Study Of Phase Behavior Research Articles

Microvolume Screening of Extraction and Phase Behavior in a Liquid-Liquid Microsystem.

Spontaneous formation of a third immiscible phase during liquid-liquid solvent extraction presents an enormous technical challenge for industry. Insight from current empirical investigations is greatly limited by the lack of methodologies that simultaneously report the progress of the extraction, third-phase onset time, and chemical and physical nature. The microfluidic strategy presented here answers this challenge by supporting an optically transparent submicroliter organic-phase film in a micropillar array surrounded by the aqueous phase. To demonstrate, we used 1 M Cyanex 572 in Shellsol D70 (organic phase) to extract Yb3+ and Dy3+ from a pH 2 aqueous phase. Real-time optical tracking confirmed that the visual onset of third-phase formation is consistent with the cessation of extraction (at the loading limit). Spectroscopic analysis of the solid-like third phase was carried out successfully. The new analytical approach offers a step change in speed and efficiency for reagent development, process control, and fundamental studies of complex phase behavior in reactive multiphase systems.

On the Universality of Capillary Condensation and Adsorption Hysteresis Phenomena in Ordered and Crystalline Mesoporous Materials

AbstractUsing adsorption experiments for argon over a wide range of temperatures from above the triple point (i.e., 87 K) down to 65 K, coupled with advanced molecular simulation studies, the underlying mechanism of capillary condensation and hysteresis in a mesoporous metal‐organic framework (MOF), MIL‐101(Cr) is explored. The results obtained on the mesoporous MOFs are compared with the experimental and molecular simulation studies of argon adsorption and phase behavior in mesoporous molecular sieves (e.g., MCM‐41 silica) of similar pore size and over the same temperature range (65–87 K). The studies provide insights into the nature of confinement effects on the adsorption and phase behavior of fluids in mesoporous MOFs. The obtained results suggest that certain features of adsorption, capillary condensation, and associated hysteresis phenomena in mesoporous MOFs and in mesoporous molecular sieves are governed by the same underlying physics, despite the striking differences in pore structure and chemical composition. Hence, the findings are of importance for advancing characterization methodologies based on gas adsorption, but also for predicting the behavior of mesoporous MOFs in various potential applications.

Nanoemulgel for Improved Topical Delivery of Retinyl Palmitate: Formulation Design and Stability Evaluation.

Retinyl palmitate is a vitamin A ester belonging to the family of endogenous natural retinoid and used to treat various skin disorders like acne, skin aging, wrinkles, and dark spots, as well as to protect against psoriasis. Despite the known therapeutic benefits of retinyl palmitate, the conventional topical delivery of retinyl palmitate commonly associated with adverse reactions such as skin irritation, redness, excessive peeling, and dryness. Therefore, the current study aims to encapsulate the retinyl palmitate in nanoemulsion then incorporate it into a hydrogel system to improve the topical delivery and stability. Low-energy emulsification method was used for the nano-encapsulation of retinyl palmitate. The phase behavior study was used for the investigation and the optimization of the formulation. The droplet size of the optimized nanoemulsion was in nano dimension (16.71 nm) with low polydispersity index (PdI) (0.015), negative zeta potential (−20.6 mV). It demonstrated the influence of vortexing on droplet size and PdI during nanoemulsion preparation. The retinyl palmitate loaded nanoemulgel delivery system exhibited significant improvement (p < 0.05) in skin permeability after topical application. Employment of the nano-encapsulation approach afterward dispersion into hydrogel system for the development of a topical delivery system of retinyl palmitate resulted in improvement in its UV and storage stability as well.

A fluid dynamic study of the active phase behavior in a rotary drum with flights of two and three segments

In the rotary dryers with flights, the drying occurs mainly in the active region where the material comes into direct contact with the air stream. The design of these flights is a complex task and studies are necessary to gain an in-depth understanding of the particle dynamics. This work aims to investigate the effects caused by angulations in flights of two and three segments on the particle dynamics, especially in the active region. The prediction of the solids flow was investigated by simulation using a Discrete Element Method (DEM) approach in an open-source software LIGGGHTS®. The simulated results were compared with experimental data using glass beads, with the rotary drum operating with 12 flights. The active region characteristics were analyzed using the responses variables: mass of solids in active phase, percentage of active region area occupied by the particles and the dispersion of the particles in the active region.

A novel visualization approach for foamy oil non-equilibrium phase behavior study of solvent/live heavy oil systems

In this study, a novel visualization methodology to study solvent non-equilibrium exsolution behavior in heavy oil systems is proposed. A Hele-Shaw-like visual cell with adjustable aperture depth, has been designed to overcome the shortcomings of traditional apparatuses such as a hardly-visual PVT cell, or non-visual transfer cylinders. By eliminating the 3D nature of the traditional apparatuses, the true 2D bulk phase visual cell can directly visualize the interface evolution of foamy oil under pressure depletion. Totally, 6 sets of Constant Composition Expansion tests (CCE) were conducted with a CO2-C3H8-heavy live oil system. The effect of pressure depletion rates on solvent non-equilibrium exsolution behavior have been tested. Meanwhile, the initial volume fill-up percentage of live oil in the visual cell was also found to have an effect on foamy oil generation and endurability. This helps to define the appropriate volume of live oil to be saturated in PVT tests that aim to induce non-equilibrium. Through analyzing the deviation of liquid/vapor phase volume fraction from equilibrium state, non-equilibrium regimes of solvent exsolution were effectively found. The experimental design is also able to continuously capture the real-time solvent component exsolution sequence during pressure depletion. Numerical simulation of solvent non-equilibrium exsolution behavior has been conducted by a MATLAB-controlled reservoir simulator with real-time optimization. By dynamically adjusting the K value in the simulator, the total flashed vapor phase volume and the individual solvent component mass was history-matched. The achieved non-equilibrium K values were compared with equilibrium K values, and a delayed solvent exsolution was indicated.

Heat Capacities of l-Alanine, l-Valine, l-Isoleucine, and l-Leucine: Experimental and Computational Study

This work is part of the effort on establishing reliable thermodynamic data for amino acids and, in a broader context, benchmarking first-principles calculations of thermodynamic properties of molecular crystals against reliable experimental data. In this work, crystal heat capacities of l-alanine (CAS RN: 56-41-7), l-valine (CAS RN: 72-18-4), l-isoleucine (CAS RN: 73-32-5), and l-leucine (CAS RN: 61-90-5) were newly measured in the temperature range 262–450 K by Tian–Calvet calorimetry and power-compensation differential scanning calorimetry (DSC) and combined with the critically assessed literature data to obtain the reference data from near 0 to 450 K. The heat capacity measurements were accompanied by thermogravimetric analysis to determine the decomposition temperatures of the studied amino acids and phase behavior studies by X-ray powder diffraction and heat-flux DSC to identify the initial crystal structures and their possible transformations. The crystal heat capacities calculated by combining the...

Influence of inter- and intramolecular H-bonding on the mesomorphic and photoswitching behaviour of (E)-4-((4-(hexyloxy)phenyl)diazenyl)-N-phenyl benzamides.

We report on the synthesis, phase behaviour and photoswitching studies of new azo linked rod-shaped molecules. These novel materials consist of three phenyl rings separated by a diazo, amide linkage with a hexyloxy tail and 2,4-substituents at either end of the phenyl ring. The mesomorphic behaviours, phase transition temperature including the enthalpies were characterized by polarizing optical microscope (POM) and differential scanning calorimetry (DSC). The influence of inter- and intramolecular hydrogen bonding on mesomorphic and photoisomerization was studied. Photoisomerization studies carried out both in the solid and liquid phase show the quick E–Z transition with prolonged thermal back relaxation (Z–E) by using UV-Visible spectroscopy. This interesting behaviour could be attributed to the presence of the hexyloxy tail, lateral electron withdrawing group and the influence of inter- or intramolecular hydrogen bonding. Excellent bright and dark states were accomplished using one of these materials in optical storage device. Further tuning is necessary to employ them for real applications.

2-D physical model experimental study of ethyl acetate and steam co-injection for in-situ bitumen recovery

In this work, we evaluate ethyl acetate (EA) as a solvent for bitumen recovery using a 2-D sand-pack physical model for the first time. EA was considered for co-injection with steam due to the promising results obtained from our recent experimental phase behavior and reservoir simulation studies. Two experiments were conducted by co-injection of 10 and 20 vol% of EA with steam to evaluate expanding solvent steam assisted gravity drainage (ES-SAGD). An experiment was also conducted for the steam assisted gravity drainage (SAGD) as a reference case. The results showed that co-injection of EA increases the bitumen rate. Both ES-SAGD experiments showed a higher production rate compared to SAGD and the superiority of ES-SAGD. The results of 10 and 20 vol% EA co-injection revealed ~65% and ~75% bitumen recovery, respectively, compared to 50% in the case of the SAGD experiment. Co-injection of EA with steam also decreased the cumulative steam-oil-ratio (cSOR), which is desirable in bitumen recovery processes. ES-SAGD experiments reduced the cSOR by 1.5 to 2.5 units, which is 20 to 32% lower than SAGD. This reduction in cSOR results in significant energy savings and lower greenhouse gas emission intensity. The cumulative energy-oil-ratio was also measured, and the results showed that co-injection of EA decreases the energy-oil-ratio by 17–22% compared to SAGD. Moreover, it was observed that implementation of EA significantly reduces the water-oil emulsion stability, which is favorable in oil/water separation and treatments of the produced water.

Molecular interactions between gelatin and mucin: Phase behaviour, thermodynamics and rheological studies

This work studies the interactions, thermodynamics, phase behaviour, and rheology of mucin/gelatin binary mixtures. Addition of gelatin in mucin solutions at pH 7 leads to aggregation and phase separation, while such phenomena are not observed at lower pH values. Zeta potential measurements show that electrostatic interactions lead to the formation of soluble complexes between the mucin and gelatin at pH 3. However, steric exclusions are the prime candidates for inducing any interactions between the two macromolecular populations at pH 7. Fluorimetry shows two binding regimes for mucin/gelatin mixtures at pH 3, and one at pH 7. ΔG show higher negative value at pH 7, as compared to pH 3; this can account for the tendency of gelatin to flocculate in the presence of mucin at neutral environments but not in acidic ones. The Trouton ratio (ratio of extensional to shear viscosity) is low at pH 3, but unusually high at pH 7 due to the aggregated structures. The above highlight the molecular events leading to the flow of gelatin-based foods during oral processing.

Enhanced cryogenic packed bed with optimal CO2 removal from natural gas; a joint computational and experimental approach

Cryogenic separation technologies for CO2 capture have been proven promising due to a less negative environmental impact, and their capabilities to handle high CO2 content natural gas. Design and operation of a cryogenic CO2 capture process require appropriate phase behaviour study of the natural gas components and optimization due to high cooling duty. In this work, Aspen HYSYS simulator along with Peng Robinson property package was used for the thermodynamic phase study of the natural gas. A dedicated experimental setup comprises of a cryogenic packed bed along with an efficient control system was designed and fabricated for the separation study. High CO2 content natural gas with 75 and 90 mol% CO2 was used as a feed gas. The research work shows three optimum conditions for the mixture having 75% CO2, i.e. at 4, 10 and 14 bar pressure and at −139.8, −132.6 and −121.3 °C temperature, respectively. For the feed with 90% CO2, the obtained optimized pressure and temperature were 5, 8, and 9 bar, at −121.4, −110.5 and −105.8 °C, respectively. Both of the predicted showed an excellent agreement with the experimental thermodynamic data. This research work is promising to overcome the energy crisis by utilizing the contaminated natural gas reservoirs and can reduce carbon footprint by capturing CO2 at the source.

The role of biodegradable surfactant in microbial enhanced oil recovery

Many aerobic microorganisms can produce bio-surfactants which are capable of effectively reducing interfacial tensions between oil, water and rock. However, there are few publications on the production of bio-surfactants from anaerobic organisms. The combined effect of bio-surfactant, green surfactant and alcohol in the MEOR process, are not well understood yet and require further investigation. This experimental study was conducted to examine the effectiveness of combination of two microbial by-products, bio-surfactant and bio-alcohol, in recovering residual oil within the pores of rock. It also considered whether bio-surfactant capability could be improved by blending it with non-ionic green surfactant. Two formulations of surfactant and co-surfactant mixtures were selected for core-flood experiments based on phase behaviour study and IFT reduction to examine their potential for enhanced oil recovery. In the first formulation, JF-2 bio-surfactant was mixed with butanol; it was found that this formulation did not produce a significant quantity of incremental oil after water flooding. Lastly, a bio-surfactant (anionic) was blended with non-ionic green surfactant alkyl polyglucoside and butanol; this produced about 25% tertiary oil and 64% OIIP.

Ethyl acetate as a bio‐based solvent to reduce energy intensity and CO2 emissions of in situ bitumen recovery

AbstractWe introduce ethyl acetate (EA), a bio‐based chemical, as a potential solvent for bitumen recovery through comprehensive phase behavior and numerical simulation studies. Phase behavior and thermophysical properties of EA/live bitumen are measured at temperatures and pressures up to 190°C and 4 MPa, respectively. Experimental studies suggested that coinjection of EA with steam can reduce the bitumen viscosity by several orders of magnitude. Our numerical simulations show that coinjection of 2–8 mol% EA with steam can significantly reduce the steam‐oil‐ratio (SOR) by almost 0.9 units while increasing the bitumen production rate. This reduction in SOR can be translated to significant energy saving of ~2.2 GJ, emission reduction of ~120 kg of CO2, and wastewater reduction of ~120 m3 per ton of the produced bitumen, which are almost 20–25% lower than the steam‐assisted gravity drainage (SAGD) process.

Impact of Bioorganic Additives of Different Nature on Aggregation Behavior and on Cloud Point Temperatures of Nonionic Surfactants Tergitol NP-7 and Triton X-114 in Buffer Solutions

Aqueous biphasic systems containing non-ionic ethoxylated surfactants are perspective as media for some biochemical reactions. A comprehensive study of phase and aggregation behavior of these micellar systems, as well as consideration of the effects of biocomponents, their nature and concentration, pH and temperature are evident. In this work, the influence of salt medium (phosphate buffer), pH and temperature, as well as the presence of different bioorganic additives on cloud point and structural-thermodynamic properties (CMC and aggregation number) were studied for micellar solutions of non-ionic surfactants Triton X-114 and Tergitol NP-7 in water and buffers with pH 6.8, 4.3, 2.7. As additives were used the components of a biocatalytic hydrolysis reaction of penicillin G, namely penicillin G potassium salt, phenylacetic acid, and 6-aminopenicillanic acid. The different effects of the biocomponents on the cloud point and CMC value of Triton X-114 in the buffer with pH 4.3 are discussed. In addition, it was shown that the CMC value and the aggregation number of Triton X-114 decrease in buffer solutions (salting-out effect) and the CMC value increase at growing the temperature to 37°C (what is typical for ethoxylated non-ionic surfactants). The addition of phenylacetic acid (10 mM) leads to a reduction in the aggregation number of Triton X-114 at pH 4.3; other bio-additives have practically no effect. Thus, the studied additives have different effects on the structure and phase behavior of investigated micellar solutions, and this is an important aspect for choosing an extraction system to carry out a bioreaction.

Minireview - Microtubules and Tubulin Oligomers: Shape Transitions and Assembly by Intrinsically Disordered Protein Tau and Cationic Biomolecules.

In this minireview, which is part of a special issue in honor of Jacob N. Israelachvili's remarkable research career on intermolecular forces and interfacial science, we present studies of structures, phase behavior, and forces in reaction mixtures of microtubules (MTs) and tubulin oligomers with either intrinsically disordered protein (IDP) Tau, cationic vesicles, or the polyamine spermine (4+). Bare MTs consist of 13 protofilaments (PFs), on average, where each PF is made of a linear stack of αβ-tubulin dimers (i.e., tubulin oligomers). We begin with a series of experiments which demonstrate the flexibility of PFs toward shape changes in response to local environmental cues. First, studies show that MT-associated protein (MAP) Tau controls the diameter of microtubules upon binding to the outer surface, implying a shape change in the cross-sectional area of PFs forming the MT perimeter. The diameter of a MT may also be controlled by the charge density of a lipid bilayer membrane that coats the outer surface. We further describe an experimental study where it is unexpectedly found that the biologically relevant polyamine spermine (+4e) is able to depolymerize taxol-stabilized microtubules with efficiency that increases with decreasing temperature. This MT destabilization drives a dynamical structural transition where inside-out curving of PFs, during the depolymerization peeling process, is followed by reassembly of ring-like curved PF building blocks into an array of helical inverted tubulin tubules. We finally turn to a very recent study on pressure-distance measurements in bundles of MTs employing the small-angle X-ray scattering (SAXS)-osmotic pressure technique, which complements the surface-forces-apparatus technique developed by Jacob N. Israelachvili. These latter studies are among the very few which are beginning to shed light on the precise nature of the interactions between MTs mediated by MAP Tau in 37 °C reaction mixtures containing GTP and lacking taxol.

The use of solubility parameters and free energy theory for phase behaviour of polymer-modified bitumen: a review

Advances related to the use of solubility parameters and free energy theory for the phase behaviour study of polymer-modified bitumen (PMB) are reviewed in this paper. The origin and effects of PMB phase behaviour are criticised with a focus on PMB storage stability, morphology and swelling ratio. An overview of the solubility approach for studying PMB is given regarding the historical and future developments. Free energy expressions for PMB systems are analysed, including the free energy of mixing, elastic free energy and gradient energy. The kinetic aspects are discussed with respect to the diffusion and flow processes. It is indicated that the solubility bodies in the three-dimensional Hansen space and their degree of intersection can be useful for analysing the PMB thermodynamic equilibrium and thus storage stability. But they give no indication by themselves on the PMB morphology. With solubility parameters linked to the PMB free energy, however, an integrated thermodynamic approach can assist in understanding both PMB storage stability and morphology comprehensively. Due to the chemical complexity of bitumen and certain modifiers, the solubility body centres and radiuses should be both considered for a proper expression of the polymer-bitumen interaction in PMB. A hypothetical dilution process can simplify this process, but with limitations. The introduction of elastic free energy may lead to a new and more realistic expression of free energy for PMB system. With this overview, it is expected that a preliminary foundation is established towards a comprehensive and realistic thermodynamic framework for interpreting and predicting PMB phase behaviour.

A versatile simulation method for studying phase behavior and dynamics in colloidal rod and rod-polymer suspensions.

Here, we present an implicit-solvent model for dynamic simulations of hard-rod and rod-polymer suspensions. Individual rods are represented by a rigid linear chain consisting of overlapping spheres which interact through a pseudohard-core potential based on the cut-and-shifted Mie (generalized Lennard-Jones) potential with exponents (50, 49). In the rod-polymer suspensions, the polymers are modeled as freely interpenetrable spheres with respect to each other, while there is the pseudohard-core repulsion between the polymer and rod spheres. Dynamic simulations with this model are carried out with a dissipative particle dynamics (DPD) thermostat-each sphere is put in a larger DPD sphere and thus interacts with others via additional pairwise frictional and random forces-which captures the effects of Brownian forces due to the solvent while conserving local momentum. The phase behavior of these models, obtained from continuous compression and expansion simulations, reproduces previous predictions based on theoretical calculations and Monte Carlo simulations. Our method is suited to study dynamic processes in these suspensions, including nucleation and self-assembly, and can be readily extended to colloidal particles of different shapes and chemistry.

Kinetics of Inverse Melting/Crystallization of Poly(dialkoxyphosphazenes)

We have carried out a study of an unusual phase behavior of poly(dialkoxyphosphazenes) with pentoxy, butoxy, and propoxy substituents forming columnar mesophases which undergo a reversible transition into amorphous rubberlike state on cooling and reverse conversion into the original mesophases upon subsequent heating. On heating to around 200 °C they also yield isotropic melts. The DLI technique and polarized light microscopy were used for monitoring the overall rate of inverse 2D crystallization and linear growth rate of mesomorphic lamellae. The obtained kinetic data were treated in the framework of the Avrami approach and classical nucleation-controlled crystallization theory. Summarizing the results of our optical studies, we have concluded that the formation of 2D columnar mesophases in PDAP-C(3÷5) both in the usual way from the isotropic melt on cooling and via inverse freezing (crystallization) on heating the low-temperature reentrant amorphous phases is induced by heterogeneous athermal nuclei growing in two dimensions and yielding eventually a lamellar mesophase morphology.

From single gemini surfactants in water to catanionic mixtures with the bile salt sodium taurodeoxycholate: Extensive micellar solutions, coacervation and liquid crystal polymorphism as revealed by phase behavior studies

Gemini surfactants and bile acid salts are interesting amphiphiles owing to their unconventional and versatile molecular structure, and consequent unusual aggregation properties. In this work, we investigated the phase behavior of binary surfactant/water systems for the cationic bis-quat gemini surfactants 12-2-12 (short spacer) and 12-6-12 (intermediate spacer) and subsequently catanionic mixtures of each gemini surfactant and the bile salt sodium taurodeoxycholate, STDC. The phase diagrams and phase structure were unraveled by polarized light microscopy, differential scanning calorimetry, deuterium NMR and small angle X-ray scattering. The 12-2-12 and 12-6-12 gemini form a micellar-lamellar-cubic and micellar-hexagonal-cubic phase sequence, respectively, denoting the strong influence of the spacer length on the self-assembly properties. Both the catanionic 12-2-12/STDC/water and 12-6-12/STDC/water systems display a rich mesomorphic behavior. One of the most striking features is that the STDC micelles are able to incorporate enormous amounts of gemini surfactant, forming an extremely wide solution region of mixed micellar structures. By contrast, the gemini micelles can only solubilize limited amounts of STDC. The liquid crystalline phases from the binary systems incorporate sizeable amounts of the counterpart surfactant, forming mixed catanionic aggregates at high concentration. Interestingly, the dilute region of both systems is dominated by liquid-liquid phase separation implying the formation of aqueous two-phase micellar systems. The observed features are qualitatively rationalized in terms of packing and electrostatic effects between the surfactants at play.

Correlation of synthesis parameters to the phase segregation and lattice strain in tungsten oxide nanoparticles

Crystalline phase, crystallite size, and lattice strain have an important role in designing the state of art technology using different metal oxide nanostructures. Herein WO3 nanopowder was synthesized by facile precipitation method using WCl6 as precursor and water as a solvent. The effect of various parameters like urea (used as a capping agent), pH, temperature and different surfactants (CTAB (Hexadecyltrimethylammonium bromide) as cationic, SDS (Sodium dodecyl sulfate) as anionic and Tween20 as non-ionic has been studied on crystalline phase, crystallite size and lattice strain of WO3 nanopowder. The study of crystalline phase and crystallinity behavior was done by using x-ray diffraction spectroscopy. Crystallite size and lattice strain were calculated using two different ways i.e. by Debye Scherer’s formula and Williamson-Hall method via three different models: uniform deformation model, uniform deformation stress model, and uniform deformation energy density model. Surfactant-assisted WO3 nanostructure yield monoclinic phase at a higher temperature while urea capped samples give monoclinic phase at a lower temperature. Another phase orthorhombic tungstite (WO3.H2O) is observed to be at a lower urea concentration. Surfactant-assisted nanopowder has observed to show tungstite phase at a lower temperature. Besides this, an acidic environment is more suitable for the formation of orthorhombic tungstite nanopowder.

Study of phase behavior and Congo red dye partitioning in aqueous two-phase systems composed of hydrophilic alcohols (1-propanol/ 1-butanol) and sodium salts

ABSTRACTThe partitioning of the Congo red dye in ATPSs formed by alcohols (1-butanol, 1-propanol)/sodium salts was considered. Binodal and the LLE data were experimentally determined at 298.15 K. The salting-out abilities of the salts follow the order Na3C6H5O7 > NaH2PO4 > C2H3 O2Na. The phase-forming abilities of the alcohols follow the order: 1-butanol > 1-propanol. The four-parameter equation was applied to correlate the binodal curves data. Therefore, The Bancroft and Othmer-Tobias equations were used to prove the reliability of the corresponding LLE data. ATPS composed of 6.5% of 1-butanol and 20% of Na3C6H5O7 had the highest values of extraction by the yield of 98.54%.