Phase Behavior Of Multicomponent Systems Research Articles

Multi–component Cahn–Hilliard Systems with Singular Potentials: Theoretical Results

We consider a system of nonlinear diffusion equations modelling (isothermal) phase segregation of an ideal mixture of Nge 2 components occupying a bounded region Omega subset mathbb {R}^{d},dle 3. Our system is subject to a constant mobility matrix of coefficients, a free energy functional given in terms of singular entropy generated potentials and localized capillarity effects. We prove well-posedness and regularity results which generalize the ones obtained by Elliott and Luckhaus (IMA Preprint Ser 887, 1991). In particular, if dle 2, we derive the uniform strict separation of solutions from the singular points of the (entropy) nonlinearity. Then, even if d=3, we prove the existence of a global (regular) attractor as well as we establish the convergence of solutions to single equilibria. If d=3, this convergence requires the validity of the asymptotic strict separation property. This work constitutes the first part of an extended three-part study involving the phase behavior of multi-component systems, with a second part addressing the presence of nonlocal capillarity effects, and a final part concerning the numerical study of such systems along with some relevant application.

P-T-x Measurement and Modeling of Methane + Propane + Methanol or 2,2′-[Ethane-1,2-diylbis(oxy)] Di(ethan-1-ol) and Methane + Propane + Methanol + 2,2′-[Ethane-1,2-diylbis(oxy)] Di(ethan-1-ol) Systems

Limited phase equilibria data exist for multicomponent systems encountered in the natural gas processing industry. To address this gap, bubble point measurements were performed for methane + propane + methanol; methane + propane + (2,2′-[ethane-1,2-diylbis(oxy)] di(ethan-1-ol) or triethylene glycol); methane + propane + methanol + triethylene glycol systems in the temperature range of 283.16 to 323.16 K and a pressure range of 0.78 to 13.79 MPa. A visual synthetic high-pressure cell comprising a sapphire tube of 33 cm3 working volume was used. The new experimental P-T-x data were modeled using the Cubic Plus Association (CPA) model and the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) model. Model correlations with the CPA model yielded better results than those with the PC-SAFT model, with a maximum absolute average relative deviation in pressure of 6.97% and 7.33%, respectively. The CPA model predictions based on binary parameters alone do not adequately describe phase behavior of multicomponent systems.

Phase behavior of multi-component hydrocarbon systems in nano-pores using gauge-GCMC molecular simulation

In recent years, the phase behavior of hydrocarbons in shale reservoirs has received significant attention. One of the main complexities in modeling the phase behavior in shale reservoirs is the confinement effect. Surface–fluid interactions in nanoscale shale pores can lead to a heterogeneous distribution of molecules and can significantly alter the phase behavior compared to that in bulk conditions. Molecular simulation has shown promising results in modeling phase behavior under confinement. In this study, we present a novel molecular simulation method for studying the confinement effect on the phase behavior of multicomponent systems. We validate our method by comparing the phase diagrams of pure and binary hydrocarbon systems with experimental data (where available) and the simulation results from other techniques. We also apply the proposed method in modeling the phase behavior of a ternary system (C1/C3C5) under a 4 nm slit pore confinement. Our results show that critical density increases under confinement in binary and ternary systems, and the confinement effect produces in a significant shift in the composition of the critical point. Heavier components have a higher concentration in the adsorbed layers than that of lighter components, which results in significant phase density differences under confinement.

Hydrogen solubility in heavy oil systems: Experiments and modeling

Hydrogen solubility measurements in heavy oils are required in order to develop accurate process models. Nevertheless, these solubility measurements are challenging at elevated temperatures and pressures and the amount of data points is scarce in the literature. This paper presents measured hydrogen solubilities in heavy oil systems at a temperature range from 498 to 598K and a pressure range from 2 to 11MPa. The experiments were conducted with a continuous flow apparatus. One of the well-characterized heavy oil systems was a hydrocracked vacuum gas oil and the second system consisted of a modified vacuum residue from Urals crude and toluene. The modified vacuum residue and toluene mixtures were prepared gravimetrically (mass fractions of vacuum residue: 0.25, 0.34 and 0.50). The experiments demonstrated that increasing the partial pressure of hydrogen and temperature increased the hydrogen solubility. Another finding was that the amount of toluene in the system had great impact to the hydrogen solubility. Four modeling approaches were compared based on their predictions on the hydrogen solubility in heavy oil systems measured in this work and four heavy oils found from the literature. The chosen models were PC-SAFT, Peng–Robinson, a simple correlation based on the corresponding theory and a method based on the Scatchard–Hildebrand theory. PC-SAFT with applied a heavy oil characterization method and the correlation based on the corresponding theory were found to predict the hydrogen solubility equally well and accurately. The benefit of using PC-SAFT instead of the simple correlation is that with PC-SAFT, phase behavior of multicomponent systems can be predicted and other properties, such as densities, can be obtained simultaneously. Peng–Robinson with a single carbon number characterization method overestimated the hydrogen solubility in the studied heavy oils and the method based on the Scatchard–Hildebrand theory could model the hydrogen solubility well after parameter regression.

Synchrotron X-ray Scattering techniques for soft matter industrial research and development

Consumer products based on soft matter technology often exhibit macroscopic properties which are strongly dependent on their micro- and nano-structures extending over multiple size scales. Synchrotron scattering techniques are ideally suited for probing these multilevel structures and deliver complementary and in some cases unique information as compared to real space methods like confocal microscopy, cryo-electron microscopy or atomic force microscopy. The European Synchrotron Radiation Facility (ESRF) is a world-leading synchrotron light source which operates several state-of-the-art instruments for the investigation of soft materials and offers expertise to academic and industrial users. Fast and flexible access for proprietary experiments with a modular, fine-tuned service is guaranteed. A range of dedicated sample environments which mimic industrial processing conditions are available. This presentation will illustrate the state-of-the-art performance of the following synchrotron scattering techniques by recent examples of industrial relevance. Simultaneous small and wide angle X-ray scattering (SAXS/WAXS) is a powerful method to determine the microstructure and phase behavior of multi-component systems like detergents, food products, pharmaceutical components, polymer composites, etc. The high photon flux translates to high throughput measurements, while the high degree of collimation and resolution permit to elucidate a wide range of length scales from a few Angstroms up to micron scale. Scanning microbeam SAXS/WAXS and single micro-crystal/fiber diffraction (µXRD) allows elucidating the local nanostructure of very small objects like micro-specimens of composite organic/inorganic materials, teeth, bones, micromechanical parts, polymer fibers, micro fluidics, etc. with micro/nanometric real space resolution. X-ray reflectivity (XR) and grazing incidence diffraction/scattering (GID /GISAXS) can reveal the nanoscale structure and complexity of nano-structured complex fluids at interfaces, organic films, biological membranes, etc.

Role of pseudopolymorphism on concentration dependent competitive adsorption at a liquid/solid interface

We present for the first time a peculiar concentration effect on competitive adsorption of a binary mixture at the liquid/solid interface, which we attribute to the existence of pseudopolymorphism and its concentration dependence. These results are helpful for the understanding of phase behavior of multi-component systems at the interface.

Representation of high‐dimensional, molecular solid‐liquid phase diagrams

AbstractA generic framework for the representation of multicomponent molecular solid‐liquid phase diagrams in the form of digraphs is presented. Pure components, eutectic points, and saturation points in the solid‐liquid composition space are represented as vertices of the digraph. These vertices are connected to form edges on the basis of the adjacency matrix, which is constructed by following a set of generic rules derived from the Gibbs phase rule. These edges form the boundaries of high‐dimensional saturation varieties. Included in the framework is a procedure for plotting high‐dimensional isobaric and isothermal isobaric phase behavior in the form of projections and cuts. With this framework, solid‐liquid phase behavior of multicomponent systems can be easily represented and studied. Applications include facilitation of experimental development of high‐dimensional phase diagrams and synthesis of crystallization‐based separation processes. The latter is illustrated with the separation of a quinary mixture.

The Group Contribution Concept: A Useful Tool To Correlate Binary Systems and To Predict the Phase Behavior of Multicomponent Systems Involving Supercritical CO2 and Fatty Acids

In this paper, a purely predictive model for the phase equilibria computation of mixtures involving fatty acids (FA) and supercritical carbon dioxide (SC-CO2) is proposed. In a first step, the phase equilibria modeling of FA/CO2 binary systems were performed using the Peng−Robinson equation of state. To obtain a purely predictive model, the group contribution method developed by Abdoul et al. which allows the prediction of the binary interaction parameters (kij) was extended to FA compounds. In a second step, the proposed model was used to predict the phase equilibria data of ternary and quaternary systems found in the literature. In a last step, bubble-point and dew-point pressures of systems involving CO2 and multicomponent mixtures of FA were measured in our laboratory, and the previous model was used in order to check its capability in predicting these data.

Phase behavior of multicomponent systems water-oil-amphiphile-electrolyte. 3

Dans le cas du systeme du titre, comparaison de l'influence des sels hydrotropes, en particulier de NaClO 4 et de (C 6 H 5 ) 4 PCl, qui ne sont pas tensioactifs, avec celle du laurylsulfate de sodium, detergent ionique. On montre que les influences de ces 2 types de sels sont presque similaires, ce qui est important pour l'etude de la microstructure des microemulsions

The Use of Pseudocomponents in the Representation of Phase Behavior of Surfactant Systems

Abstract A new method is developed to represent the phase behavior of multicomponent systems. This method uses fewer pseudocomponents than true components, but unlike conventional methods in which pseudocomponents are often chosen arbitrarily, the pseudocomponents are often chosen arbitrarily, the method uses regression analysis to find a "best" set of pseudocomponents.The method is applied to two surfactant systems of the type used for tertiary oil recovery. One system contains a crude oil (from the North Burbank Unit, Osage County, OK) and the other contains a pure hydrocarbon, 1-phenyltetradecane. For both systems the representation in terms of the pseudocomponents chosen by the regression analysis is significantly more faithful than that obtained by conventional methods.Since the considerations discussed here are general, they should be applicable to a wide range of phase studies in multicomponent systems. For example, they should be illuminating when applied to oil recovery by gas injection (carbon dioxide, natural gas, etc.), and to extraction processes, as well as to surfactant systems. Introduction Systems containing surface active agents have attracted a great deal of attention in connection with tertiary oil recovery. In many of these systems optimum oil recovery has been found to be strongly correlated with the phase behavior of these systems. To understand completely the basis for these correlations, one must be able to represent the phase behavior of systems containing surfactants adequately.Surfactant systems for tertiary oil recovery usually contain at least five components: oil, water, surfactant. cosurfactant, and electrolyte. The isothermal, isobaric phase diagram of these systems can be represented in a phase diagram of these systems can be represented in a four-dimensional space. Because physical representation (in three dimensions) of such a diagram is impossible. various techniques have been developed to attempt to represent the phase behavior in lower dimensional spaces. All these techniques correspond to projections of the original diagram onto lower dimensional spaces. Although almost unlimited methods of projection exist, only a small fraction convey useful information.Two projection schemes having some similarities but different intents and consequences are straight mathematical projection and "pseudocomponent" projection. Straight mathematical projection refers to the process of directly projecting the four-dimensional data for the entire phase diagram along some specified direction onto a three-dimensional space. All information parallel to the direction of the projection is lost. For example, if the rays of projections are parallel to the oil/water edge of the phase diagram, the resulting representation contains no information about the relative amounts of oil and water in the phases. In principle, this problem can be circumvented by generating two representations corresponding to projections of the same data along two different directions. For example. a second representation could be produced corresponding to a projection parallel to the water/alcohol edge of the phase diagram. parallel to the water/alcohol edge of the phase diagram. Although neither representation contains complete information, the pair of representations does contain all information about the system. The problem with this method is that the information is not perceived easily and, since the intent of using phase diagrams is usually to make visible a summary of the phase trends, such mathematical representations are not very useful.The second and generally more useful projection scheme uses pseudocomponents. A pseudocomponent is some mixture of pure components treated as a single component. SPEJ P. 289