % H2O) are presented. Although the absorption of H2S is expected to be a very fast proton transfer, a significant variation in H2S absorption rates and thus in selectivity is observed. This could not only be explained by the pKaor the viscosity of the amines. Therefore, an accurate quantitative molecular simulations-based kinetic model is developed and validated. The study allowed us to better understand the molecular origin of selectivity, as well as to identify amines with a higher selectivity than aqueous MDEA (MethylDiEthanolAmine), the standard industrial selective solvent.

This paper reports new experimental data and calibrated semiempirical correlations concerning the density and viscosity of aqueous solutions of potassium lysinate (LysK), a promising bio-based solvent for postcombustion CO2capture from flue gases, an application of relevance for industrial decarbonization. The analysis covers a LysK molality range in the solution from 2.16 to 4.44 molLysK/kgH2O, temperature intervals between 288.15 and 358.15 K, and a CO2loading range of 0.3–0.98 molCO2/molLysK. Newly collected experimental results supported the development and calibration of semiempirical correlations for the density and viscosity of LysK solutions suitable to predict these thermophysical properties in the range of conditions tested. These models can predict the behavior of the thermophysical properties investigated with high accuracy (for loaded solutions, average absolute deviation for density equal to 1.48 kg/m3and for viscosity of 0.04 mPa s) within the whole range of LysK concentration, temperature, and CO2loading explored. Validation against literature data lying outside the calibration range shows an accuracy for density correlation ≤3%, while for the viscosity model, deviations are larger and vary between 1 and 15% of the measured value.

We have investigated the solubility of methanethiol and ethanethiol (methyl and ethyl mercaptans in an aqueous methyldiethanolamine solution (25 wt %)) by using a static analytic method at 333 and 365 K. The measurements were done for different pressures of methane in the absence of acid gas with individual acid gas present and with a mixture of acid gases present (CO2and/or H2S). Additional measurements of Henry’s law constants were realized by considering the gas stripping method. The effect of total pressure (realized by the addition of methane) and the effect of acid gas loading for a constant total pressure around 7 MPa were studied. The increasing pressure and acid gas loading increase the apparent Henry’s law constant of the mercaptan, highlighting a drop out effect of the mercaptans.

Dans le contexte actuel de la transition énergétique, le besoin de développer des solutions permettant de stocker temporairement l’énergie pousse à étendre les applications de stockage souterrain en cavité saline à de nouveaux fluides (parmi eux notamment l’hydrogène ou le dioxyde de carbone). Cependant, ces derniers fluides présentent des particularités thermodynamiques qu’il est important de bien caractériser et dont il faut anticiper l’impact sur le comportement global du stockage. Dans le cas du dioxyde de carbone, pris comme exemple d’application dans cet article, ces spécificités concernent l’état physique sous lequel il peut être stocké et sa forte solubilité dans la saumure également présente au fond de la cavité. Un modèle global de stockage est établi, permettant le couplage des comportements thermodynamique des fluides contenus et thermomécanique du massif salin, ainsi qu’une adaptation à chaque fluide pouvant être stocké. Ce modèle est ici étendu pour prendre en compte les nouveaux phénomènes liés au stockage de dioxyde de carbone, et tout particulièrement afin d’observer l’impact des échanges de matière avec la saumure sur les conditions de stockage. À cette fin, on compare les résultats de deux déclinaisons du modèle de stockage (à savoir prendre en compte ou non les transferts de masse) appliquées à différents scénarii d’opération : remplissage de la cavité, injection et extraction selon que le dioxyde de carbone est stocké sous forme liquide ou gazeuse. L’étude souligne l’intérêt d’appliquer le modèle étendu à toutes les modélisations d’opération impliquant un transfert de saumure. Enfin, une étude expérimentale et numérique portant sur la cinétique de dissolution du dioxyde de carbone dans la saumure a été menée. Celle-ci, bien qu’encore sujette à développement et principalement qualitative, confirme la nécessité d’intégrer un tel phénomène au modèle.

We present several new major features added to the Monte Carlo (MC) simulation code Brick-CFCMC for phase- and reaction equilibria calculations (https://gitlab.com/ETh_TU_Delft/Brick-CFCMC). The first one is thermodynamic integration for the computation of excess chemical potentials (μex). For this purpose, we implemented the computation of the ensemble average of the derivative of the potential energy with respect to the scaling factor for intermolecular interactions (⟨∂U∂λ⟩). Efficient bookkeeping is implemented so that the quantity ∂U∂λis updated after every MC trial move with negligible computational cost. We demonstrate the accuracy and reliability of the calculation of μexfor sodium chloride in water. Second, we implemented hybrid MC/MD translation and rotation trial moves to increase the efficiency of sampling of the configuration space. In these trial moves, short Molecular Dynamics (MD) trajectories are performed to collectively displace or rotate all molecules in the system. These trajectories are accepted or rejected based on the total energy drift. The efficiency of these trial moves can be tuned by changing the time step and the trajectory length. The new trial moves are demonstrated using MC simulations of a viscous fluid (deep eutectic solvent).

Density and speed of sound have been measured for pure components such as furan, 2-5-dimethylfuran (DMF), n-methyldiethanolamine (MDEA), diethylene glycol (DEG), triethylene glycol (TEG), and dimethylacetamide (DMA) using an Anton Paar (DSA-5000) vibrating U-tube densitometer in the temperature range of 278.15 to 343.15 K and ambient pressure (100 kPa). Density and speed of sound have been measured for furan + MDEA, furan + DEG, furan + TEG, and furan + DMA in the temperature range of 278.15 to 303.15 K, whereas for DMF + DMA, the temperature range is 283.15 to 343.15 K. Excess molar volume has been calculated for all binary systems. The Redlich–Kister model is used to correlate the experimental data. In order to identify the impact of molecular interactions participating significantly in the excess molar volume, the Prigogine–Flory–Patterson model is selected to correlate and predict the deviations for excess molar volumes of the binary mixtures.

Knowledge of the dissociation conditions of mixed-gas hydrate systems is of great importance for scientific understanding (e.g., clathrate hydrates in the outer solar system) and engineering applications (e.g., flow assurance, refrigeration, and separation processes). In this work, CO2+ O2hydrate dissociation points were measured at different O2mole fractions (11, 32, and 50%) using the isochoric pressure search method. The consistency of these new data was verified using the Clausius–Clapeyron relationship. The measurements performed for pressures up to 19 MPa overcome the lack of data for this system and also allow us to evaluate the model predictions from pure CO2hydrate to pure O2hydrate. To predict gas hydrate stability curves, in this work, the well-established hydrate theory of van der Waals and Platteeuw (vdWP) is combined with an electrolyte CPA-type equation of state (e-PR-CPA EoS), which has been successfully used to represent with high accuracy the fluid phase equilibria (including gas solubility and water content) of complex systems containing gas, water, and salt. The resulting model (e-PR-CPA + vdWP) was applied to the O2+ H2O and CO2+ H2O + (NaCl) systems by comparing with the literature data. In the studied temperature range (>270 K), the model predicts, as expected, a hydrate structure of type I for O2, CO2, and their mixtures. An excellent reproduction of the measured data by this complete model was obtained without any additional adjustable parameters.

Knowledge of the solubility of oxygen in natural water, which is generally saline, is important for several scientific and engineering fields. Applications such as geological storage of gas (containing O2, e.g., flue gas) or energy (compressed air energy storage) operate at high pressure. However, to date, there is no high-pressure O2solubility data in brine, which has led researchers to develop models to predict this important property. To overcome the lack of data, solubility of O2in brine has been measured using two different techniques, at molalities between 0.5 and 4 mol/kgw(NaCl), temperatures between 303 and 373 K, and pressures up to 36 MPa. In order to validate the experimental methods, measurements of the solubility of CO2in a highly concentrated brine (6 mol/kgwof NaCl) at temperatures between 303 and 373 K and pressures up to 39.5 MPa were performed also in this work. These measurements allowed the evaluation of existing models such as the well-known Geng and Duan model and the model recently developed by Zheng and Mao (ZM). The e-PR-CPA, Søreide–Whitson, and geochemical models used in our previous work were also used to process the new data. These last three models have been parameterized on measured and reported literature O2solubility data, and new optimized parameters of the ZM model have been proposed. These models reproduce the effect of temperature, pressure, and NaCl concentration on solubility with an average absolute deviation less than 5% from the measured data.

Many empirical models exist to describe the saturated vapor density. The majority of these models are detached from a physics basis, which often makes it difficult to select the most appropriate model for further thermodynamic modeling. Such empirical models are still used today because many equations of state do not describe vapor density well enough. The model presented here is based on a physical and a heuristic equation. It offers many advantages because it includes both the vapor pressure and the compressibility factor information for the saturated vapor line. In this manner, it is possible to describe the vapor density with one equation and only three parameters. The new model is independent of the compounds structure because it is based on vapor density measurements. It was tested in comparison to six frequently used models in terms of accuracy and thermodynamic consistency. The new model received the best rating and provides a useful tool for thermodynamic modeling and process design. The assessment of the models was based on Monte Carlo simulations and strict statistical methods for validating models. The new model can also be used in a cubic equation of state for the vapor pressure and vapor density correction.

Excess molar volumes for 1,4-dioxane + 2-propanol + 1,1,2,2-tetrachloroethane ternary mixture and for the constituent binaries were determined from density measurements over the entire composition range at four temperatures between 288.15 and 318.15 K and at atmospheric pressure. The ether-containing binary mixtures present a positive excess molar volume, VE, with alkanol and negative VEvalues with chloroalkane over the whole composition and working temperature ranges. As the temperature increases, the VEmagnitude increases for 1,4-dioxane + 2-propanol, whereas it decreases for 1,4-dioxane + 1,1,2,2-tetrachloroethane. For 2-propanol + 1,1,2,2-tetrachloroethane mixture, sigmoidal–VEcurves are observed and the VEincreases as the temperature increases. Sigmoidal–V123Ecurves are observed also for 1,4-dioxane + 2-propanol + 1,1,2,2-tetrachloroethane ternary mixture. The equations of Redlich–Kister and Cibulka were used to fit the experimental excess molar volume data, for the investigated binary and ternary mixtures, respectively. To provide more information on solute–solvent interactions, for the studied binary mixtures, the partial molar volumes and excess partial molar volumes are calculated over the entire composition range and at infinite dilution, at 288.15 and 318.15 K. The Prigogine–Flory–Patterson theory (PFP model) was applied to 1,1,2,2-tetrachloroethane-containing binary mixtures.