ePC-SAFT Equation Of State Research Articles

Viscosity of imidazolium ionic liquids and mixtures of ILs from entropy scaling using the PC-SAFT and ePC-SAFT equations of state

Entropy scaling is a promising method for the development of engineering models for transport properties of ionic liquids (ILs). Here we present two entropy scaling models for the viscosity of ionic liquids and their mixtures at various temperatures and pressures: 1) a molecular-based approach treating each IL as one pure species and using the PC-SAFT equation of state (EoS); and 2) treating each ion as a separate species and using the ePC-SAFT EoS. Both approaches were correlated to viscosity data of 12 ionic liquids from the imidazolium cation class and three different anions comprising 4233 data points with overall average absolute deviations (%AARDs) of less than 8 % over a wide range of temperature and pressures. The ion-based approach was better able to correlate IL viscosity at low temperatures and/or high pressure (to 4011 bar) than the molecular approach. The functional entropy-scaling coefficients for both models were regressed as linear functions of molecular weight, which allowed good prediction of another nine ionic liquids not in the training set. Interestingly, both approaches well predict the viscosity of binary mixtures of imidazolium ionic liquids. In addition, the effect of various reference viscosities and comparison with the Peng-Robinson EoS was performed.

Amino acid ionic liquids as components of aqueous biphasic systems for L-tryptophan extraction: Experiment and thermodynamic modeling with ePC-SAFT equation of state

Aqueous biphasic systems (ABSs) based on ionic liquids (ILs) have been considered as promising for the extraction, purification and separation of a wide range of substances, including biomolecules. Among the structurally modified ILs, amino acid ILs (AAILs) attract special attention.In this work we obtain systematic experimental data on the partitioning of L-tryptophan in the aqueous mixtures of 1-alkyl-3-methylimidazolium AAILs, [Cnmim]X, with different hydrocarbon chain length (n = 4, 8) and amino acid anions: X = [Leu] (L-Leucinate), [Val] (L-Valinate), [Lys] (L-Lysinate), and inorganic salt (K3PO4). Our results show that the partition coefficients are higher in the ABSs with AAILs than with halide ILs. AAIL with [C8mim]+ cation demonstrate a noticeable specificity of lysinate anions. The obtained new data are discussed in terms of AAIL’s structure. We conclude that hydrogen bonding is likely to play the major role in partitioning of the solute. Taking into account the low toxicity of AAILs, these ABSs have a high potential for the extraction of small biomolecules.Moreover, we found that in the studied ABSs based on chiral AAILs, partitioning of D-tryptophan is equal to that for L-tryptophan.ePC-SAFT is applied for the first time to model liquid-liquid equlibrium in ternary ABSs containing AAILs and partitioning of L-tryptophan. We obtain satisfactory results and conclude that ePC-SAFT is a promising tool for modeling ABSs that contain AAIL and inorganic salt.

Biocatalyst and continuous microfluidic reactor for an intensified production of n-butyl levulinate: Kinetic model assessment

The use of enzymes to catalyze chemical reactions has increased these recent years. Several models have been developed to express the kinetics over these biocatalysts. The most well-known of them, Michaelis-Menten, is used when only one substrate adsorbs on the enzyme. In the case of the esterification reaction, i.e., bimolecular system, a more complex kinetic model such as the Ping-Pong Bi-Bi should be applied. The use of such advanced models is essential for reactor scaleup and to optimize production. However, these models usually do not consider the reaction temperature. To fill this gap, a Ping-Pong Bi-Bi model was developed to produce butyl levulinate from the esterification of levulinic acid over an immobilized enzyme, Novozym®435. Microfluidic technology was used to ensure ideal mixing conditions. The Ping-Pong model, considering inhibition mechanisms, fits the experimental concentrations. ePC-SAFT equation of state was used to estimate the equilibrium constants.

Densities, Viscosities, and Thermal Conductivities of the Ionic Liquid 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium Acetate and Its Mixtures with Water

7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium acetate (mTBD acetate) is a protic ionic liquid that is being investigated for use in industrial processes, such as for producing textiles from cellulose. To aid in designing such processes, we have measured the densities, viscosities, and thermal conductivities of mTBD acetate and aqueous mixtures containing mTBD acetate. We also investigated how excess amounts of mTBD or acetic acid affect the density, and found that in general an excess of either component decreases the density. However, when no water is present, the sample with excess acetic acid actually has a slightly higher density than when there is an equimolar amount of acid and base. The maximum density occurs when some water is present (around 30–40 mol%). We also modeled the density data using the ePC-SAFT equation of state and provide simple correlations for calculating the viscosity and thermal conductivity of these mixtures.

A Comparative Study for Application of Pitzer and ePC-SAFT Equations to Predict Volumetric and Saturation Properties in “Formation” Water

Predictions of salt solubility, brine vapor pressure and density are necessary to plan subsurface and surface operations. In this work, a comparative study was conducted to investigate prediction capabilities for salt solubility, equilibrium and volumetric properties of several minerals in “Formation” water by the Pitzer model (a commonly used industrial model) and by the ePC-SAFT equation of state (EOS). To achieve this, several validation and comparison steps were considered for reliable implementation of both models. Firstly, solubility, brine densities and vapor pressures for single-salt solutions were predicted. Afterward, the models’ applications were extended to several mixtures of two salts to predict solubility compared to experimental data from available literature. ePC-SAFT shows promising accuracy. The average relative deviation for prediction of liquid density (which cannot be estimated with the Pitzer model) for single-salt solutions of NaBr, KCl, NaCl and Na2SO4 are 1.13%, 0.70%, 1.02% and 0.36%, respectively. The average relative deviation from experimental data of vapor pressure for mixtures of NaCl and KBr is 0.75% and for mixtures of NaBr and KCl is 0.74% for systems with different concentrations. Moreover, a stochastic regression procedure is presented to evaluate the ePC-SAFT parameters. This technique is used for strontium in different salt solutions. The average relative deviation for mean ionic activity coefficients calculated by ePC-SAFT from experimental data using the ePC-SAFT parameters of strontium from the work of Held et al. [1] for single-salt solutions of strontium chloride, strontium bromide, strontium iodide, strontium nitrate and strontium perchlorate are 19.73%, 19.96%, 15.15%, 14.95% and 25.70%, respectively. These values using the ePC-SAFT parameters of strontium regressed in this work are 6.98%, 10.13%, 8.33%, 9.59% and 10.08%, respectively. Finally, the solubility of different salts was studied for mixing of formation water (FW) and injection water (SW).

Competitive H2S – CO2 absorption in reactive aqueous methyldiethanolamine solution: Prediction with ePC-SAFT

Reactive absorption of CO2 and H2S in aqueous methyldiethanolamine (MDEA) solutions is considered within the ePC-SAFT equation of state. We demonstrate that ePC-SAFT can be employed in a predictive manner without regression of additional temperature-correlated terms. Mixed system predictions are tested using a consistent set experimental data covering a wide range of temperatures (313 K–413 K), partial pressures (0.001 kPa–1000 kPa), and MDEA mass fractions (0.05–wMDEA 0.75 wMDEA). Predicted partial pressures for acid gas absorption show good agreement for low MDEA fractions (wMDEA< 0.5). Absorption selectivity in binary H2S + CO2 absorption is correctly predicted, with absolute average deviations of 57.18% and 79.32% for partial pressures of CO2 and H2S. We identify a significant deterioration in ePC-SAFT predictive power for the high-MDEA regime (wMDEA > 0.5), likely originating from underlying assumptions in the Debye-Hückel electrolyte free energy treatment and representation of ionic species.

Measurement of infinite dilution partition coefficients of isomeric benzene derivatives in [bmim][Tf2N]-CO2 biphasic system and correlation with the ePC-SAFT equation of state

Infinite dilution partition coefficients of isomeric benzene derivatives in the [bmim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide)-CO2 biphasic system were measured with a supercritical fluid chromatography technique at pressures of 6–15 MPa and at temperatures of 313–353 K. The partition coefficients of o-cresol were always larger than those of m and p-cresol, while those of o-xylene were always smaller than those of m and p-xylene for all temperatures and pressures. The partition coefficients of the solutes in the ionic liquid-CO2 systems were found to be in the order of their vapor pressure in accordance with previous reports. The partition coefficient data were correlated with the ePC-SAFT (electrolytes perturbed-chain statistical associating fluid theory) equations and with the empirical LSER (Linear Solvation Energy Relationship)-δ model. The overall average relative deviation (ARD) of the ePC-SAFT equation using interaction parameters between ionic liquid and solute as fitting parameters was 8.2% and compared well with the LSER-δ model (7.5%). In one approach to improve the prediction capability of the ePC-SAFT equation, literature data of infinite dilution activity coefficients of toluene in the [bmim][Tf2N]-toluene biphasic system at atmospheric pressure were used to determine ePC-SAFT interaction parameters between [bmim][Tf2N] and toluene. Although this approach improved the ePC-SAFT description of the [bmim][Tf2N]–CO2–toluene system, the correlation was qualitative at high pressure and can be attributed to CO2 in the liquid phase that affects [bmim][Tf2N]-toluene interactions.

Separation factors for [amim]Cl–CO2 biphasic systems from high pressure density and partition coefficient measurements

Abstract In this work, densities and viscosities at atmospheric pressure and densities at high pressures of the ionic liquid, [amim]Cl (1-allyl-3-methylimidazolium chloride) were measured. The densities were evaluated by correlation with the Tait equation and the ePC-SAFT equation of state. Both relationships could describe the experimental density data over the full range of all temperatures (313–373 K) and pressures (0.1–200 MPa) within 0.007% and 0.053%, respectively. Infinite dilution partition coefficients, K w 3 ∞ , of fundamental benzene derivatives (chlorobenzene, bromobenzene, benzaldehyde and benzyl alcohol) between [amim]Cl and supercritical carbon dioxide were measured at 313–353 K and 6–21 MPa. The ePC-SAFT applied as a predictive model for the experimental partition coefficient gave high deviations (>900%). However, when the ePC-SAFT was applied as a correlative model, average deviation in K w 3 ∞ were 20%. A previously proposed semi-empirical LSER- δ model could correlate the K w 3 ∞ data to within 8.9%. Separation factors of solutes in [amim]Cl–CO 2 system were calculated with ePC-SAFT model and compared with literature results for [bmim]Cl–CO 2 since both of these ionic liquids have application to biomass processing. For each given ionic liquid, [amim]Cl and [bmim]Cl, the separation factors of non-polar or slightly polar compounds (chlorobenzene, bromobenzene and benzaldehyde) to the reference polar compound (benzyl alcohol) were always greater than 100, with [amim]Cl–CO 2 always having a higher separation factor than [bmim]Cl–CO 2 . Thus, [amim]Cl–CO 2 can probably provide better separation between non-polar and polar mixtures than [bmim]Cl–CO 2 .

Thermodynamic Properties of Aqueous Glucose–Urea–Salt Systems

In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl2), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum solutions, the osmotic coefficients were found to be in the range of 0.90–0.93. In a second step, the state of water in different glucose/salt/water and urea/salt/water systems was investigated. Depending on the kind of salt, the chemical potential of water in urea/salt/water is either higher or lower than in glucose/salt/water systems at equal nonelectrolyte concentrations. This result was found to be independent of the salt molality. Finally, the investigated systems were modeled with the Pitzer model and the ePC-SAFT equation of state, which allowed predicting of the properties of these multi-solute aqueous solutions.

Solubility of Pharmaceuticals and Their Salts As a Function of pH

In this work, the solubilities of lidocaine, thiabendazole, and terfenadine and their salts were measured and modeled as a function of pH. The aqueous solubilities of lidocaine and thiabendazole were measured in the pH range between 0.5 and 9.8 using hydrochloric acid or phosphoric acid. The solubility was modeled using the ePC-SAFT equation of state. The model parameters of the nonionized pharmaceuticals were determined from their solubilities in pure organic solvents (acetone, ethanol, 2-propanol, n-hexane, n-heptane, and toluene), which were also measured. Depending on the pH value, the ionization of the pharmaceutical and the identity of the pH-changing agent were considered during the modeling. The charge of the ionized pharmaceutical was explicitly taken into account. All other model parameters were deduced from those of the nonionized pharmaceutical. Furthermore, the precipitation of the pharmaceutical salt upon a pH change was described by its solubility product. The latter was fitted to one exper...

Measuring and modeling alcohol/salt systems

Liquid densities, osmotic coefficients, and mean ionic activity coefficients (MIAC) at 25°C of single-salt alcohol (methanol and ethanol) solutions containing univalent ions were measured and modeled with the ePC-SAFT equation of state. In accordance with our previous work [Held, C., Cameretti, L.F., Sadowski, G., Fluid Phase Equlilib. 270 (2008) 87–96], only two solvent-specific ion parameters were adjusted to experimental solution densities and osmotic coefficients: the solvated ion diameter and the dispersion-energy parameter. ePC-SAFT was able to reproduce experimental data of the respective alcohol/salt systems with reasonable accuracy. Based on the solvent-specific ion-parameter sets, it is possible to predict densities and MIACs in ternary and quaternary water/alcohol(s)/salt solutions by introducing appropriate mixing rules that do not contain any additional fitting parameters.