Non-equilibrium thermodynamics of boundary conditions for rarefied gases and related phenomena

The interrelation of the kinetic theory and non-equilibrium thermodynamics is discussed. A procedure for deriving the boundary conditions for slightly rarefied gases is outlined. The entropy productions from the processes associated with the non-uniform gas flow in channels with mobile walls and with the presence of an arbitrary geometric particle in non-uniform fluid are found. Using the entropy productions, the phenomenological equations are obtained. New phenomena predicted on the basis of these equations, and their experimental testing are discussed.     

Molecular thermodynamics of fluid mixtures containing molecules differing in size and potential energy

Recent computer-simulation work by Shing and Gubbins (1983) for binary mixtures has shown that common semiempirical models (van der Waals n-fluid models) are in error when the molecules of the two components differ appreciably in size; the error is most severe in the dilute region. While perturbation theories are much better, they (like computer simulations) are not as yet useful for engineering work because of prohibitive computer requirements.This work proposes an algebraic expression for the Helmholtz energy of a mixture which gives results in very good agreement with those reported by Shing and Gubbins. This expression, using the local-composition concept, is based on a simplified but realistic picture of a fluid mixture: short-range order and long-range disorder. The proposed expression uses the Mansoori-Carnahan-Starling-Leland equation for the contribution of repulsive forces. For the contribution of attractive forces, it uses a new expression based on not one but several radii for the first-neighbor shell, one radius for each component.With reasonable simplifications, the resulting equation for the Helmholtz energy indicates that the van der Waals “constant” a is a strict quadratic function of mole fraction only at very low densities; at advanced densities, there are small deviations from the quadratic mixing rule. For practical calculations, the computer requirements are nearly the same as those for conventional engineering models.     

Wetting criteria for the applicability of membrane distillation

Membrane distillation can only be applied on liquid mixtures which do not wet a microporous hydrophobic membrane. Solutions of inorganic material in water have such high values of surface tension (γ_L⩾72x10⁻³ N/m) that the non-wetting condition is fulfilled for a number of hydrophobic membranes. As soon as organic solutes are present in the solution, the surface tensionγ_L will be lowered, and if the concentration of organic material becomes too high, wetting of the membrane will occur. By means of theoretical considerations a critical solute concentration or surface tension at which a homogeneous smooth material will be wetted (gq < 90/deg) can be calculated. For a (micro)porous membranes no such theoretical relation can be derived. Therefore, a simple experimental method is described to measure the maximum allowable concentration for a (micro)porous membrane. On the basis of these measurements, the maximum allowable concentration under process conditions can be determined.     

Clathrate thermodynamics for the unstable host framework

We have introduced the concept of clathrates whose empty host framework is unstable. In contrast to the Van der Waals theory, according to which the empty host framework is metastable, we believe it to become metastable when, in the cellular clathrates, certain type of cavities are fully occupied or, in the channel clathrates, the guest molecules are closely packed. The free energy of the channel and cellular types of clathrates has been determined using statistical thermodynamics methods. The obtained chemical potentials allowed us to describe the equilibrium of the clathrate with the stable host -phase and the gaseous guest phase. For the cellular clathrates the equations have been obtained determining the dependence of the degree of filling of small cavities upon temperature and the gaseous phase pressure. In the case of the channel clathrates the set of equations on the composition and parameter of the orientational ordering is found. These equations enable us to describe quantitatively compressed state of the guest molecules in the channel and to find temperatures of orientational ordering.     

Predictive thermodynamics for condensed phases

Thermodynamic information is central to assessment of the stability and reactivity of materials. However, because of both the demanding nature of experimental thermodynamics and the virtually unlimited number of conceivable compounds, experimental data is often unavailable or, for hypothetical materials, necessarily impossible to obtain. We describe simple procedures for thermodynamic prediction for condensed phases, both ionic and organic covalent, principally via formula unit volumes (or density); our volume-based approach (VBT) provides a new thermodynamic tool for such assessment. These methods, being independent of detailed knowledge of crystal structures, are applicable to liquids and amorphous materials as well as to crystalline solids. Examples of their use are provided.     

On the applicability of the first-order equation for the reactions of solids

It is suggested that besides its traditional application to describe random nucleation, the first-order equation F1 can be used for the diffusion kinetics of gas-solid small particles reactions.

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, F1 - - .

     

The applicability of radiotracers for the investigation of the distillation of hydrocarbons

The use of radioactive tracers provide valuable methods for the investigation of distillation processes and have been applied to determine the characteristics of material streams, the dynamics of flowing phases and the compositions in various parts of the distillation equipment. A method is proposed for testing individual radiotracers employed for the investigation of the distillation of hydrocarbons. The method consists in laboratory-scale distillation of a tracer together with a multicomponent hydrocarbon mixture, namely a gasoline fraction. The purification efficiency, distillation characteristics, and effective radiochemical purity of several tracers (reactor activated bromobenzene and synthesized C₃H₇ ⁸²Br, C₄H₉ ⁸²Br, C₅H₁₁ ⁸²Br) have been investigated. The distillation characteristics of bromohydrocarbons labelled with⁸²Br and selected hydrocarbons tagged with¹⁴C (benzene and cumene) have been compared. The radiotracers investigated were employed for the determination of the hydrodynamic parameters of hydrocarbon distillation in laboratory packed columns and a commercial distillation tower.     

Molecular thermodynamics approach for polymer-polymer miscibility

We extended the previous lattice model for polymer solution systems to binary polymer blend systems. Based on Müller’s Monte-Carlo simulation data for symmetric system (r₁ = 32 and r₂ = 32), the energy of mixing is correlated as a function of temperature and composition using an empirical expression. In addition, we introduce new universal functions which reflect the characteristics of polymer-polymer miscibility behaviors. In associated blend systems, specific interactions between polymer segments are considered by using a secondary lattice. Using only one or two adjustable parameters, the proposed model satisfactory correlates the experimental data of real polymer blend systems with greater accuracy than those of other models.     

On the applicability of CNDO indices for the prediction of chemical reactivity

A series of CNDO/2 molecular orbital properties were evaluated to determine their utility in parameterizing chemical reactivities. Some of these indices were used previously for only electron methods and were extended here to include the framework. Theoretical rationales were given for this extension to the semi-empirical all valence electron methods. Four systems, the aromatic hydrocarbons, the benzene derivatives, the substituted benzoic acids, and the substituted phenyl amines, were studied to test how well these indices can parameterize chemical reactivities. This study focused on reactions involving both and electrons where the reactive site is not necessarily on the aromatic framework. For the nonplanar and heteropolar systems, these indices performed as well as the Hückel method did for the classical aromatics. These CNDO indices should perform effectively in multivariable regressions to parameterize the reactivities for more complicated problems such as those encountered in quantitative structure activity relationships of drugs.     

Potential applicability of MALDI-MS for low-molecular-weight pesticide determination

The application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for pesticide analysis was demonstrated. Fifteen pesticides were chosen as the model pesticides and twenty-six MALDI matrices were screened for the most suitable matrix. Under the optimized conditions, the obtained limits of detections were lower than the maximum residue limit values stated with 12 pesticides out of 15 tested. The proposed methodology showed a good analytical performance in terms of rapid, good sensitivity and high throughput of the method as an alternative method for pesticide residues evaluation.     

Contribution to the thermodynamics of emulsions

Summary In this paper there are derived equations for thermodynamically stable emulsions of phase II in phase I in the presence of surfactants.

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Zusammenfassung In dieser Arbeit werden Gleichungen für thermodynamisch stabile Emulsionen einer Phase II in Phase I in Gegenwart oberflächenaktiver Stoffe abgeleitet.

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Notation A interfacial area between phase I and phase II - interfacial tension between phase I and phase II - ⁰ interfacial tension without presence of a surfactant - n _i number of moles = amount of componenti - C ₃ concentration of the surfactant = component 3 in phase I in mol/cm³ With 1 figure and 2 tables     

On the applicability of Pierotti's theory for the solubility of gases in liquids

The applicability of Pierotti's theory for the solubility of gases in liquids is investigated by means of literature data for the case where one of the components is very polar. It appears that the values of the energy parameter ?₂/k of the solutes that follow from this theory depend on the chemical nature of the solvent. Several cases of complex formation between solute and solvent have been detected.     

Tuning metal hydride thermodynamics via size and composition: Li-H, Mg-H, Al-H, and Mg-Al-H nanoclusters for hydrogen storage

Nanoscale Li and intermetallic Al-Mg metal hydride clusters are investigated as a possible hydrogen storage material using the high-level quantum Monte Carlo computational method. Lower level methods such as density functional theory are qualitatively, not quantitatively accurate for the calculation of the enthalpy of absorption of H(2). At sizes around 1 nm, it is predicted that Al/Mg alloyed nanoparticles are stable relative to the pure compositions and the metal composition can be tuned in tandem with the size to tune the hydrogen absorption energy, making this a promising route to a rechargeable hydrogen storage material.     

Simple thermodynamics for unravelling sophisticated self-assembly processes

During the past 15 years, coordination chemistry has rapidly developed toward multicomponent assemblies involving several ligands and metal ions, which are connected via intra- or intermolecular processes. The fascinating structural aspect of these complexation reactions has been early recognized for the design of sophisticated (supra)molecular architectures with novel topologies and functions, while the concomitant energetic part only recently emerged as a potential tools for controlling and programming self-assemblies. In this Perspective, we focus on the modelling of the free energy changes accompanying self-assembly processes. Starting with the original protein-ligand model borrowed from biology, which describes complicated multicomponent assemblies, we present (i) its adaptation to coordination chemistry and (ii) its significance for addressing cooperativity as an extra energy cost resulting from intercomponent interactions. An additional entropic concept arising from the separation of intra- and intermolecular complexation processes is then discussed, together with its explicit consideration for modeling multicomponent complexation reactions. Finally, both aspects (i.e. cooperativity and intra-/intermolecular connections) are combined in the extended site binding model, which is able to dissect free energy changes occurring in sophisticated metal-ligand assemblies with a minimum set of microscopic parameters. Applications to experimental complexation reactions of increasing complexity are systematically discussed, and illustrate the potential and limitations of each model.     

Molecular thermodynamics for some applications in biotechnology

As biotechnology sweeps the world, it is appropriate to remember that the great virtue of thermodynamics is its broad range of applicability. As a result, there is a growing literature describing how chemical thermodynamics can be used to inform processes for old and new biochemical products for industry and medicine. A particular application of molecular thermodynamics concerns separation of aqueous proteins by selective precipitation. For this purpose, we need phase diagrams; for constructing such diagrams, we need to understand not only the qualitative nature of phase equilibria of aqueous proteins but also the quantitative intermolecular forces between proteins in solution. Some examples are given to show how aqueous protein–protein forces can be calculated or measured to yield a potential of mean force and how that potential is then used along with a statistical thermodynamic model to establish liquid–liquid and liquid–crystal equilibria. Such equilibria are useful not only for separation processes but also for understanding diseases like Alzheimer’s, cataracts and sickle-cell anemia that appear to be caused by protein agglomeration.

     

On the derivation and application of solution thermodynamics for reactive components

A formulation of the procedure for the application of chemical theory to the problem of calculating the thermodynamic properties of apparent components in a solution from those of the true species in the solution is presented. This formulation is simpler than the general unifying mathematical analysis previously available. Applications of the procedure to vapor-liquid equilibria, either for the calculation of phase compositions from a known thermodynamic model, as in flash calculations, or for correlation of experimental data with a proposed thermodynamic model, are discussed.     

Some criteria for the applicability of synthetic standards for laser spectral analysis of refractories

Summary The applicability of a series of synthetic standards for laser local analysis of refractories has been determined on the basis of 4 criteria: homogeneity, equality of the form and size of the craters formed by the laser beam, densities and plasma clouds. The validity of these criteria has been checked by comparison of the results received by electrone microprobe area scanning and by shooting the same places with a laser beam and reading the results with the help of synthetic standards.

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Kriterien zur Anwendbarkeit synthetischer Standards für die Laser-Spektralanalyse von feuerfesten Materialien

Zusammenfassung Die Anwendbarkeit von synthetischen Standards für die Laser-Lokalanalyse von feuerfesten Materialien wurde auf Grund von 4 Kriterien beurteilt: Homogenität, Gleichheit von Form und Größe der vom Laserstrahl verursachten Krater, Dichten und Plasmawolken. Die Gültigkeit dieser Kriterien wurde durch Vergleich der erhaltenen Ergebnisse mit den mit Hilfe der Elektronenmikrosonde erzielten Resultaten geprüft.

     

Molecular thermodynamics model for random copolymer solutions

Similar to the work done by Kambour et al. and ten Brinke et al., an effective interchange energy parameter ɛ^eff is introduced into the calculation of binodal curves for random copolymer systems according to the Revised Freed (R-F) model previously established by Hu et al. for homopolymer system. ɛ^eff is a function of chain composition and various pairs of energy parameters. For contrast, the Flory-Huggins (F-H) model has also been extended to study random copolymer system in the similar way. In order to check the validity of this kind of approach, the calculated results have been compared with the corresponding MC simulation data. It is shown that the results obtained by R-F model are quite consistent with MC simulation data while that by F-H model shows large deviation due to the excess mean-field approximation employed.     

Cellular model for zeolite gas adsorption thermodynamics

Zeolite structures allow one to use a cellular adsorption model of liquid type, which can be used to describe adsorption for a gas mixture in which adsorption forms differing in orientation can arise for molecules of a single kind, which may be accompanied by dissociative or multicentered adsorption, in which an adsorbate molecule occupies several adjacent centers. General adsorption-isotherm equations have been derived together with expressions for the major integral and differential thermodynamic functions (free and internal energies, entropy, and specific heat) in gas-mixture adsorption in the cellular model. The adsorption isotherms in it give a one-to-one correspondence between the gas composition and that in the adsorption layer at all temperatures and degrees of filling, so they can be used for regular-lattice adsorbents, but only outside the critical region.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 5, pp. 584–589, September–October, 1988.