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Computer-aided molecular design (CAMD) has attracted much attention in the past 30 years. The generation of a candidate molecular structure satisfying a set of structural constraints is an important part of such a problem. However, the commonly used structural constraints proposed by Odele and Macchietto [Odele, O.; Macchietto, S. Computer Aided Molecular Design: A Novel Method for Optimal Solvent Selection. Fluid Phase Equilib. 1993, 82, 47], cannot provide sufficient and necessary conditions for generating cyclic molecules. In this paper, the sufficient and necessary conditions for molecular generation were presented. According to these conditions, some modifications of the conventional constraints were made, and mathematical proofs demonstrated that the modified constraints can perfectly generate structurally feasible molecules with no more than two rings. Moreover, some new constraints were proposed to help generate feasible aromatic molecules with less than two rings. Finally, several cases were presented to validate the correctness and applicability of the proposed modifications via comparing the results of the CAMD problems using the constraints before and after modification, and the new constraints were applied to design solvents for liquid-liquid extraction. It is shown that the modifications presented in this paper can improve the reliability of results of CAMD, and additionally, the conditions of molecular generation proposed in this paper can be easily used to derive structural constraints for any type of target molecules. [ABSTRACT FROM AUTHOR]

Stripping crystallization (SC) was used to purify styrene (ST) from a liquid mixture of ST and ethylbenzene (EB). This new separation technology combines vaporization and crystallization to yield a crystalline product and a vaporous mixture from a liquid feed via three-phase equilibrium transformations. The three-phase equilibrium conditions for a liquid mixture determined by the thermodynamic calculations were adopted to direct the SC experiments. A unique apparatus was designed for SC experiments at low temperatures and pressures for a series of three-phase equilibrium conditions (from -33 °C and 9.0 Pa to -80 °C and 0.03 Pa). The experiments indicate that SC can be applied to the purification of ST from a liquid mixture of ST and EB with an initial ST concentration of 0.80-0.95. [ABSTRACT FROM AUTHOR]

Natural gas and oil produced from shale accounts for a significant portion in the global production. Because of the large surface area and high organic content in shale formations, adsorption plays a major role in the storage of the hydrocarbons within the rock and their phase equilibrium. This study provides a comparison of several engineering models for gas adsorption in shale based on the recent literature data for pure and binary gases. For pure components, Langmuir, the modified Toth-Langmuir, and the Multicomponent Potential Theory of Adsorption using Dubinin-Radushkevich potential (MPTA+DRA) were compared. The three models show similar deviations lower than 10%. For binary gases, Multicomponent Langmuir (ML), Ideal Adsorbed Solution Theory (IAST), and MPTA were evaluated, where MPTA shows the lowest deviation with 17.9%. Additionally, we presented an analysis of the phase envelope shift under the influence of the capillary pressure and the adsorption film. ML and IAST were used to calculate the adsorption amount, whereas MPTA was used to generate artificial adsorption data over a large temperature range and for other homologous hydrocarbons to estimate the ML and IAST parameters. The adsorption film thickness was considered in the calculation of the effective capillary radius and the corresponding capillary pressure. The combined effects modify the saturation pressure in the whole temperature range except at the critical point. The biggest impact was found on the bubble point branch away from the critical point where the interfacial tension of the system is more pronounced. [ABSTRACT FROM AUTHOR]

The perturbed-chain SAFT (PC-SAFT) equation of state (EOS) is a very popular and promising model for fluids. Resolution of the PC-SAFT EOS is generally conducted by subroutine-based calculations that involve logical conditions. This approach can lead to nonsmoothness and convergence issues when used with gradient-based solvers in an equation-oriented (EO) framework. In this paper, we propose a novel EO approach for the PC-SAFT EOS embedded in large flowsheet optimization. First, the mathematical structure of the PC-SAFT EOS is analyzed through a digraph. It reveals that for polymerization systems, resolution of the PC-SAFT EOS is coupled not only by phase equilibrium but also by the polymerization kinetics. This feature strongly motivates implementation of both EOS resolution and process optimization in a complete EO framework. A novel EO approach is proposed for selecting the appropriate root of the PC-SAFT EOS by incorporating thermal stability criteria to eliminate the undesirable roots. Numerical examples in simulation and optimization of flash drums are presented to demonstrate that the proposed EO formulation can always select the appropriate root. Finally, the EO formulation is applied for simulation and optimization of an industrial polymerization process. The results show advantages of the proposed EO method compared to traditional sequential modular-based simulation software in terms of computational robustness and efficiency. [ABSTRACT FROM AUTHOR]

Double retrograde vaporization is a phase behavior phenomenon that occurs close to the critical point of binary mixtures and characterized by wide relative difference of volatility between its components. In general, the phenomenon occurs in a very narrow composition range, making the prediction of the molar fraction and pressure of the phase equilibrium problem a challenging problem. Here we employ sophisticated modern numerical methodology to untangle the geometry of this complex phenomenon, based on the robust methodology of inversion of functions. The objective of this work is to evaluate the system that describes the phenomenon close to the singularity points of the problem, especially with respect to the degeneration of solutions. The method used offers an effective framework for the qualitative analysis of systems of nonlinear equations. We study an application of this methodology in the binary system formed by ethane + limonene, at three different configurations (four dew points, three dew points and only one dew point). The results indicate a very complex structure of the function in the neighborhood of the phenomenon. [ABSTRACT FROM AUTHOR]

Vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), and vapor-liquid-liquid equilibria (VLLE) for systems involving highly nonideal components, namely, water, alcohols, alkanes, ketones, aldehydes, esters, and ethers, were investigated to evaluate the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS) and two widely used activity coefficient models, that is, the universal quasichemical (UNIQUAC) and UNIQUAC functional-group activity coefficients (UNIFAC). Parameters used for the PC-SAFT EOS were taken from literature or estimated in this work, while those for UNIQUAC and UNIFAC were from commercial process simulator Aspen plus 8.4. It was found that all the three models yield reliable correlations/predictions for VLE calculations. However, UNIQUAC and UNIFAC were observed to be unreliable for LLE and VLLE calculations despite successful reproductions of experimental data in some cases. The calculated results deviate significantly from experimental data in many cases. Particularly, both models predict artificial liquid-liquid phase splitting for a number of miscible mixtures. Nonetheless, PC-SAFT EOS with the use of a single set of parameters reproduces experimental data quantitatively in most cases and provides reasonably accurate results in all other cases. This remarkable performance of PC-SAFT EOS potentially eliminates the need for various thermodynamic models and consequently the need for selecting a thermodynamic model when performing phase equilibria calculations using commercial software. This is important for practitioners, since (1) it remains unclear to select an appropriate model from the available models of a process simulator or thermodynamic package for a given phase equilibria calculation despite the presence of some type of rule of thumb and (2) it is also likely that none of the existing models is sufficiently accurate. In addition, it was shown that both pure-component parameters and binary interaction parameters for the PC-SAFT EOS are well-behaved for a homologous series, which allows for parametrization for weakly characterized components by interpolation or extrapolation, and consequently, facilitates the development of a practical tool for phase equilibria calculations. [ABSTRACT FROM AUTHOR]

Modified Separation of Cohesive Energy Density (MOSCED) is an attractive method for modeling phase-equilibria because it both can make quantitative predictions and give insight into the system's underlying molecular-level interactions. While MOSCED predicts satisfactory values of limiting activity coefficients of organics in water, we find that predicted limiting activity coefficients for water (here the solute) in organic solvents shows a much greater disparity with reference data. Moreover, the error is systematic and increases as the value of the limiting activity coefficient increases. After detailed assessment of the MOSCED parameters for water, we find this is not a limitation of the model but results from how the parameters were regressed. As a consequence, in the present study we reregress MOSCED parameters for water which greatly improves the accuracy with which MOSCED may predict limiting activity coefficients of water in organic solvents, with the average absolute error decreasing from 3056.2% to 63.2%. The improvement is systematic, increasing as the value of the limiting activity coefficient increases. We additionally demonstrate the ability of the revised parameters to make improved binary liquid-liquid equilibrium calculations in aqueous systems. [ABSTRACT FROM AUTHOR]

An enterprise database of pure ionic liquids (ILs) for its use in the Aspen ONE programs is presented. The database is identified as ILUAM, and the first version (ILUAM01) contains 100 ILs composed of 30 cations and 23 anions. The IL components were introduced in Aspen Properties as pseudocomponents using information from the computational COSMO-RS method and from experimental viscosity data. ILUAM database was created to be used along with the COSMOSAC property model implemented in Aspen Plus, allowing evaluating IL process performance without needing further experimental data. Some validation tests were carried out to demonstrate the successful incorporation of ILs in the Aspen Plus property system. Then, the performance of ILUAM01 database in thermodynamic property predictions of mixtures involving ILs and conventional chemical compounds was revised in terms of activity coefficients at infinite dilution and phase equilibrium data. The property description of pure ILs and IL mixtures with conventional chemical compounds using COSMO-based/Aspen Plus approach was found with the accuracy level required in the conceptual design of new processes. ILUAM database offers the opportunity of performing systematic evaluation of potential industrial applications of ILs and their competitiveness as alternative to conventional solvents. [ABSTRACT FROM AUTHOR]

One of the major challenges of an equation of state lies in the description of water and aqueous systems. Its abundance and unique properties turn water into one of the most important molecules in the industry. However, because of these peculiar characteristics, its modeling is far more complex than for any other common solvent. In this work, a modified cubic plus association (CPA) model, which includes the correct description of the pure component critical temperature and critical pressure, is expanded to water and its systems. A brief analysis of the predicted water purity properties is conducted, comparing those to a previous version of the model. Results for a group of binary systems, including liquid-liquid equilibria with alkanes and alcohols, highlighting their minima in aqueous solubility, and gas solubility in water/water solubility in gas, are also presented. Finally, ternary and multicomponent systems of water + hydrocarbons and water + polar compound + hydrocarbons are also modeled and discussed. [ABSTRACT FROM AUTHOR]

A robust and efficient algorithm for simultaneous chemical and phase equilibrium calculations is proposed. It combines two individual nonstoichiometric solving procedures: a nested-loop method with successive substitution for the first steps and final convergence with the second-order modified RAND method. The modified RAND extends the classical RAND method from single-phase chemical reaction equilibrium of ideal systems to multiphase chemical equilibrium of nonideal systems. All components in all phases are treated in the same manner and the system Gibbs energy can be used to monitor convergence. This is the first time that modified RAND was applied to multiphase chemical equilibrium systems. The combined algorithm was tested using nine examples covering vapor-liquid (VLE) and vapor-liquid-liquid equilibria (VLLE) of ideal and nonideal reaction systems. Successive substitution provided good initial estimates for the accelerated computation with modified RAND, to ultimately converge to the equilibrium solution without failure. [ABSTRACT FROM AUTHOR]

To describe the behavior of real liquid mixtures, binary interaction parameters of component-based models like, e.g., UNIQUAC, are fitted to experimental data or estimated values from group contribution (GC) methods like UNIFAC and mod. UNIFAC. Because parameters of GC methods are based on a large number of data sets for many similar mixtures, they are typically less precise than models fitted directly to individual data sets for the binary mixture of interest. In some cases, however, it was reported that UNIFAC with group parameters independently regressed to the same data sets represents binary mixtures more accurately than UNIQUAC, which could be due to better localization of interactions. This possible advantage was analyzed using over 3700 data sets from the Dortmund Data Bank. Advantages and disadvantages of the group-based approach are identified, which could be well-explained by the change in concentration base; the results should also hold for segment-based models like NRTL-SAC and COSMO-RS. [ABSTRACT FROM AUTHOR]

Modeling the vapor liquid phase equilibrium of mixed refrigerants is the essential precondition for the calculation of refrigeration system. In this work, the study on 48 pure substances and 58 binary systems consisting of CxHy and CxHyFz was performed. Both Peng-Robinson (PR) and perturbed-chain SAFT (PCSAFT) were investigated. The relationship between the parameters in PR and PCSAFT was exhibited. Strong linear function of the volume parameter mσ3 in PCSAFT with covolume parameter b in PR were found, as well as the energy parameter m2 in PCSAFT with energy parameter a/b in PR. This correlated characteristic provides an idea for regressing pure substance parameters and a criterion whether the regressed parameters are reasonable or not. The interaction parameters in PR-VDW and PCSAFT show consistent tendency, and both are limited to a very narrow range. The simple predictive method was proposed by using the average value 0.146 for PR-VDW and 0.093 for PCSAFT. The internal correlated behaviors result that the PCSAFT equation is no better than PR equation on the VLE description of CxHy + CxHyFz systems. [ABSTRACT FROM AUTHOR]

Partially water-soluble monomers achieve phase equilibrium between aqueous and dispersed phases, and the interphase mass transfer plays a significant role in suspension polymerization. This work developed a computational fluid dynamics model to simulate the liquid-liquid suspension polymerization process. Complex multiphase flow behaviors and multiscale polymer properties were simultaneously simulated using the combination of an Eulerian-Eulerian two-phase flow model, an atom transfer radical polymerization kinetics model, a population balance model (PBM), and an interphase transfer model. The simulation results for monomer conversion, molecular weight (M n), polydispersity index (PDI), and Sauter mean diameter (d 32) agreed well with the experimental data, thereby validating the soundness of the multiscale model. The proposed model was then employed to predict key variables of the polymerization system. The coupled model can benefit the optimization and scale-up of suspension polymerization reactors with such multiscale characteristics. [ABSTRACT FROM AUTHOR]

The Transferable Anisotropic Mie potential (TAMie) is extended to ketones, aldehyhdes, and small cyclic alkanes. Parameters defining the Mie pair potential, representing van der Waals interactions, as well as partial point charges were treated as adjustable. These adjustable parameters were identified by minimizing deviation of calculated vapor pressure data and liquid density data to experimental data. The optimization procedure was supported by an analytic equation of state, according to Hemmen and Gross. The optimal point charges for aldehydes and ketones were found by varying them along a predefined grid of values. Results for phase equilibria of pure substances show good agreement with experimental data. The absolute average deviations for aldehydes and ketones in the reduced temperature range TR = T/Texpcrit = 0.55-0.96 are lower than 3.4%. For cyclohexane and cyclopentane the deviations are 0.6%. [ABSTRACT FROM AUTHOR]

The separation of ethylene glycol (EG) and 1,2-butanediol (1,2-BDO) azeotrope is a key technical problem in the synthesis process of EG via dimethyl oxalate (DMO) from syngas. On the basis of systematic investigation, aldolization is expected to be the solution to this industrial problem. Thus, the essential thermodynamics data were determined and correlated well by the corresponding thermodynamic equation, including the vapor pressure of 2-methyl-1,3-dioxolane (2MD) and 4-ethyl-2-methyl-1,3-dioxolane (4EMD), vapor-liquid equilibrium (VLE) data of binary mixture 2MD-4EMD at 101.3 kPa, and liquid-liquid equilibrium (LLE) data of binary system 4EMD-water at atmospheric conditions. The vapor-liquid-liquid equilibrium (VLLE) of binary system 4EMD-water has been successful predicted by LLE experimental data. Finally, the thermodynamics parameters were provided as a reference to design a separation process of the EG and 1,2-BDO mixture. The simulation and optimization results indicate that EG and 1,2-BDO could been separated effectively, which presents the potential of applying aldolization in synthesis of EG basic coal. [ABSTRACT FROM AUTHOR]

The deposition of asphaltenes in porous media is one of the most difficult problems during CO2 flooding. In this paper, the adsorption of asphaltenes onto Al2O3 nanoparticles was studied through two methods: (i) by adding a certain mass of nanoparticles in a fixed volume of solution with different initial concentrations of asphaltenes and (ii) by exposing a certain amount of asphaltenes in a fixed volume of solution to different nanoparticles additions. Then, the impact of Al2O3 nanoparticles on the asphaltene precipitation was investigated using the IFT behavior of the oil-CO2 system. Coreflood tests were conducted to study the potential of nanoparticles for inhibition of asphaltenes damage during CO2 flooding, and the effect of injection parameters of nanofluid. It is found that the solid-liquid equilibrium (SLE) can well describe the isotherms of asphaltene adsorption. The trend of the IFT-pressure curve is affected by asphaltene accumulation at the oil-CO2 interface. The slopes in the high pressure region can be used to examine the intensity of asphaltene precipitation. As the addition of nanoparticles increases, the IFT slope in the high pressure range decreases. This is because the asphaltenes are absorbed at the surface of nanoparticles. As a result, the nanoparticles prevent asphaltene precipitation from accumulating at the CO2-oil interface, hence causing asphaltene to remain within the bulk of oil. The higher the mass fraction of Al2O3 nanoparticles is, the lower the intensity of the asphaltene precipitation would be. The coreflood results show that the injection of Al2O3 nanofluid can lessen the oil permeability reduction because the nanoparticles can inhibit the deposition of asphaltenes onto the sand surfaces in the porous media. The 0.5 wt % nanoparticles and the 0.1 nanofluid/CO2 slug volume ratio are considered as the optimum for inhibiting asphaltenes damage during CO2 flooding. Continuous CO2 and nanofluid injection could be more effective compared with the cyclic injection pattern. [ABSTRACT FROM AUTHOR]

Confined fluids such as oil and gas mixtures inside tight reservoirs are systems that can experience high capillary pressure difference between the liquid and gas phases. This capillary pressure difference has an effect on the phase equilibrium and in some cases is considerably high. We presented an algorithm which can reliably compute the whole phase envelope for multicomponent mixtures when there is a capillary pressure difference. It uses an equation of state for the phase equilibrium and the Young-Laplace equation for the capillary pressure model. The algorithm proves to be robust and efficient for test mixtures with wide ranges of compositions at different capillary radii and vapor fractions. The calculation results show that the phase envelope changes everywhere except at the critical point. The bubble point and the lower branch of the dew point show a decrease in the saturation pressure, whereas the upper branch of the dew point shows an increase. The cricondentherm is shifted to a higher temperature. We also presented a mathematical analysis of the phase envelope shift due to capillary pressure based on linear approximations. The resulting linear approximation equations can predict the correct direction of the phase envelope shift. Combined with the multicomponent Clapeyron equation, the equations reveal why the shift changes direction for the saturation pressure at the cricondentherm and for the saturation temperature at the cricondenbar. The equations can be used to estimate the magnitude of shift, and the approximation is close for the change in the bubble point pressure. [ABSTRACT FROM AUTHOR]

In this work, ionic liquids (ILs) are proposed as candidates for extractive removal of 2-phenylethanol (PEA) (well-known rose-like aroma compound) from its aqueous solutions. Four ILs based on different cations, namely, 1-hexyl-1-methylpyrrolidinium, 1-hexyl-1,4-diaza [2.2.2]bicyclooctanium, 1-(2-methoxyethyl)-3-methylimidazolium, and 1-(2-methoxyethyl)-1-methylpyrrolidinium, and bis(trifluoromethylsulfonyl)imide anion were under study. Thermodynamic data at ambient pressure are presented for pure ILs (including temperature-dependent density data and thermal characterization with DSC) as well as for binary systems {IL + water} and ternary systems {IL + PEA + water}. For the binary systems, (liquid + liquid) equilibrium phase diagrams were determined in temperature range T = (280-370) K. For ternary systems, (liquid + liquid) equilibrium was investigated at T = 308.15 K. An impact of the cation structure on the studied properties is established. The data obtained are discussed in terms of the selectivity and distribution ratio of separation of PEA from water. Modeling of the measured properties with two modern chemical engineering thermodynamic tools, namely, nonrandom two liquid (NRTL) model and perturbed-chain statistical associating fluid theory (PC-SAFT), is demonstrated. The NRTL model is applied in a purely correlative fashion in the case of both binary and ternary systems. In turn, the predictive capacity of the PC-SAFT is tested for ternary (liquid + liquid) equilibrium using the combining rules corrections transferred from binary data. [ABSTRACT FROM AUTHOR]

It is of great engineering significance to find an accurate model to predict CO2 freezing and avoid plugging in the light hydrocarbon separation process of natural gas. Research starts from CO2 freezing in simple CH4-CO2 binary systems. By use of a traditional model based on the Antoine equation, the calculated freezing temperature in liquid-solid equilibrium (LSE) is not as accurate as that in vapor-solid equilibrium (VSE). Then a new thermodynamic method of reference state of hypothetical fluid is used to replace LSE model based on the Antoine equation to calculate solid CO2 fugacity. The improved phase-equilibrium model based on GERG-2008 is proved to be the most accurate one to calculate CO2 freezing temperature, in which the Antoine equation is used in VSE model while reference state method is used in LSE model. Compared with experimental data, the calculated results also show a higher accuracy in complex natural gas system. Besides, the improved phase-equilibrium model is applied in the actual light hydrocarbon separation process to research the CO2 freezing phenomenon, which explains wide applicability of the new model. [ABSTRACT FROM AUTHOR]

The phase behavior of the methanol-palm oil system was first experimentally assessed in the temperature range of 363-393 K and pressure range of 1-4 MPa. Second, comparative modeling of the phase equilibrium of the methanol-tripalmitin system was performed using the Peng-Robinson equation of state (PR EoS) with second-order modified Huron-Vidal (MHV2) mixing rules, in combination with the universal functional activity coefficient model (UNIFAC) and the universal quasi-chemical (UNIQUAC) excess Gibbs free-energy model. The agreement between experimental and modeling results was found to be satisfactory when MHV2 mixing rules are used in combination with the UNIQUAC model. Finally, the thermodynamic model was applied to predict fluid phase equilibria of palm oil transesterification with supercritical methanol. From the isochoric method in the temperature range of 373-693 K and the pressure range of 1-16 MPa, the model was found to predict global mixture behavior. [ABSTRACT FROM AUTHOR]

A new process for the production of glycine by using antisolvent crystallization with the mixture of ethylene glycol (MEG) and water as a substitute for methanol has been developed on the basis of chemical modeling phase equilibria for the glycine-NH4Cl-MEG-H2O system. MEG is considered as a green solvent because it has great higher boiling point up to 470 K and thus is almost nonvolatile compared with methanol. We discovered that the solubility of glycine, NH4Cl and their mixtures can be greatly changed by altering the composition of the mixed MEG-H2O solvents and realized the complete separation of glycine and NH4Cl by water evaporation. Phase equilibria for the glycine-NH4Cl-MEG-H2O system were measured from 278 to 353 K. The mixed-solvent electrolyte (MSE) model was applied with new binary interaction parameters obtained from regressing experimental and literature data. This newly modified model accurately predicted the solubilities in the quaternary glycine-NH4Cl-MEG-H2O system with average absolute relative deviations of 5.84% and 1.03% for glycine and NH4Cl, respectively. Simulation for the new process was performed by the model to investigate its operating conditions, from which the optimal composition of antisolvent was determined to be 50 wt % of MEG solution. Under this condition, glycine and NH4Cl were successfully separated from their solid mixtures in batch crystallization experiments, validating the feasibility of the proposed process for glycine production. [ABSTRACT FROM AUTHOR]

Integrated phase partition, online phase identification, and phase-based monitoring methods are proposed for multiphase batch processes with uneven durations. A new phase partition method is developed based on the warped K-means (WKM) clustering algorithm, which divides the entire batch into several operation phases by clustering the trajectory data of phase-sensitive process variables. This WKM-based phase partition method can efficiently cope with the sequentiality of batch data and, thus, ensures a reasonable phase partition result. Besides, because only phase-sensitive variables are used for phase partition, the phase partition accuracy is improved. An online phase identification method is proposed to identify the corresponding operation phase of a new sample according to a phase identification combination index (PICI). PICI quantifies the correlation of a new sample with each operation phase by calculating distance and time difference between the sample and the phase center. The PARAFAC2 and unfolded principal component analysis (uPCA) methods are applied to build monitoring models from the uneven-length batch data in each phase. T2 and SPE statistics are constructed for fault detection. The contribution plot of T2 statistic is used for fault diagnosis. The effectiveness and advantages of proposed methods are illustrated by the case study in a fed-batch penicillin fermentation process. [ABSTRACT FROM AUTHOR]

Because of the effect of nanoscale confinement, the phase behavior of fluids confined in nanopores differs significantly from that observed in a PVT cell. In this paper, the cubic Peng-Robinson equation of state (EOS) is coupled with capillary pressure equation and adsorption theory to investigate and represent the phase equilibria of pure components and their mixtures in cylindrical nanopores. The shift of critical properties is also taken into account. Because of the effect of an adsorption film, an improved Young-Laplace equation is adopted to simulate capillarity instead of the conventional equation. For the adsorption behavior, the experimental data of the adsorbent of silicalite are used to represent the adsorption behavior of hydrocarbons in nanopores. Then a prediction process for the behavior of methane, n-butane, n-pentane, n-hexane and their mixtures are performed. Furthermore, the results are compared against the available experimental data to validate the accuracy of this scheme. An actual Eagle Ford oil is also used to examine the performance of our scheme. Results indicate that the presence of an adsorption film can further increase the vapor-liquid equilibrium constant (K-value) and capillary pressure of the confined pure-component fluid, especially in the nanopores with a few nanometers. The smaller the nanopore radius, the higher the deviation between the actual K-value and the estimated value. The capillary pressure presents a bilinear relationship with the pore radius in a log-log plot. For a binary mixture, it is observed the higher the difference between the two components, the stronger the nanopore confinement effects. For a multicomponent mixture and the real Eagle Ford oil, as the pore radius reduces, the bubble point pressure is depressed and the dew point pressure is increased. When the adsorption film is neglected, the bubble point pressure is overestimated, and the dew point pressure is underestimated. For the Eagle Ford oil, when the nanopore radius is higher than about 100 nm, the behavior approaches the bulk value and the influence of nanopore confinement can be neglected. The depression of bubble point pressure of an Eagle Ford oil reservoir well explains the behavior of a long-lasting flat producing gas/oil ratio (GOR). The phase behavior of tight oil plays an important role in reserve evaluation and development process of tight oil reservoirs. This study will shed some important insights on the phase behavior of tight oil in nanopores. [ABSTRACT FROM AUTHOR]

This paper reports the thermodynamicinhibition effect of sevenionic liquids (ILs) on methane hydrate formation. The isochoric multistepheating dissociation pressure search method is applied for experimentallydetermining the phase boundary between hydrate–liquid–vapor(H–L–V) phases and liquid–vapor (L–V)phases in the pressure and temperature ranges of 3.45–13.28MPa and 274.3–287.6 K, respectively. All the studied IL aqueoussolutions are used at a mass fraction of 0.1. A comparison of thethermodynamic inhibitory performance of various ILs is carried outand reveals the predominant role of the type of anion of ILs. Consideringthe difficulty in directly measuring the dissociation enthalpies,the values of ΔHof methane hydrate are alsocalculated using the Clausius–Clapeyron equation. It is foundthat the mean dissociation enthalpies of methane hydrate in the presenceof the seven ILs vary from 59.05 to 60.81 kJ·mol–1, and are very close to that in pure water. [ABSTRACT FROM AUTHOR]

The E-PPR78 model is a predictive version of the widely usedPeng–Robinson equation of state in which the binary interactionparameters are estimated by a group-contribution method. With the24 groups available before the writing of this paper, such a modelcould be used to predict fluid phase equilibrium of systems containinghydrocarbons, permanent gases (CO2, N2, H2S, H2, CO, He, and Ar), mercaptans, alkenes, andwater. During the process of the Carbon dioxide Capture and Storage(CCS), it is often necessary to know thermodynamic properties of mixturescontaining carbon dioxide, water, hydrocarbons, and trace gases, suchas nitrogen, argon, hydrogen, carbon monoxide, sulfur dioxide, oxygen,or nitric oxide. Basically, except sulfur dioxide, oxygen, and nitricoxide, most components encountered in systems regarding CCS processescould be modeled with the E-PPR78 model. So in orderto predict the phase behavior and estimate energetic properties (e.g.,enthalpy or heat capacity changes on mixing) of such systems, theapplicability range of the E-PPR78 model is extendedthrough the addition of three new groups: “SO2,”“O2,” and “NO.” [ABSTRACT FROM AUTHOR]

We present a group contribution pseudocomponent(PC) method formixtures of petroleum fluids and a solvent based on the characterizationmethod (CM) for petroleum fractions and the predictive Peng–Robinson1978 (PPR78) model. The objective of this study is to model the phaseequilibrium of crude oil and a solvent consisting of one or multiplepure components. We develop a structural analysis of crude oil tobridge the CM and the PPR78 model, which predicts the temperature-dependentbinary interaction parameters (BIP) among the PCs and pure components.The predicted results using our method agree well with experimentaldata for mixtures of oil sand bitumen and propane, CO2,or water. The approach is applicable to phase equilibrium predictionsof mixtures of crude oil and water over a wide range of temperatures(273–644 K or higher as reasonable extrapolations) and pressures(4 kPa–26 MPa). [ABSTRACT FROM AUTHOR]

Theinterfacial properties and interactions between phosphatidylcholine(PC) vesicles and surfaces (air/water, oil/water, or oil/ethanol)were investigated with regard to the stability of the dispersed systems.Understanding interactions between the PC vesicles and different solutionsis very important to make it easier to recognize various physiologicalfunctions of membranes. The interactions and possibility of creatingstable PC-based systems were studied by different techniques, suchas surface tension, microelectrophoresis, and static and dynamic lightscattering measurements. Besides determining the physicochemical characteristics,another aim of this work was to develop PC-based (micro)emulsionsand study the changes in their microstructures. Dispersion stabilityby droplet size and zeta potential determination were correlated withthe changes of interfacial tension. Pseudoternary phase diagrams havebeen constructed to evaluate the phase behavior of the systems containing n-tetradecane/phosphatidylcholine and water (or ethanol)at different weight ratios. The presence of ethanol changes the areaper lipid molecule and the layer thickness, therefore the capabilityof phospholipid adsorption at the oil/alcohol interface was dependenton the ethanol concentration and increases with its increase. Usingaqueous-ethanolic phase enables us to obtain a small region of o/wand w/o PC-based microemulsions. This study has shown that natureof biosurfactant, ethanol concentration, and proportion of the oilto water phase are the most important factors for processing and stabilityof the phosphatidylcholine-based emulsions. The obtained results expandthe characteristics of the oil/phospholipid systems, which may leadto large application potential. [ABSTRACT FROM AUTHOR]

Solvation thermodynamics-based models for predicting liquid-phase nonidealities and fluid-phase equilibria are gaining attention in modern chemical process and product development. Among this class of thermodynamic models, COSMO-RS and COSMO-SAC are two variants used extensively in industry. A key input to these models is the so-called sigma profile, i.e., a histogram of charge density distribution over the molecular surface. Typically, sigma profiles are generated from quantum mechanical calculations with molecular structure and conformation information as inputs to the calculation. We present an alternative approach for generating sigma profiles from experimental fluid-phase equilibrium data, i.e., solubility. Specifically, we incorporate the conceptual segment concept of NRTL-SAC activity coefficient model into sigma profile generation. We generate "apparent" sigma profiles from linear combination of sigma profiles of conceptual segments represented by reference molecules selected for hydrophobic, polar attractive, polar repulsive, and hydrophilic conceptual segments. Conceptual segment numbers of the molecule of interest are identified from regression of available experimental data. We show applicability of this sigma profile generation approach with solubility modeling for four drug molecules: caffeine, aspirin, paracetamol, and lovastatin. [ABSTRACT FROM AUTHOR]

Thiswork presents a modeling approach using the Perturbed Chain-StatisticalAssociating Fluid Theory (PC-SAFT) for new liquid–liquid equilibria(LLE) data of ternary systems containing β-myrcene, acetonitrile,and n-alkanes, as well as binary mixtures thereof.The modeling approach is based on parameter estimations from binarysystems and allows a general prediction of acetonitrile/n-alkane systems’ LLE and their ternary mixtures’ LLEwith β-myrcene. The binary mixtures’ vapor–liquidequilibria (VLE) of β-myrcene with acetonitrile and n-alkanes were measured at 100 mbar. The ternary systems’LLE were measured at ambient pressure and 298.15 K. Experimentallyinvestigated alkanes are n-hexane, n-heptane, and n-octane. The approach was validatedby successfully predicting the ternary system containing n-dodecane. [ABSTRACT FROM AUTHOR]

Activitycoefficients are used in phase equilibria calculationsto account for the nonideal behavior of liquids in a mixture. In ourprevious work, we proposed a modification to the widely used nonrandomtwo liquid (NRTL) activity coefficient model that reduced the numberof parameters from two to one. The current work is an extension tothe previous work, and it focuses on generalizing the parameter ofthe modified NRTL (mNRTL1) model using a theory-framed quantitativestructure–property relationship (QSPR) modeling approach, wherethe mNRTL1 model was used as a theoretical framework to develop thebehavior model, and QSPR was used to generalize the substance-specificparameter of the model. In this work, a VLE database consisting of916 binary systems with a wide range of functional-group interactionswas assembled. Data regression analyses were performed to determinethe parameter of the mNRTL1 model. The structural descriptors of themolecules were used as inputs in the QSPR model to predict the regressedparameter. The generalized QSPR model produced equilibrium propertypredictions within two times the errors obtained through regressionof the experimental data. The newly developed QSPR model resultedin comparable phase equilibria predictions to that of the group-contributionmethod, UNIFAC. In comparison, the QSPR model has less than 10% ofthe number of parameters used by UNIFAC and is applicable to a widerrange of systems. [ABSTRACT FROM AUTHOR]

An investigationof the phase equilibria of the glycine–methanol–NH4Cl–H2O system was carried out with the objectiveof optimizing the monochloroacetic acid (MCA) process for the productionof glycine. Phase equilibrium of the glycine–NH4Cl–H2O system at temperatures over the range of283.2–353.2 K was determined for concentrations ranging upto the multiple saturation points. The solubilities of both glycineand NH4Cl were found to increase with increasing temperature,as well as with increasing concentration of other solutes. The Bromley–Zemaitismodel for ions and the Pitzer formulation for glycine neutral speciesimplemented in the OLI platform were used in the regression of theexperimental solubilities. The average absolute deviations betweenthe regressed solubility values and the experimental data were foundto be 1.4% for glycine and 0.93% for NH4Cl. Three binaryinteraction parameters of the Pitzer formulation were newly obtainedand coupled with the Bromley–Zemaitis parameters documentedin OLI’s databank to predict the multiple saturation pointsof the system. Additionally, the solubility of glycine in methanol–H2O mixtures was also measured from 283.2 to 323.2 K, and asharp decline was observed as a function of the content of methanol.Such thermodynamic information is definitely useful for improvingthe existing industrial process, as well as providing fundamentalsfor the development of new glycine production processes. [ABSTRACT FROM AUTHOR]

Prediction of liquid–liquidphase equilibria in reactingsystems is important in many applications such as reactive extraction.This problem poses several numerical challenges. These systems aregoverned by highly nonlinear algebraic equations and are plagued bythe issue of nonconvergence of iterative algorithms. They exhibitstrong sensitivity to the choice of the initial values or startingguesses for the variables. The nonconvergence stems primarily fromthe wide range of concentrations of various species at equilibrium.In this work, a new methodology for predicting thermodynamic equilibriaof multiphase reacting systems is proposed. The mathematical formulationand solution are based on the use of the logarithms of the concentrationsas the dependent variables. The proposed algorithm shows rapid convergenceeven when the initial guesses are far from equilibrium. The efficiencyof the method is demonstrated by predicting the equilibrium concentrationsof species in three systems of varying degrees of complexity. [ABSTRACT FROM AUTHOR]

Presently, gas hydrates are beingstudied for their potential applicationsin technologies involving natural gas transportation, carbon dioxidesequestration, and component separation. In order to optimize theiruse, research has focused on finding hydrate-promoting agents andunderstanding how they work. One such promoter, multiwall carbon nanotubes(MWNTs), was found to enhance hydrate growth. The current study investigatesthe effects of adding plasma-functionalized hydrophilic MWNTs andas-produced hydrophobic MWNTs on the dissolution stage of methanehydrate formation. It was found that the addition of the hydrophilicMWNTs increased methane dissolution rates with an increase in MWNTloading. Furthermore, the hydrophobic MWNTs initially enhanced dissolutionup until a concentration of 5 ppm, at which point the rates beganto return to their nominal values. It was also found that the additionof either type of MWNT did not significantly affect the total numberof moles of methane dissolved in the water. [ABSTRACT FROM AUTHOR]

Gasinjection is a widely used enhanced oil recovery method, andits application is expected to increase in the foreseeable future.In order to build a method of characteristics solution to a two-phasegas injection system, we must construct the composition route fromthe injection gas to the initial oil where all the intersecting keytielines must be identified. Calculation of these intersecting tielinesrequires a series of special negative flashes, which allow not onlyphase fractions outside the physical interval [0,1] but also negativefeed compositions. The phase compositions from one negative flashare used to recombine the feed for the next negative flash. Despitethe apparent complexity due to multicomponent phase equilibrium andtransport, for pure component gas injection, negative flash and eliminationof components can be performed in an alternating manner. In particular,if K-values are constant, there exists a simple featurethat the vapor fraction roots (β-roots) for the Rachford–Riceequation for the initial oil are the roots to be found in all thenegative flashes involved. This leads to a simple and well-structuredalgorithm for the solution with constant K-values.A special problem with pure component gas injection is that therecould be two possible roots in the β-interval of interest. Butif the component to be eliminated is left with an infinitesimal amountdue to the diffusion or dispersion effects, only the larger root canstill give non-negative phase compositions and should thus be selected.For multicomponent gas injection with constant K-values,the vapor fraction roots in all the involved negative flashes aresimply from the vapor fraction roots for the initial oil (β-roots)and those for the injection gas (λ-roots). By solving just twonegative flashes for the initial oil and the injection gas and usingproper selection sequences for these β- and λ-roots, wecan readily determine all the intersecting tielines for constant K-values. [ABSTRACT FROM AUTHOR]

Thenonrandom two-liquid (NRTL) model is an activity coefficientmodel used widely in phase equilibria calculations. The NRTL modelhas three adjustable parameters that are determined through regressionof experimental data for a specific system. A generalization for themodel parameters would reduce the time, money and effort expendedon the collection of experimental data. This work focuses on the applicationof a theory-framed quantitative structure–property relationship(QSPR) modeling approach for the estimation of NRTL parameters. Adatabase of 342 low-temperature binary (10–40 °C) liquid–liquidequilibria (LLE) systems was employed in this work. Data regressionanalyses were performed to determine the NRTL model parameters. Structuraldescriptors of the molecules were generated and used in developinga QSPR model to estimate the regressed NRTL parameters. The newlydeveloped QSPR model uses 30 significant descriptors as inputs. Themodel yielded binary predictions with 8, 38, 51 and 44% absolute averagedeviation for the mole fractions (x1in1-rich phase and x1in 2-rich phase) andpartition coefficients (K1and K2), respectively. These errors are approximately3 to 4 times the errors found from the regression analyses. Further,we observed an 11% prediction failure rate, in which cases the modelfails to converge to an equilibrium solution. The application of thepopular and often employed UNIFAC-1981-LLE model resulted in 3 to7 times the errors obtained through regression analyses and a predictionfailure rate of 36%. These results demonstrate the efficacy of ourQSPR model in providing improved predictions and an increased rangeof applicability when compared to the UNIFAC-1981-LLE model for LLEsystems. [ABSTRACT FROM AUTHOR]

The Cubic-Plus-Association (CPA)equation of state (EoS) has alreadybeen proven to be a successful model for phase equilibrium calculationsfor systems containing glycols. In the present work, we interfacea thermodynamic property package (ThermoSystem), based on CPA, withAspen HYSYS through the CAPE-OPEN standards. We, then, simulate certainbinary and multicomponent systems where experimental data are availablein the literature and which are critical for process design of naturalgas dehydration units by triethylene glycol (TEG). We also demonstratethe potential of CPA for the process design of liquid–liquidextraction of aromatic hydrocarbons by TEG. Comparisons between simulationand experimental results are presented in order to illustrate thereliability of ThermoSystem while it is used in a process simulatorfor industrial applications. Detailed analysis on selecting TEG purecompound parameters and on calculating TEG–water binary parametersis shown. Missing binary interaction parameters are regressed andpresented for various binary systems, and a relationship between theinteraction parameters and alkane molecular weight is obtained forTEG–alkane binary systems. A simulation case study of a typicalnatural gas dehydration process is also presented. [ABSTRACT FROM AUTHOR]

Fastcooling to deep supersaturation for solvent crystallizationseems to have two major components. One involves mainly the thermodynamicsor phase equilibrium chemical thermodynamics of deep supersaturation.The other component focuses on the fast-cooling or heat-transfer aspect.All previous related crystallization work known to us involves a coolingprocess coupled with crystallization. This method does the coolingquickly to supersaturated conditions, so the cooling does not coupleor interfere with the subsequent isothermal crystallization at supersaturation.Although adiabatic cooling and isothermal crystallization are well-knownindividually, their combination here with proper choice of liquidand cooling ballast temperatures can achieve supercritical conditionsuniquely. [ABSTRACT FROM AUTHOR]

This study introduces a strategyto improve the effectiveness ofCuckoo Search (CS) algorithm for the unconstrained Gibbs free energyminimization in phase equilibrium calculations of nonreactive systems.Specifically, the gradient information of the unconstrained Gibbsfree energy function, which is readily available, is used to enhancethe balance between diversification and intensification stages ofthe CS algorithm for phase-split calculations in multicomponent systems.The results showed that it is feasible to improve the numerical performanceof the CS algorithm using the gradient information of the Gibbs freeenergy function; this improved method provides better results forphase equilibrium calculations in nonreactive systems with insignificantadditional computational effort. This gradient-based Cuckoo Search(GBCS) algorithm outperformed the conventional CS algorithm, in termsof its reliability and efficiency in solving phase equilibrium problems,especially for multicomponent systems. [ABSTRACT FROM AUTHOR]

Thedesign of a biphasic system is important for the developmentof liquid–liquid extraction and biphasic catalysis. In thiswork, we report a series of ternary biphasic systems that consistof hydrophilic ionic liquid (IL), water, and ethyl acetate. The effectsof the structure of the ILs (cation, anion, and substituent group),IL/water ratio, and temperature on the phase equilibrium of thesebiphasic systems were investigated. The mutual solubility was lowerin the IL/water–ethyl acetate biphasic system than in the water–ethylacetate system when ILs with strong hydration ability were introduced,such as [EMIm]OAc, [EMIm]Cl, [EMIm]NO3, [EMIm]EtSO4, and [HOEMIm]Cl. In addition, the hydrogen-bonding basicityof the IL-containing phase could be tuned by changing the IL structureor IL/water ratio. These novel IL/water-ethyl acetate biphasic systemsmay present another option in addition to hydrophobic IL–waterand aqueous biphasic systems for liquid–liquid extraction. [ABSTRACT FROM AUTHOR]

This paper reports the experimentallymeasured phase equilibriumconditions for the clathrate hydrates formed from simulated mine ventilationair (0.50 vol % CH4+ 99.50 vol % air) in the presenceof 0, 5, 20, 37.1, and 50 wt % of tetrabutylphosphonium bromide (TBPB).These equilibrium conditions were measured at the temperature rangeof 281.62–292.49 K and pressure range of 1.92–18.55MPa by using an isochoric equilibrium step-heating pressure searchmethod. The results showed that addition of TBPB allowed the hydratedissociation condition for mine ventilation air to become milder,and at a given temperature, the lowest hydrate dissociation pressurewas achieved at 37.1 wt % TBPB, corresponding to the stoichiometriccomposition for TBPB·32H2O. For each TBPB concentrationtested, the semilogarithmic plots of hydrate dissociation pressureversus reciprocal absolute temperature can be satisfactorily fittedto two straight lines intersecting at 6.5 MPa. The slopes of thesefitted straight lines are indifferent to changes in TBPB concentration.Gas composition analysis by gas chromatography also found that inthe presence of 37.1 wt % TBPB, CH4could be enriched approximately3.5-fold in the hydrate phase. [ABSTRACT FROM AUTHOR]

Thispaper reports on the ability of sPC-SAFT extended with thepolar terms of Gross and Vrabec (GV) and Jog and Chapman (JC) to predictthe phase equilibria of alkane/alcohol, alcohol/alcohol, and water/alcoholbinary systems. These non-hydrogen-bonding/hydrogen-bonding and hydrogen-bonding/hydrogen-bondingsystems are investigated using the 2B, 3B, and the newly developed2C association schemes for alcohols and the 4C scheme for water. Forthese selected binary systems, the GV and JC polar terms deliver similarresults when incorporated into sPC-SAFT. Notably, the 2C associationscheme offers improved predictions compared to the 2B and 3B associationschemes, especially when water/alcohol systems are modeled. [ABSTRACT FROM AUTHOR]

Liquid–liquid equilibriumdata of the system composed bysoybean oil, fatty acid methyl esters (FAMEs), methanol, and glycerolwere experimentally determined at temperatures of 25, 45, and 65 °C.Three binary systems (oil + methanol, oil + glycerol, and FAMEs +glycerol) and all the ternary combinations were evaluated. With thesedata, universal quasichemical (UNIQUAC) and non-random two-liquid(NRTL) binary interaction coefficients were calculated and validated.According to the results, the UNIQUAC model fitted the experimentaldata better than the NRTL one. In order to complete this study, UNIQUACbinary interaction coefficients for the mixtures of oil, FAMEs, methanol,and glycerol with monoglycerides and diglycerides were also predictedusing a group contribution model (universal quasichemical functional-groupactivity coefficients) and checked using experimental data from thesoybean oil transesterification reaction. [ABSTRACT FROM AUTHOR]

Thisarticle deals with the phase stability analysis of multicomponentsystems via the determination of all the stationary points of theso-called tangent plane distance function, which is known as an importantbut difficult problem of the thermodynamics of phase equilibrium,where high nonlinearities are inherent aspects of the different thermodynamicmodels commonly used in the description of this distance function.To analyze phase stability described from different models, we combinethree basic procedures here that were selected in order to attackpoints that we deem of relevant difficulty. To this end, we encapsulatein a single iterative algorithm the following steps: (i) polarizationof a merit function associated with first-order stationary conditionsof the phase stability problem, in order to avoid (or at least minimize)the repetition of stationary points previously calculated; (ii) astochastic optimization method, which (at each iteration of the encapsulationalgorithm) minimizes mtimes the same merit functionpolarized with the predetermined stationary points, using mdifferent seeds for a reliable random number generator(where mis a given integer), in order to calculatenew stationary points; (iii) a change of variables designed to allowthe numerical method to work in the unconstrained optimization framework,providing the location of stationary points near the boundary of theoriginal feasible set. Using the NRTL and UNIQUAC models for liquid–liquidequilibria at low pressures and the Soave–Redlich–Kwongand Peng–Robinson cubic equations of state for vapor–liquidequilibria at high pressures, we analyze 9 multicomponent systemsstudied in the literature, equipped with different feed compositions,totaling 32 tested mixtures, whose component numbers ranged between3 and 12. We show 14 new stationary points obtained here that werenot detected by methods previously used by other authors. [ABSTRACT FROM AUTHOR]