Solid-liquid Equilibrium Temperature Research Articles

Solid-Liquid Equilibrium Study of Binary System Saturated Fatty Acid in Short Chain Alcohols

Unsaturated fatty acids are potential to be used for preventing degenerative diseases and developing brain function in babies. Separation of unsaturated fatty acids from saturated fatty acids efficiently achieved by urea complexation fractionation method. It is considered to be the simplest, most efficient, and lowest cost method. This study aimed to optimize urea complexation for increasing PUFA concentrations by determining solid-liquid equilibrium data of saturated fatty acids in short chain alcohols. In this study, there were two types of short chain alcohol, methanol and ethanol, in various concentrations (99,7%; 95%; 88%; 76% w/w) towards the solubility of saturated fatty acids, palmitic and stearic acid (PA and SA). PA and SA dissolved in various concentration of methanol and ethanol to get homogeneous solutions. When solid SFA disappeared by heating the solution, or first formed by cooling the solution, the temperature was determined as the solid-liquid equilibrium temperature. The results showed that the best composition of solvent within high solubility level is ethanol 95% and methanol 99,7% over palmitic acid because it can dissolve at room temperature and below 0.01 mole fraction.

Morphology and Composition of Inclusions in Si-Mn Deoxidized Steel at the Solid-liquid Equilibrium Temperature

Morphology and Composition of Inclusions in Si-Mn Deoxidized Steel at the Solid-liquid Equilibrium Temperature

Solid-fluid equilibrium measurements of benzene in methane and implications for freeze-out at LNG conditions

Information about the solubility of benzene in light hydrocarbons is particularly important for the prediction of freeze-out risk in LNG production. Engineering models developed to predict this risk need to be tested against high quality experimental data covering a range of conditions to assess their validity. A visual high pressure sapphire cell, housed in a specialized cryogenic environmental chamber, was employed to measure the melting temperature of methane + benzene binary systems at temperatures from 120 K, pressures up to 22 MPa, and benzene concentrations ranging from 120 to 1012 parts per million (ppm) by mole. The results obtained were compared with literature data and the predictions of the thermodynamic model implemented in the software package ThermoFAST. These comparisons reveal that the literature data are in fact consistent with each other, and with the measurements and predictions made in this work, within their experimental scatter. ThermoFAST was able to represent the melting temperatures obtained for benzene concentrations of 1012 and 199 ppm with r.m.s deviations of 0.7 and 3.4 K, respectively. At 120 ppm and 6.3 MPa, the measured solid-liquid equilibrium (SLE) temperature deviated from the ThermoFAST prediction by less than 2 K. However, at the higher temperature conditions representative of solid vapour equilibrium (SVE), the data measured for mixtures with concentrations at 199 and 750 ppm benzene deviated from the model predictions by up to 5 K.

Morphology and Composition of Inclusions in Si–Mn Deoxidized Steel at the Solid-Liquid Equilibrium Temperature

Morphology and composition of inclusions change with temperature. However, besides the temperature conditions during steelmaking or continuous casting, other factors contributing to changes in the morphology and composition of inclusions during solidification are still unknown. In this study, the formation of complex inclusions in Si–Mn deoxidized steel after isothermal holding at the solid-liquid equilibrium temperature (TS) was investigated.

Calorimetry Technique for Observing the Evolution of Dispersed Droplets of Concentrated Water-in-Oil (W/O) Emulsion during Preparation, Storage and Destabilization

In this work, the evolution of dispersed droplets in a water-in-oil (W/O) emulsion during formation, storage, and destabilization was observed using a calorimetry technique. The emulsion was prepared by dispersing drop by drop an aqueous phase into an oil continuous phase at room temperature using a rotor-stator homogenizer. The evolution of droplets during (1) preparation; (2) storage; and (3) destabilization was observed using differential scanning calorimetry (DSC). The samples were gently cooled-down below its solid-liquid equilibrium temperature then heated back above the melting point to determine its freezing temperature. The energy released during the process was recorded in order to get information about the water droplet dispersion state. The mean droplet size distribution of the sample emulsion was correlated to its freezing temperature and the morphology was followed by optical microscopy. The results indicated that the calorimetry technique is so far a very good technique of characterization concentrated W/O emulsions.

The importance of supersaturation on determining the solid-liquid equilibrium temperature of waxy oils

Crystallization is a process where an ordered solid structure is formed from a disordered phase. This event is divided in two main stages, namely nucleation and crystals growth. As paraffin nucleation is a stochastic process, a supercooling is needed to initiate the process. In other words, the beginning of crystal precipitation does not coincide with the highest thermodynamic solid-liquid equilibrium temperature. Therefore, during the cooling it is required that the fluid reaches a certain temperature below saturation, i.e., a metastable state, to initiate the crystal nucleation process. The difference between the saturation temperature and the crystallization temperature is called degree of supercooling. As this metastable condition may exist during not only the crystallization but also the dissolution of crystals, this work proposes a procedure to determine consistently the highest solid-liquid thermodynamic equilibrium temperature by using the results of rheometer and DSC experiments. It can be anticipated that the proposed protocol states that the highest solid-liquid thermodynamic equilibrium temperature is considered to approach the dissolution temperature when the material is heated at a very low heating rate.

Solid-liquid equilibria of eicosane, tetracosane or biphenyl + 1-octadecanol, or + 1-eicosanol mixtures

A differential scanning calorimetric (DSC) technique has been used to obtain solid-liquid equilibrium temperatures for n-C20, or n-C24, or biphenyl + 1-octadecanol, or + 1-eicosanol mixtures. All the systems show a simple eutectic point. The final composition of these points is determined on the basis of the Tamman plots using values of the eutectic heat and of the heat of melting, which are also reported. Deviations of activity coefficients (γ) from unity for the mentioned mixtures and for the systems n-C24 or n-C28 + cyclododecane, or + cyclododecanol and for dodecane + cyclohexanol are discussed in terms of the alcohol self-association and size effects. Mixtures with alkanols show positive (γ− 1) values. Such differences are larger for the cyclohexanol system, as this is the most self-associated alcohol considered. Size effects lead to slightly negative (γ− 1) values for cyclododecane solutions. Using the regressed parameters, DISQUAC provides a good description of the phase diagrams for the mixtures under consideration and improves results from the UNIFAC (Dortmund) model. The influence of size effects on the DISQUAC interaction parameters is discussed.

Thermal analysis of molten ternary lithium-sodium-potassium nitrates

The pre-melting, melting and degradation events of a ternary LiNO3-NaNO3-KNO3 (29.63-13.23-57.14 wt%) salt have been investigated using simultaneous thermal analyzer (STA) for potential use as a heat transfer and storage fluid (HTF). This composition was selected based on the thermochemical calculation using the FactSage 7.0 to find the lowest solid-liquid equilibrium temperature. The melting point obtained from STA (122.8 °C) indicated a good agreement with the theoretical value determined by FactSage (120.8 °C), which is 100 °C less compared to binary NaNO3:KNO3 solar salt. The salt was heated from 50 to 800 °C in 3 atm (argon, air, and O2) at three scanning rates (2.5, 5 and 10 °C/min) to investigate its decomposition limits. At 10 °C/min scanning rate the salt started to degrade rapidly at 545 °C in argon, 571 °C in air and 600 °C in oxygen, respectively. In argon at a higher heating rate (10 °C/min), the salt degradation was delayed by 42 °C. The main gaseous products of decomposition were found to be O2, N2, NO, N2O and NO2. After melting, at higher temperature the evolution of O2 and NO indicated that primary and secondary decomposition reactions are concurrent and overlapping. The heating-cooling rates have low effect on the onset of melting and offset freezing temperatures but, have an effect on peaks height, peaks width, and transition enthalpies. The α/β transition (75 °C peak temperature) during cooling only appeared at the 1 °C/min cooling rate. The ternary salt offers 70 °C greater operating temperature range compared to binary solar salt in argon. At a higher partial pressure of O2, decomposition was delayed by 55 °C (at 10 °C/min), which could be used to increase the power cycle efficiency of solar electricity generation.

Solid-liquid equilibria of indole binary systems

Solid-liquid equilibrium temperatures, obtained using a differential scanning calorimetry (DSC) technique, are reported for indole(1)+n-C20(2), or +n-C24(2), or +n-C50(2) systems. Values of the eutectic heat and of the heat of melting needed to determine the final composition of the eutectic points on the basis of the Tamman plots are also given. At x1>x1eu (eutectic mole fraction), the mixtures with n-C20, or n-C24 show positive deviations from the Raoult́s law, which reveal the existence of indole-indole interactions in that range of concentration. At x1<x1eu, the systems show an ideal behaviour. The mixture with n-C50 is characterized by negative deviations from the Raoult’s law due to the very different size of the mixture components. Systems formed by indole and n-alkane, aromatic compound or alkyl-naphthalene have been investigated by means of the DISQUAC model. The interaction parameters for the aliphatic/amine contacts in the studied mixtures are reported. DISQUAC improves results from the ideal solubility model.

Solid–liquid equilibria of biphenyl binary systems

Solid–liquid equilibrium temperatures, obtained by means of a differential scanning calorimetry (DSC) technique, are reported for biphenyl+n-C21, or +n-C31, or +n-C41 systems. Biphenyl+alkane, or +heterocyclic compound (diphenyl ether, dibenzofuran, indole, diphenylamine, 1-octadecanol or octadecanoic acid) have been investigated using DISQUAC and the ideal solubility model. This model provides good results for alkane solutions whose components which largely differ in size. Interactional effects are relevant in solutions with heptane, octadecane or mixtures involving dibenzofuran, indole, 1-octadecanol or octadecanoic acid.

Self-instability of finite sized solid-liquid interfaces.

In solid-liquid systems, macroscopic solids lose their equilibrium and melt in a manner that results in overall movement of the solid-liquid interface. This phenomenon occurs when they are subjected to temperature gradients or external stress, for example. However, many experiments suggest that the melting of nano- and micro-sized metallic nuclei follows a different process not described by traditional melting theory. In this paper, we demonstrate through simulation that the melting of solid nuclei of these sizes occurs via random breaches at the interfaces. Moreover, this breaching process occurs at the exact solid-liquid equilibrium temperature and in the absence of any external disturbance, which suggests the name “self-instability” for this melting process. We attribute this spontaneous instability to the curvature of the samples; based on the relationship between the sample’s instability and its curvature, we propose a destabilizing model for small systems. This model fits well with experimental results and leads to new insights into the instability behavior of small-sized systems; these insights have broad implications for research topics ranging from dendrite self-fragmentation to nanoparticle instability.

Thermochemical and vapor pressure behavior of anthracene and brominated anthracene mixtures

The present work concerns the thermochemical and vapor pressure behavior of the anthracene (1)+2-bromoanthracene (2) and anthracene (1)+9-bromoanthracene (3) systems. Solid–liquid equilibrium temperature and differential scanning calorimetry studies indicate the existence of a minimum melting solid state near an equilibrium temperature of 477.65K at x1=0.74 for the (1)+(2) system. Additionally, solid–vapor equilibrium studies for the (1)+(2) system show that the vapor pressure of the mixtures depends on composition, but does not follow ideal Raoult's law behavior. The (1)+(3) system behaves differently from the (1)+(2) system. The (1)+(3) system has a solid solution like phase diagram. The system consists of two phases, an anthracene like phase and a 9-bromoanthracene like phase, while (1)+(2) mixtures only form a single phase. Moreover, experimental studies of the two systems suggest that the (1)+(2) system is in a thermodynamically lower energy state than the (1)+(3) system.

Ice slurry crystallization based on kinetic phase-change modeling

Most crystallization models for ice slurries are based on the equilibrium thermodynamic approach, an assumption that is not made a priori here. We present results of simulations grounded on classical nucleation theory and crystal growth included in global Nakamura-type kinetics coupled with the one-dimensional nonlinear heat equation, another way to model the phase change. The work focuses on ice slurry crystallization using kinetic tools integrating the temperature glide for mixtures (i.e., the solid–liquid equilibrium temperature Tf depends on the residual fluid’s solute concentration) without any equilibrium assumption. The heat-transfer phenomena in the experimental device are first determined, and then the parameters of kinetic function of crystallization are identified for pure water samples and then for 15 wt% monopropylene glycol (MPG) – water mixtures. An inverse method is implemented with a genetic algorithm to determine the kinetic parameters.

Automated apparatus for the rapid determination of liquid–liquid and solid–liquid phase transitions

An automated apparatus developed for the determination of liquid–liquid and solid–liquid equilibrium temperatures with a resolution of 1 mK and a traceable accuracy of 0.01 K is described. The amount of light transmitted through six sample cells placed in a computer controlled thermostat is recorded at heating or cooling rates from 0.075 to 15 K h −1. The construction does not require expensive optic equipment like lasers, glass fibre optics or photomultipliers, but is based on light emitting diodes (LED) as light sources and light dependent resistors (LDR) or photodiodes as detectors. As shown by the discussed examples, the instrument has a wide range of possible applications from the investigation of simple one-component and binary systems to the study of the complicated phase behavior of surfactant solutions.

Thermodynamics of mixtures containing organic carbonates: Part XIII. Solid–liquid equilibria of long-chain 1-alkanol + dimethyl or diethyl carbonate systems: DISQUAC and ERAS analysis of the hydroxyl/carbonate interactions

Solid–liquid equilibrium temperatures for systems of 1-tetradecanol, 1-hexadecanol, 1-octadecanol, or 1-icosanol with dimethyl or diethyl carbonate have been measured using a dynamic method. The alcohols present two first order transitions. 1-Alkanols+linear organic carbonates mixtures are studied using DISQUAC and ERAS models. The corresponding interaction parameters are reported. They behave similarly in both models. In DISQUAC, the QUAC parameters are independent of the mixture compounds, as in many other alcoholic solutions previously analyzed. The DIS parameters increase with the size of the alcohol. They remain constant for the longer alcohols. In ERAS, Δv AB ∗ is independent of the mixture components, while Δh AB ∗ depends only on the carbonate. DISQUAC yields a consistent description of the thermodynamic properties examined: vapor–liquid equilibria molar excess Gibbs energies, Solid–liquid equilibria and molar excess enthalpies. DISQUAC improves ERAS results on excess molar enthalpies, as the calculated curves using ERAS are shifted to the region of low concentration in alcohol. This means that, in terms of ERAS, the contribution to the excess molar enthalpy from the self-association of the alcohol is overestimated. Molar excess volumes are well represented by ERAS. From the analysis of the excess molar enthalpy curves, it is concluded that they are determined mainly by dipolar interactions between carbonate molecules. Excess molar volumes are relatively low indicating strong structural effects.

Fundamental Study of the Phase Behavior of Wash Oil with Diphenyl Ether

Diphenyl ether is a potential modifier to decrease the melting temperatures of wash oils and thus to prevent solid formation from the recycled stream in an aromatics removal process. Fundamental study of the solid-liquid equilibria for the related mixtures was undertaken in the present work. Solid-liquid equilibrium data were measured for binary and multicomponent mixtures containing model compounds of wash oils (acenaphthene, dibenzofuran, fluorene, and phenanthrene) and diphenyl ether. The results showed that adding diphenyl ether substantially lowered the melting points of wash oils. A series of batch distillations with various initial feeds were also made to investigate further the property changes of the wash oils before and after recovery. It was found that diphenyl ether could still remain in the residues (the recovered wash oils) and changes in the melting temperature of oils were minor. These low-melting wash oils can be recycled directly to benzol scrubber for reuse. The binary solid-liquid equilibrium data were correlated with the NRTL model. The solution model with the determined parameters is capable of predicting the solid-liquid equilibrium temperatures of the pseudo-binary (multicomponent) system to an AAD of 0.3%.

Comparison Of Air‐blast And Pressure Shift Freezing On Norway Lobster Quality

ABSTRACT:Pressure shift freezing (PSF, 200 MPa, –18 °C) of whole Norway lobster was compared with air‐blast freezing and with pressurized samples (200 MPa, 5 °C) without freezing for its effect on the quality in texture, structure, water, and salt soluble protein extractabilities. For the pressurized Norway lobster meat either with PSF or without freezing, toughness increased while salt soluble protein extractability decreased. Conversely, air‐blast freezing did not affect the textural quality of the meat. Scanning electron micrographs showed that PSF yielded smaller ice crystals than air‐blast freezing.

Thermodynamics of branched alcohols: II. Solid–liquid equilibria for systems containing tert-butanol and long-chain n-alkanes. Experimental results and comparison with DISQUAC predictions

Solid–liquid equilibrium temperatures for tert-butanol+ n-alkanes (C 18, C 19, C 20, C 21, C 22, C 23, C 24, C 25, C 26, C 28) systems have been measured by a dynamic method from 298.15 K to the melting point of the alkane. All the systems present an eutectic point at very low concentration of the alcohol. A first-order transition was observed for many of the n-alkanes considered. The experimental values are compared with those given by the DISQUAC model using the interaction parameters previously determined on the basis of vapor–liquid equilibria, VLE, and molar excess enthalpies, H E, of systems containing the lower n-alkanes ( n-C 6, n-C 7). Calculations were developed taking into account the solid–solid transition of the alkanes. The mean relative standard deviation for the equilibrium temperatures is 0.0073. Differences between experimental data and calculated results for SLE and H E are analysed in terms of the Patterson effect. The possibility of improving predictions by modifying only the third dispersive interchange coefficient is discussed. Two values for this parameter are proposed depending on n, hereafter the number of C atoms in the n-alkane ( n≤8 and n≥9). In this way, the variation with the temperature of H E is better represented by the model for those systems including the longer n-alkanes. Predictions on SLE remain unchanged, because they depend essentially on the first interchange coefficients when the range of temperature considered, as in this case, is rather narrow.

Solid-liquid equilibria for systems containing long-chain 1-alkanols III. Experimental data for 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-icosanol + 1-butanol, 1-hexanol, 1-octanol or 1-decanol mixtures. Characterization in terms of DISQUAC

Solid-liquid equilibrium temperatures for 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-icosanol + 1-butanol, 1-hexanol, 1-octanol or 1-decanol systems have been measured by a dynamic method from 275 K to the melting point of the long-chain 1-alkanol. An eutectic point was encountered for those mixtures containing 1-decanol. However, first-order transitions between different crystal forms (α, β, γ) of the long-chain 1-alkanols were observed. It was noted that these solid-solid transitions are very stable in alcohols unlike in hydrocarbons or other solvents. The solubility of a given long-chain 1-alkanol is nearly the same in all alcohols tested from 1-butanol to 1-decanol. Only below the second phase transition point does the solubility change, increasing with the molecular weight of the shorter alcohol. The hydroxyl/hydroxyl interactions present in the investigated systems were characterized in terms of DISQUAC using dispersive interchange coefficients for such contacts. Calculations were developed taking into account the solid-solid transitions of the 1-alkanols. The mean relative standard deviations for the equilibrium temperatures are 0.006 for mixtures with an alcohol in the absence of 1-icosanol; and the experimental data are fairly well represented by ideal solubility curves. For mixtures including 1-icosanol, the mean relative standard deviations are 0.021, as the model cannot reproduce, using the proposed interaction parameters, their negative deviations from Raoult's law.

Solid-liquid equilibria for systems containing long-chain 1-alkanols. II. Experimental data for 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-eicosanol + CCl 4 or + cyclohexane mixtures. Characterization in terms of DISQUAC

Solid-liquid equilibrium (SLE) temperatures for 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-eicosanol + CCl 4 mixtures and for 1-dodecanol or 1-tetradecanol + cyclohexane systems have been measured by a dynamic method between 273 K to the melting point of the alcohol. First order transitions between different crystal forms (α, β, γ) of the alcohols were observed. The solid-solid transitions of these long-chain alcohols changed with the solvent as result of solute-solvent interactions. This behaviour is also encountered in many other systems. The hydroxyl/cyclohexane and hydroxy/CCl 4 interactions present in the investigated systems were characterized in terms of DISQUAC, reporting the interchange coefficients for such contacts. It is remarkable that these interchange coefficients remain constant for a given alcohol: from 1-octadecanol for mixtures with cyclohexane, and from 1-hexadecanol for those systems containing CCl 4. Calculations were developed taking into account the solid-solid transitions of the 1-alkanols. This is important because of the large value of the molar heat of the α → β transition. For mixtures containing alcohols other than 1-eicosanol the relative standard deviations for the equilibrium temperatures were less than 0.009. For mixtures containing 1-eicosanol the relative standard deviations were close to 0.020, because the model cannot, using the proposed interaction parameters, reproduce their negative deviations from Raoult's law.