Fluid Phase Equilibria最新文献

Semiclathrate hydrates are water-based materials formed from aqueous solutions of ionic substances. To enhance the gas capture performance of these materials, it is necessary to direct focus on the cation, which is a key part of construction of the hydrogen-bonding framework. In this paper, we focus on the partly-asymmetric cations, i.e., the n-propyl, tri-n-butylammonium bromide (N3444Br) and tri-n‑butyl, n-pentylammonium bromide (N4445Br), which are yet to be subjected to gas hydrate formation. The three phase equilibrium (gas–hydrate–liquid) conditions for the systems of (N3444Br or N4445Br) + H₂O + (CH₄, CO₂ or N₂) in the range of the pressure and mass fractions of the aqueous solutions between 1 and 11 MPa and 0.10–0.40, respectively, are reported. In all the systems, the semiclathrate hydrates were successfully formed under gas pressure. It was demonstrated that both the N3444Br and N4445Br salts promoted hydrate formation under these gases, while in the case with lean aqueous solutions N3444Br acted as an inhibitor of methane hydrate formation in pure water system. The present data are compared with the literature data, and the effect of the side chain length on the phase behavior of the semiclathrate hydrate phase is discussed.

We probe the solvent effects on the preferential solvation of pharmaceutical species in mixed-solvent environments, identify its universal molecular-based signature, and characterize explicitly the macroscopic-to-microscopic formal connections between the thermodynamic non-idealities and the precisely defined fundamental structure making/breaking functions $S_{\alpha \beta }\left(T,P,x_{\alpha }\right)$. For that purpose, we link the thermodynamic response of the solute triggered by changes in the mixed-solvent environment to either a linear combination of $S_{\alpha \beta }\left(T,P,x_{\alpha }\right)$ or the universal preferential solvation function $PS\left(T,P,x_{\alpha }\right)$. Then, we illustrate the proposed approach by analyzing the solvation behavior of a series of pharmaceutical solutes in both aqueous-organic and mixed-organic environments at ambient state conditions. Moreover, we briefly discuss the tenets of a popular local composition-based model of preferential solvation, present a forensic analysis of the Kirkwood-Buff inversion expressions invoked in its implementation, and identify some pervasive modeling pitfalls as well as their associated common causes and concomitant consequences. Finally, we highlight the significance behind the analysis of preferential solvation phenomena, provide some pertinent observations on the findings, and offer a consistent outlook.

The possibility of hydrate formation poses a central issue for Carbon Capture and Storage (CCS) and Enhanced Oil Recovery with Water-Alternating-Gas (EOR/WAG) injection projects. In most of the cases, however, the available fluid for this purpose consists of a CO${}_2$-rich stream containing contaminants such as hydrocarbons and permanent gases. As a result, there is a growing interest in evaluating the effect of small impurities concentrations on the phase behaviour of such streams. This work investigates the impact of propane as a promoter in carbon dioxide hydrate formation, covering a concentration range in the feed gas phase between 10 and 69% on mole basis. The study also considers the L${}_w$-L${}_{{\mathrm{CO}}_2}$-H region, taking into account liquid and supercritical transportation commonly encountered in CCS projects. Additionally, a procedure to estimate uncertainties in the graphical determination of the dissociation temperature and pressure is discussed. The thermodynamic modelling approach includes three different modifications of cubic equations of state (CEoS): asymmetric mixing rule, advanced Huron-Vidal mixing rule, and cubic-plus-association approach. An alternative procedure based on setting different sets of CO${}_2$ Kihara’s parameters when shifting between structures was also used. While satisfactory average temperature deviations were obtained for those equations of state, maximum deviation between calculated and experimental temperatures spanned from 0.5 to 2.5 K, depending on the thermodynamic model.

Deep eutectic solvents (DESs) have appealed increasing research interest across various scientific and industrial applications, notably in relation to efforts in CO₂ capture. This study presents a novel series of DESs were synthesized on the basis of monoethanolamine (MEA) and N-methyldiethanolamine (MDEA) as hydrogen bond donors with tetrabutylammonium bromide (TBAB) and tetrabutylphosphine bromide (TBPB) salt as hydrogen bond acceptors. A gas solubility measurement experimental system based on pressure drop method has been established to evaluate the solubility of CO₂ in amine-based deep eutectic solvents. The evaluation was performed over a temperature range of 303.15 to 323.15 K and a pressure range of 100 to 1000 kPa. The results indicated that as the molar ratio of hydrogen bond donors increases, the solubility of CO₂ in DESs increases, while it was found to be less affected by the hydrogen bond acceptor. Of these, the solubility of CO₂ is strongest at a 1:10 molar ratio of TBAB and MEA. The nuclear magnetic resonance spectroscopy spectra (NMR) and FTIR spectroscopy revealed that the MEA-based DES mixture primarily exhibited chemical absorption of CO₂, while the MDEA-based DES predominantly showed physical dissolution of CO₂. In addition, it was observed that both temperature and pressure significantly influenced the CO₂ solubility, and a successful correlation was developed using different semi-empirical models.

In this research, the solubility of anticancer drugs in the supercritical CO₂ is modeled using the PC-SAFT equation of state (EoS). Ten anticancer drugs containing Empagliflozin, Sorafenib tosylate, Verapamil, Sodium valproate, Aprepitant, Sunitinib malate, Tamsulosin, Imatinib mesylate, Capecitabine, and Docetaxel are studied to evaluate the model performance. For each component, three temperature-independent model parameters are optimized by the experimental solubility data. The CO₂ is modeled as associative molecules with four associating sites and four association sites are considered on anticancer molecules. Therefore, the cross-association between anticancer and CO₂ molecules is considered. The average ARD, RMSE, and AAD values of the PC-SAFT EoS for the aforementioned anticancer drugs are obtained 11.45 %, 0.067, and 0.00026 %, respectively. The PC-SAFT EoS results are compared to various types of cubic EoSs and semi-empirical models. The results show that the PC-SAFT EoS with three model parameters can be used as a robust and efficient thermodynamic model to calculate the solubility of complex molecules in supercritical CO₂ up to high pressures and temperatures.

In recent years, the CO₂ super/transcritical power cycle has gained significant attention as the most widely studied power cycle. The accurate thermodynamic properties data is very important for cycle design and performance analysis. In this study, the Kiselev's crossover method based on the renormalization group theory is used to improve the classic SRK equation of state in non-critical region and reproduce the critical fluctuation phenomenon in critical region. The nonlinear equations method and interior-point method are used in the parameter fitting of crossover SRK (CSRK) to get the optimal parameters. The replaced method avoids the problem that Newton iteration method is prone to divergence and falling into local optima. The thermodynamic properties of CO₂ including the VLE properties, heat capacity and speed of sound are calculated by CSRK, respectively. The results show the calculation of the non-critical region is improved, and the critical fluctuation phenomenon in the near-critical region is described accurately, especially the second-order thermodynamic properties calculation results is improved from 3.65 % to 2.80 % compared with our previous work.

The purpose of this work is to provide consistent experimental measurements on the vapor–liquid equilibria (VLE) at the isobaric conditions of 50.00, 75.00 and 94.00 kPa, as well as experimental determinations of the liquid mass densities, the surface tensions and the dynamic viscosities at 298.15 K and 101.3 kPa of the methyl butyrate + tert-butanol binary system within the whole composition range. For these goals, a Gillespie-type cell is used to carry out the VLE measurements, whereas an oscillating densimeter, a maximum differential bubble pressure tensiometer, and a rotating viscometer are used to quantify the remaining physical properties. The thermodynamical quality of the reported VLE data is validated by Fredenslund’s consistency test. Based on the VLE results, this zeotropic binary mixture exhibits a positive deviation from Raoult’s law. Furthermore, the validated data are correlated with three activity coefficient models (i.e., Wilson, NRTL, and UNIQUAC), with the Wilson equation being the most accurate one. Excess volumes, surface tensions, and liquid viscosities data are correlated by Redlich–Kister-type expansions, and the Grunberg–Nissan equation is also applied to viscosity modeling. The calculated excess volumes display a positive deviation from the ideal solution model. Regarding surface tensions, this system showcases both negative and positive deviation, althouhg slight, from the linear behavior while exhibiting the linear trend at a molar fraction of methyl butyrate of 0.758. In addition, this bimodal deviation is adequately predicted by the Chunxi model with the Wilson parameters determined from the VLE data. Finally, the dynamic viscosities data obey a strictly monotonic mole dependence predicted by Eyring’s theory, although without high accuracy. These results also reflect some interesting phenomena related to competitive association effects, which are discussed.

The Mercedes Benz (MB) model of water is quite popular for explaining the properties of water, but the complete phase diagram has not yet been published. In the MB model, water molecules are modelled as two-dimensional Lennard-Jones discs, with three orientation-dependent hydrogen-bonding arms arranged as in the MB logo. Nested Sampling (NS) is a powerful sampling algorithm for the parameter space that directly calculates the partition function. NS can be used for sampling the equilibrium thermodynamics of atomistic systems and allows access to all thermodynamic quantities in absolute terms, including absolute free energies and absolute entropies. Here, NS is used to calculate the phase diagram of the simple two-dimensional Mercedes-Benz (MB) model of water. 32 water particles were used in NS. While this number of particles provides sufficient agreement with the simulations, the results from fewer particles slowly begin to diverge from the result from NS with 32 particles as some of the equilibrium lines begin to shift. By combining the results from NS and molecular dynamics (MD) simulations, different phases were located and identified. In total, 5 different solid phases, 3 liquid phases and one gaseous phase were observed.

New thermodynamic correlations were proposed for the solubility of pharmaceutical compounds in supercritical carbon dioxide based on the solid-liquid equilibrium model. The activity coefficient models proposed in the study were based on Universal quasi-chemical Functional Group Activity Coefficient and Wilson models. The pharmaceutical drug compounds used in this study belong to anticancer, antibiotics, anti-androgenic, non-steroidal anti-inflammatory drugs, anti-prostatic tumour drugs and antiemetic drugs. The correlating ability of the proposed models was discussed in terms of various statistical parameters. Further, the proposed model results were compared with six existing solid-fluid equilibrium model results. It was found that the newly proposed models were more promising than those of existing solid-fluid equilibrium models. The correlating ability of the proposed models was discussed in terms of various statistical parameters.

Salts composed of the cholinium cation (such as choline hydroxide and choline chloride) have become one of the main reactants for the synthesis of greener ionic liquids, but, for a proper description of the aqueous solutions of these strong electrolytes by thermodynamic modelling, reliable data on liquid density $\left(\rho \right)$ and vapour pressure $\left(p\right)$ are needed, which are often unavailable. So, in this work, the liquid density $\left(\rho \right)$ of binary aqueous solutions of choline bicarbonate ([Ch][Bic]), choline (2R,3R)-bitartrate ([Ch][Bit]), choline chloride ([Ch]Cl), choline dihydrogen citrate ([Ch][H₂Cit]) and choline hydroxide ([Ch]OH) were measured at 298.15 or 313.15 K and 0.1 MPa and correlated using second-degree polynomials with salt molality $\left(m\right)$, obtaining determination coefficients $\left(R^2\right)$ higher than 0.9974. Furthermore, the osmotic coefficients $\left(\varphi \right)$ of these binaries were determined using vapour pressure osmometry (VPO), at 313.15 K and 0.1 MPa, being satisfactorily described by the Extended Pitzer Model of Archer, which yielded low values of standard deviation $(3.58<{\sigma }_{\varphi }·{10}^3<12.86)$. Then, the mean molal activity coefficients $\left({\gamma }_{\pm }\right)$ and excess Gibbs free energies $\left(G^E/RT\right)$ were calculated, following the order [Ch][H₂Cit] > [Ch][Bit] > [Ch][Bic] > [Ch]OH > [Ch]Cl, which corresponds to the decreasing polarity of the choline salts and agrees with the empirical law of matching water affinities (LMWA).