Chemical Thermodynamics and Thermal Analysis最新文献

Applications and reports of unique properties displayed by layered double hydroxides (LDHs) are steadily increasing. Fundamental insight into LDH synthesis is essential to developing sustainable production processes, and this can be acquired through an improved understanding of their underlying thermochemistry. The collection of work presented introduces LDHs, describes essential terminology, and provides a review of currently available literature focused on modelling methods and measurement techniques used to describe and capture standard thermodynamic formation property data of LDHs. A table of standard thermodynamic formation property data of LDHs is also presented at the end of the review.

CH Bond dissociation energies for a unique selection of tertiary amines that are known substrates or inhibitors of monoamine oxidase have been calculated using density functional theory. These amines are unusual because they are the only tertiary amines that exhibit MAO substrate or inhibitor behavior. The unique structural feature common to these specific compounds is an sp³-hybridized CH₂ moiety, which is α-both to nitrogen and an C=C or CC. The stabilization afforded the resulting radicals by extended delocalization dramatically lowers both the CH bond strength of the substrate (R-H → R· + H·) and pK_a of the corresponding radical cation (RH^·+ → R· + H⁺). This interplay of structure and thermodynamics may provide the driving force for an electron transfer mechanism for MAO catalysis and inhibition.

Encrustation occurs in many processing fluids where high levels of dissolved solids are present, especially in processes that use heat transfer equipment. The deposition of these scales in the interior surfaces of an autoclave can cause major issues in the operation of industrial processes such as hydrometallurgy. The knowledge of the minerals' chemistry, distribution of the chemical forms of these minerals in the autoclave, and their solubility product can assist to inhibit these solid deposits. To model such systems, it is necessary to know the reactions involved and by extension their equilibrium constants. These electrolytic systems being strongly non-ideal, models of activity coefficients are necessary to deduce the concentration of each species. This review presents and compares various models for the calculation of activity coefficients and the thermodynamic equilibrium constants at temperatures above 25 °C. For model validity and comparison purposes, a case study on the speciation of the aqueous binary systems of H₂SO₄-Al₂(SO₄)₃ and H₂SO₄₋MgSO₄ is presented and compared with experimental data. From the results obtained and in the framework presented above, the Density equilibrium constant model coupled with the Truesdell-Jones activity coefficient model gave the best fit with experimental data at the studied temperatures of 235, 250, 270, and 300 °C.

In the current study, liquid-liquid equilibrium data of aqueous two-phase systems (ATPS) containing polyethylene glycol at the different molecular weights (1000, 2000, 6000, and 8000) - sodium L-tartrate dihydrate - water at 298.15 K were obtained. Binodal curves of mentioned systems have been determined and the effect of the molecular weight of polymer on binodal curves, tie-lines, and two-phase region sizes was studied. The results showed that increasing the molecular weight of the polymer enhances the biphasic area of the system. Also, an extended UNIQUAC equation and an extended form of Virial expansion models as new models of activity coefficient were examined to predict the phase equilibria of mentioned systems. The fitted binary interaction parameters of the model were reported. Both investigated models were capable to correlate the VLE and LLE data of the pertinent binary and ternary systems successfully. It could be observed that the extended Virial model leads to a better presentation of the data in comparison to the extended UNIQUAC model.

It is becoming eminent in the oil refining industry to diminish the sulfur content in their fuels to limit the harmful emissions of sulfur oxides (SO_x) to public health and the environment. Liquid–liquid extractions of thiophene from paraffin compounds have been investigated using 1-ethyl-3-methylimidazolium dicyanamide [emim][DCA], 1‑butyl‑3-methylimidazolium dicyanamide [bmim][DCA], and 1-benzyl-3-methylimidazolium dicyanamide [bzmim][DCA] ionic liquids at 313.15 K and an atmospheric pressure of 101.3 kPa. Liquid–liquid equilibrium data for the three ternary systems: {iso-octane (1) + thiophene (2) + [emim][DCA] or [bmim][DCA] (3)} and {tetradecane (1) + thiophene (2) + [bzmim][DCA] (3)} were determined. In addition, distribution ratios and selectivity values were computed and compared for these systems to evaluate the desulfurization competence (aptitude). The thermodynamic nonrandom two-liquid (NRTL) model was used to correlate the experimental data.

A survey of those standard inorganic materials which boil without sublimation or decomposition has yielded data for 110 unique materials. These separate according to their ambient lattice energies into groups of monohalides, dihalides, trihalides, tetrahalides and lanthanoid oxides. A wide range of boiling points occurs within each group. The lanthanoid oxides have exceptionally high boiling points which are linearly related to the atomic numbers of their lanthanoid cations through their atomic masses.

One of the most sustainable methods of energy management is thermal energy storage using renewable phase change materials. Phase change materials (PCMs) with high latent heat can store thermal energy when available and release it effectively when required. In this study, the thermal properties of a set of binary mixtures of methyl palmitate (MP) and decanoic acid (DA) have been evaluated as a new bio-based and renewable PCM. Both phase change materials are obtained from vegetable oil and are biomass-based materials. The results show that the binary eutectic mixture consisting of 30% MP and 70% DA has the desired properties as a PCM for applying as thermal energy storage in the building materials. These features include the convenient melting and freezing temperatures (T_m = 20.19 °C, T_f = 15.08 °C) and the high value of corresponding latent heats (ΔH_f =202.3 J^.g⁻¹, ΔH_m = 201.43 J^.g⁻¹). Evaluating other thermo-physical properties of this mixture also confirms its fitness for the PCM role. The composition and melting point of the eutectic point and the solid-liquid phase equilibrium for these mixtures were predicted by several thermodynamic models from which UNIQUAC showed the lowest Average Relative Deviation percentage (ARD%) of 0.29%.

The nanoparticles (Nps) of tin disulfide (SnS₂) are synthesized by sonochemical route. The Nps are characterized by dispersive analysis of X-ray energy (EDAX) and X-ray photoelectron spectroscopy (XPS) to get the chemical composition. The diffraction of X-ray (XRD) is used for determination of phase and crystal structure. The as-synthesized Nps are polycrystalline and possess hexagonal structure. The surface morphology of the as-synthesized Nps is examined by electron microscopy in scanning (SEM) and high-resolution transmission modes. The residual sample after the thermal analysis is characterized by EDAX, XPS, XRD, SEM and Fourier transformed infra-red spectroscopy. The obtained results of the post-thermal analyzed and as-synthesized SnS₂ Nps samples are compared. The thermal analysis of the Nps is carried out by recording the thermogravimetric and differential thermogravimetric curves. These simultaneous thermo-curves are recorded in the temperature range of ambient to 850 K in inert nitrogen atmosphere for three heating rates of 5, 10, 15 and 20 K·min⁻¹. The thermal curves data are analyzed by the isoconversional Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Friedman methods, and the thermodynamic parameters; activation energy (E_a), change in activation entropy (ΔS*), change in activation enthalpy (ΔH*) and change in activation Gibb's free energy (ΔG*) are determined. All the obtained outcomes are discussed in detail.

The study of plastic waste thermal decomposition and kinetics is a crucial step for optimal reactor design and the scale-up of pyrolysis technologies for chemical recycling. Kinetic parameters of individual and mixed plastic waste samples that resemble the main components of plastic waste streams (polyolefins and polyesters) were determined in this study using thermogravimetric analysis. Strong dependencies of activation energy on conversion were found for the mixtures, indicating that the process occurs in multiple steps and there are strong interactions between plastic components, lowering their activation energy during the decomposition. PP and LDPE decomposed via two separate steps whereas others decomposed via a single step process. For plastic mixtures, three dominant partially overlapping steps were identified. Kinetic deconvolution analysis improved model accuracy of mixtures and enabled the study of kinetic contributions and behaviour of individual steps. The models were then applied to predict experimental data at various heating conditions and plastic compositions.

Glass transition temperature (T_g) being a crucial thermal property, linear models for predicting T_g of deep eutectic solvents (DES) are proposed. The group contribution method and genetic algorithm using an experimental dataset of 51 DESs are applied to obtain the group contribution values for each functional group present in DESs by considering their stereochemistry. By segregating the DESs into subclasses according to their molecular structures, linear regressions for each class are performed to develop the model. The framework is used to compute the T_g of all DESs taken in this study, and it shows an absolute average deviation of 2.7%.