Ideal Solution Theory Research Articles

Calculation of Carbon Dioxide Solubility in Liquefied Natural Gas

It is important to evaluate the solubility of solid carbon dioxide in liquefied natural gas for natural gas liquefaction at relatively high temperature. The regular solution method and the equations-of-state (EOS) are used to calculate the solubility of carbon dioxide in saturated liquid methane in this paper. The calculation results are compared with the experiment data, and it certifies that the EOS method can be recommended for this kind of solubility calculation. In addition, nitrogen and ethane are common components in natural gas. In this paper, PR EOS is selected to calculate the solubility of carbon dioxide in CH4+N2 and CH4+C2H6 mixtures. Results show that the solubility of carbon dioxide in liquid CH4+N2 mixtures increases with the addition of nitrogen content in the relatively low temperature region (lower than 155K). With the temperature increases, the solubility of carbon dioxide decreases with the increase of nitrogen content. While in liquid CH4+C2H6 mixtures, it increases with the increase of ethane content. liquid nitrogen, liquid oxygen or LNG. In 1940, Fedorova calculated the solubility of carbon dioxide in liquid oxygen and in liquid nitrogen according to ideal solution theory. At the same time, he did some experiments and found that the theoretical calculations are more than 100 times larger than the experimental values(7). In 1962, Davis et al performed a series of experiments on the methane-carbon dioxide system and got the solubility of carbon dioxide in methane at different temperatures(8). Most of these researchers are experts in the field of chemistry, who were focus on a variety of experimental methods of solubility determination. Li from Zhejiang University used the regular solution method and modified Scatchard-Hildebrand relation in her PhD thesis to calculate the solubility of carbon dioxide in liquid nitrogen and liquid oxygen, and obtained good results(9). As liquid methane is a cryogenic non-polar liquid similar with liquid nitrogen and liquid oxygen, similar method has been imitated in the calculation of the solubility of carbon dioxide in the saturated liquid methane in this paper. Additionally, simple cubic equations-of-state has been widely used in non-polar fluid phase equilibria calculations. In 2006, ZareNezhad and Eggeman(10) used PR EOS to predict CO2 freezing points of hydrocarbon liquid and vapor mixtures at cryogenic conditions of gas plants. The overall average absolute relative deviation between the experimental and predicted CO2 freezing temperatures for this binary system is 0.26%. So EOS method is selected for the solid-liquid phase equilibria calculation in this paper.

Thermodynamic properties of Al-Y system melts

The thermochemical properties of Al-Y melts were determined by isoperibolic calorimetry. It was established that the minimal value of integral mixing enthalpies is equal to −40.8 + 0.4 kJ/mol at 1770 K and xY = 0.41. The thermodynamic properties of liquid alloys were modeled by the developed procedure using the coordinates of a liquidus line in the phase diagram of the Al-Y system, and by the theory of ideal associated solutions. The component activities exhibit high negative deviations from the Raoult law. The Gibbs energies of mixing of Al-Y melts have a minimum of −30.6 kJ/mol at xY = 0.48.

Hydration of nonelectrolytes in binary aqueous solutions

Literature data on the thermodynamic properties of binary aqueous solutions of nonelectrolytes that show negative deviations from Raoult’s law due largely to the contribution of the hydration of the solute are briefly surveyed. Attention is focused on simulating the thermodynamic properties of solutions using equations of the cluster model. It is shown that the model is based on the assumption that there exists a distribution of stoichiometric hydrates over hydration numbers. In terms of the theory of ideal associated solutions, the equations for activity coefficients, osmotic coefficients, vapor pressure, and excess thermodynamic functions (volume, Gibbs energy, enthalpy, entropy) are obtained in analytical form. Basic parameters in the equations are the hydration numbers of the nonelectrolyte (the mathematical expectation of the distribution of hydrates) and the dispersions of the distribution. It is concluded that the model equations adequately describe the thermodynamic properties of a wide range of nonelectrolytes partly or completely soluble in water.

Vapor-phase adsorption of a mixture of benzene and chlorobenzene on the carbon adsorbent obtained by pyrolysis of hypercrosslinked polystyrene

Adsorption of a mixture of benzene and chlorobenzene from the gas phase on the carbon adsorbent D4609 (Purolite Int.) obtained by the pyrolysis of hypercrosslinked polystyrene was studied. The adsorption of the binary vapor mixture is satisfactorily described in terms of the theory of ideal adsorption solution. Specific features of the adsorption behavior of mixtures on this adsorbent are discussed.

A novel method for hybrid multiple attribute decision making

An approach based on 2-tuple is presented to solve the hybrid multiple attribute decision making problem with weight information unknown. First, transformation rules between linguistic variables and triangular fuzzy numbers, and distance between 2-tuple linguistics are defined, then the transformation method between 2-tuple linguistic and different forms of indicator values is given. Besides, according to grey incidence minimum deviation theory of positive ideal solution, the weights of indicators are determined, and then alternatives are ranked by 2-tuple linguistic weighting arithmetic average values. Finally, an illustrative example is given to demonstrate the procedure of the method and to compare with TOPSIS method to show the effectiveness and advantages of the presented method.

A thermochemical boundary layer at the base of Earth's outer core and independent estimate of core heat flux

SUMMARY Recent seismological observations suggest the existence of a ≈150-km-thick density-stratified layer with a P-wave velocity gradient that differs slightly from PREM. Such a structure can only be caused by a compositional gradient, effects of a slurry or temperature being too small and probably the wrong sign. We propose a stably stratified, variable concentration layer on the liquidus. Heat is transported by conduction down the liquidus while the light and heavy components migrate through the layer by a process akin to zone refining, similar to the one originally proposed by Braginsky. The layer remains static in a frame of reference moving upwards with the expanding inner core boundary. We determine the gradient using estimates of co, the concentration in the main body of the outer core, and cb, the concentration of the liquid at the inner core boundary. We determine the depression of the melting point and concentrations using ideal solution theory and seismologically determined density jumps at the inner core boundary. We suppose that co determines �ρ mod, the jump from normal mode eigenfrequencies that have long resolution lengths straddling the entire layer, and that cb determines �ρ bod, the jump determined from body waves, which have fine resolution. A simple calculation then yields the seismic, temperature, and concentration profiles within the layer. Comparison with the distance to the C-cusp of PKP and normal mode eigenfrequencies constrain the model. We explore a wide range of possible input parameters; many fail to predict sensible seismic properties and heat fluxes. A model with �ρ mod = 0.8 gm cc −1 , �ρ bod = 0.6 gm cc −1 , and layer thickness 200 km is consistent with the seismic observations and can power the geodynamo with a reasonable inner core heat flux of ≈2 TW and nominal inner core age of ≈1 Ga. It is quite remarkable and encouraging that a model based on direct seismic observations and simple chemistry can predict heat fluxes that are comparable with those derived from recent core thermal history calculations. The model also provides plausible explanations of the observed seismic layer and accounts for the discrepancy between estimates of the inner core density jumps derived from body waves and normal modes.

Theoretical Further Study on Synergisms of Binary Surfactant Mixtures in Aqueous Solution

By appointing the ideal mixture system of surfactants as the standard of comparison, synergisms in surface tension reduction efficiency and mixed micelle formation of binary surfactant mixtures in aqueous solution have been defined. Furthermore, based on the regular solution theory and the ideal solution theory, the conditions and the corresponding optimum point values of these two kinds of synergisms have been deduced. The conclusions have reasonably enlarged the scope of synergism theory proposed by Rosen and coworkers.

On the applicability of the theory of ideal adsorption solutions to equilibria in the N2-O2-zeolite NaX system

Experimental data on the joint adsorption of a nitrogen-oxygen gas mixture on zeolite NaX were analyzed using the theory of ideal adsorption solutions. Acceptable accuracy was obtained in calculations of binary isotherms from the adsorption isotherms of the pure gas mixture components. The calculated binary isotherms can be used to determine the parameters of the mathematical models of binary adsorption, for instance, competitive adsorption models.

Characterization and solubility measurement and prediction of selected arylamines in hexane, methanol and benzene

The solubility of nine arylamine molecules in benzene, methanol and hexane was measured. These molecules were: triphenylamine, N -(4-methyl phenyl) N , N bis phenyl amine, N -(3-methyl phenyl) N , N bis phenyl amine, N , N -bis(4-methyl phenyl) N -phenyl amine, N , N -bis(3-methyl phenyl) N -phenyl amine, tritolylamine ( N , N , N -tris-(4-methylphenyl)amine), N , N -bis-(4-methylphenyl)- N -(3-methylphenyl)amine, N , N -bis-(3-methylphenyl)- N -(4-methylphenyl)amine, and N , N , N -tris-(3-methylphenyl)amine. The solubility of these molecules was estimated using ideal solution theory, the Hildebrand equation, and UNIQUAC method. The ideal solution theory and the Hildebrand equation were not able to estimate solubility with high precision. However, UNIQUAC method was able to estimate the solubility with good accuracy. It was found that substitution of methyl group regardless of its number in aryl ring increases the solubility. In addition, meta-substitution always results in higher solubility regardless of the nature of the solvent. Physical properties, as well as electrochemical properties of these materials were also provided. Based on these data, the most promising candidates for device preparation should be: mTTA, TTA, mmmTTA, and mono-TPA. However, the only way to prove the above ranking would be to test the candidates in actual devices, which is outside the scope of this paper.

Thermodynamics of Liquid Alloys and Metastable Phase Transformations in the Copper - Titanium System

We have used solution calorimetry at temperatures of 1573 K and 1873 K over broad concentration ranges to study the mixing enthalpy of Cu - Ti liquid alloys. The molar mixing enthalpies of the system are significant negative values. We have established the temperature dependence of the molar mixing enthalpies of the system: there is an increase in their exothermicity as the temperature is lowered. The significant negative mixing enthalpies of the system allow us to conclude that the chemical bonds are localized in the studied melts and consequently associates form. We tested this conclusion within ideal associated solution theory, which describes well the results obtained with a set of CuTi and CuTi2 associates. Using the model obtained, we have calculated the excess thermodynamic functions of mixing (enthalpy, Gibbs free energy, heat capacity) for the liquid alloys. We estimated the Gibbs energies of fcc, bcc, and hcp solutions in the system by the CALPHAD method, using data from the initial sections of the phase diagrams and from the corresponding thermodynamic data. We have calculated the metastable phase equilibria between the limiting solid solutions and the liquid or supercooled liquid phase. It was shown that for the supercooled liquid and the amorphous phase, a broad concentration range of relative thermodynamic stability can be obtained. The concentration range of amorphization of Cu - Ti melts corresponds to the position of the metastable liquidus line and the T0 line at temperatures close to the temperature range of amorphous solidification.

Hygroscopic properties of levoglucosan and related organic compounds characteristic to biomass burning aerosol particles

Biomass burning, which is characterized by pyrolysis as well as vaporization and condensation of biomass constituents, is a significant source of atmospheric organic aerosols. In this study, hygroscopic properties of five organic compounds (levoglucosan, D‐glucose, and vanillic, syringic, and 4‐hydroxybenozoic acids), which are major pyrolysis products of wood, were measured using a tandem differential mobility analyzer. Levoglucosan, which is typically the most abundant species in wood burning aerosols, showed a significant hygroscopic growth for particles with a diameter of 100 nm. No efflorescence was observed under the measured relative humidity, and a supersaturated condition of levoglucosan‐water particles was observed. The growth factors of levoglucosan are 1.08, 1.18, 1.23, and 1.38 at relative humidity (RH) of 60, 80, 85, and 90%, respectively. The measured hygroscopic curves are in general consistent with those estimated from ideal solution theory and Uniquac Functional‐Group Activity Coefficient (UNIFAC) and Conductor‐Like Screening Model for Real Solvent (COSMO‐RS) methods. Significant hygroscopic growth was also observed for D‐glucose, whose growth factor is quite similar to that of levoglucosan. However, three model pyrolysis products of lignin (i.e., vanillic‐, syringic‐, and 4‐hydroxybenzoic acids) did not show any hygroscopic growth under the RH conditions up to 95%. On the basis of the organic composition of wood burning aerosols, the water absorption attributed to levoglucosan in wood burning aerosols is calculated to be up to 30% of the organic mass at 90% RH. This study demonstrates that oxygenated organics emitted from biomass burning could significantly enhance the hygroscopic properties of atmospheric aerosols.

Where do the H atoms reside in PdH x systems?

We present an ab initio density-functional theory study of PdH x systems. We evaluated the total energy of PdH x systems with the H atoms occupying interstitial (octahedral and tetrahedral) sites of a Pd supercell, allowing for the relaxation of the coordinates and supercell dimensions. The majority of our calculations were based on supercells consisting of four Pd atoms, and up to four H atoms, covering the range from x = 0.25 to x = 1. In addition some larger calculations are reported. In order to compare the relative stability of systems at different values of x (at fixed pressure and temperature T = P = 0), we computed the enthalpy of formation ΔH f (x) of the (non)stoichiometric systems. In the regime x = 0 → 1, the ΔH f (x) decrease in a manner indicative of the existence of attractive interactions between the dissolved H atoms. Ideal-solution theory cannot be applied to this system. Furthermore, we find that tetrahedral occupation is favoured over octahedral occupation at high x, leading to the formation of a zincblende structure at x = 1. A preliminary vibrational analysis of normal modes has been performed. Inclusion of vibrational zero-point energies in a harmonic approximation leads us to conclude, tentatively, that the observed stability of octahedral site occupation is due to more favourable zero-point energies of the H atoms in those sites. The results indicate that a proper understanding of this system must take into account the quantum nature of the dissolved hydrogen.

Surface freezing in n-alkane solutions: the relation to bulk phases.

Surface freezing (SF) was investigated in tricosane-dodecane alkane solutions as a function of temperature (T) and molar concentration of tricosane (phi), using surface tension and synchrotron x-ray surface diffraction techniques. A crystalline SF monolayer, having a rotator R(II) structure, was found to exist for 35 degrees C</=T</=50 degrees C and 0.3</=phi</=1. The extended temperature range allowed to determine the linear-expansion coefficient of the SF monolayer, (dd/dT)/d=6.5 x 10(-4) degrees C-1. A simple thermodynamical model based on the theory of ideal solutions is shown to account well for the phi dependence of the SF temperature T(s)(phi). The study shows that the temperature range of existence of the surface frozen layer at each phi, the phi range over which SF is observed, and the bulk solidification behavior, are intimately related. All are determined by the rotator-liquid dissolution line T(dR)(phi).

Thermal Analysis of Solid-Solid Interactions in Binary Mixtures of Alkylcyclohexanes Using DSC

Differential scanning calorimetry (DSC) was used to construct phase diagrams of binary mixtures of alkylcyclohexanes and to characterize metastable phases formed in the binary mixtures. The experimentally measured liquidus curves were compared to the liquidus curves calculated using ideal solution theory. The measured phase diagrams of pentadecylcyclohexane/nonadecylcyclohexane and octadecylcyclohexane/nonadecylcyclohexane binary mixtures are consistent with theoretical phase diagrams constructed based on the assumption that these mixtures form eutectic systems. It was also observed that a metastable phase formed in some binary mixtures of pentadecylcyclohexane/nonadecylcyclohexane under fast cooling conditions. It is hypothesized that this metastable phase recrystallizes into the eutectic phase upon heating.

Thermodynamics of mixtures with strongly negative deviations from Raoult's law Part 2. Application of the DISQUAC model to mixtures of CHCl3 or CH2Cl2 with oxaalkanes. Comparison with Dortmund UNIFAC results

Binary mixtures of linear and cyclic oxaalkanes and CHCl3 or CH2Cl2 are characterized in the framework of the DISQUAC model. The interaction parameters for the corresponding O/Cl contacts are reported. The enthalpic quasichemical interchange coefficients are negative, as in other mixtures which also show strong negative deviations from Raoult's law. There are proximity effects on both dispersive and quasichemical interaction parameters of diethers and acetals. DISQUAC represents fairly well the thermodynamic properties examined: vapor–liquid equilibria (VLE), molar excess enthalpies (HE), molar excess heat capacities at constant pressure (CpE) or natural logarithms of activity coefficients at infinite dilution (ln γi∞). DISQUAC provides much better results than the Dortmund version of UNIFAC using the published geometrical and interaction parameters. From this comparison, it seems that one should distinguish, at least, between linear monoethers, polyethers or acetals. Each cyclic molecule should be treated separately. A short comparison between DISQUAC and the ideal associated solution theory is also included. Both models yield similar results.

Influence of solvent content on phase‐transition temperatures of oil sedimen and solution viscosity in acetone/canola oil systems

AbstractThe effect of acetone on phase transition behavior of sediment in canola oil was studied by differential scanning calorimetry under dynamic heating/cooling regimes. The melting temperature of sediment decreased with an increase in the solvent content of canola oil, suggesting an increase in the solubility of sediment in the oil solution. The crystallization of sediment in oil solution was facilitated by acetone, as indicated by the increase in the sediment crystallization temperature. Acetone dramatically reduced the viscosity of canola oil, particularly in the first 30% addition. The reduction of viscosity was far less with further addition of acetone. These results suggested that the optimum range of acetone content needed for sediment precipitation in canola oil would be in the range of 30–40%. A linear relationship was found between the density of canola oil and temperature. The influence of solvent on the density of canola oil/acetone solution can be accounted for by the mixing theory of ideal solutions, whereas the effect of temperature on the dynamic viscosity of oil solution is best described by a modified Arrhenius equation.

Chloride Ion Barrier Properties of Small Electric Fields in the Protection of Steel in Concrete

Abstract Analysis of the Nernst-Plank relation suggested that a relatively small voltage drop would maintain a significant chloride concentration difference across an ideal electrolyte. This effect was used as the basis for a possible criterion for the protection of steel in concrete in which the chloride concentration at the steel is maintained at a level below that necessary to cause passive film breakdown. The applicability of ideal solution theory to the electrolyte in a porous cement matrix was investigated by driving chloride ions against a concentration gradient across a cement mortar disc using a small applied potential difference. Results indicated the potential difference was an effective barrier to chloride ions and that the theory presented can be used in the design of an active chloride barrier. This protective effect can be monitored by determining the voltage drop through the concrete between an installed anode and the protected steel. However, caution should be exercised when dealing with ...

The effect of a potential-sensitive barbituric acid molecular probe on the thermal phase transition properties of multilamellar 1,2-dimyristoyl- sn-glycero-3-phosphocholine suspensions

The interaction of the extrinsic, potential-sensitive probe diBa-C 2-(5) with 1,2 dimyristoyl- sn-glycero-3-phosphocholine (DMPC) in the form of unilamellar vesicles or as multilamellar suspensions has been characterized by probe-membrane binding studies and differential scanning calorimetry. The presence of diBa-C 2-(5) in DMPC suspensions lowers the temperature at the midpoint of the gel-to-liquid-crystalline phase transition T m by a maximal 0.15°C. The enthalpy of the gel-to-liquid-crystalline phase transition is reduced by a maximal 4%, whereas that of the pre-transition is unaffected by the presence of 5 mol% diBa-C 2-(5). The cooperativity of the gel-to-liquid-crystalline phase transition is reduced by a maximal 35%. When present at a concentration of 5 mol%, this indicator causes virtually no change in the pre-transition cooperativity. The diBa-C 2-(5)/DMPC system can be described by the ideal solution theory when the probe is present at a concentration of ≤0.2 mol%. Non-ideal behavior of the diBa-C 2-(5)/DMPC system is observed at concentrations >0.2 mol% probe. DiBa-C 2-(5) mildly perturbs the membrane in comparison to the effects of most other potential-sensitive probes, and is probably located at or near the surface of the bilayer.

Ellipsometry Studies of the Self-Assembly of Nonionic Surfactants at the Silica-Water Interface: Kinetic Aspects

The nature of layers of a series of poly(ethy1ene glycol) monoalkyl ethers (C,,Em) adsorbed on silica surfaces has been systematically investigated by means of null ellipsometry. The results show that adsorption remains low until a well-defined concentration ((=0.6-0.9)cmc) is exceeded. Then, as surfactants in the interfacial region start to self-absemble, it increases abruptly and plateau adsorption is generally observed prior to the cmc. The normal extension of the interfacial aggregates is relatively constant from intermediate to high surface coverage. Increasing the ethylene oxide to hydrocarbon ratio results in a decreased adsorption. The mean optical thickness, on the other hand, is relatively independent of the number of ethylene oxide groups in the surfactant but almost linearly dependent on the length of the hydrocarbon tail. The values obtained for these parameters suggest that the adsorbed layer is built up of discrete surface aggregates, or micelles, with dimensions resembling those observed in bulk solution. A more refined optical model of the adsorbed layer confirms the notion of surface micelles growing with increasing hydrocarbon content. It also points out that the extension of the surface micelles is slightly larger than the measured mean optical thickness. In addition to studies of neat CS, surfactants, we also examine the adsorption of mixed surfactant systems. Changes observed in adsorption on altering the bulk ratio of two surfactants are well correlated to the bulk micellar surfactant ratio calculated by ideal solution theory.

Entropic Contributions to Free Energies of Solvation

Two alternative ways to treat the entropy of solution in the molecular thermodynamics of liquid-phase solutions have proved useful under various circumstances. The first is the ideal solution theory in which the entropic effects are the same as for mixing ideal gases. The second is the theory of Flory and Huggins which is most appropriate for nondilute solutions of chain molecules in small solvents. The two theories are compared for their ability to describe solutions of alkanes, both straight-chain and branched, in aqueous solution. The alkanes provide an especially appropriate testing field because electrostatic effects are minimal, and it is reasonable to assume that the solvation free energy consists almost entirely of entropic contributions and first-hydration-shell effects