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- Author or Editor: V. A. Logvinenko x
- Chemistry and Chemical Engineering x
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The informative capacity of thermal analysis in the evaluation of the thermal stability of coordination compounds involving the evolution of volatile ligands is discussed. The temperature of decomposition under quasi-equilibrium conditions (Q-derivatograph, quasi-isobaric, quasi-isothermal operation) is suitable for characterizing the thermodynamic stability of compounds. The initial temperature of decomposition at linear heating indicates the reaching of a defined value of the rate constant (depending on the sensitivity of the sensing device of the instrument and on experimental conditions). The temperature sequence of increasing thermal stability may not coincide with the sequence of increasing activation energy values, since in the majority of cases it demands on the value of activation enthropy.
Abstract
The present paper deals with thermal decomposition of some spatially hindered phenols, which are in the industry as stabilizers in synthetic materials used. The investigated stabilizers are separated to two groups in respect to mechanism of decomposition (group I and II). This assumption was confirmed by chromatomass-spectrometric investigations. It allows a stabilizer for forming a plastic with variety properties to choose.
Calculation of the kinetic parameters
Thermal decomposition of some phenol stabilizers on the basis of thermoanalytical data
The paper reports the calculation of kinetic parameters (activation energy, pre-exponent and reaction order) of thermodegradation of some phenol stabilizers. For this purpose, a software package for IBM-compatible personal computers is proposed. The first calculation of kinetic parameters (E, Z, n) was carried out for these compounds. The package can be applied for kinetic calculations on the thermodegradation of other substances.
Abstract
Two bismuth salts, Bi6O4(OH)4(C17H35COO)6 and Bi6O4(OH)4(C17H35COO)6 nC17H35COOH, were synthesized. The thermogravimetry under quasi-isothermal conditions denotes the multi-step character of decomposition processes for both compounds. The thermogravimetry under linear heating was used for kinetic studies. Thermogravimetric data (obtained at different rates of linear heating) were processed with 'Netzsch Thermokinetics' computer program. Kinetic parameters were calculated only for the first decomposition step for both salts, the process is described by different nucleation equations (with and without autocatalysis).
The relationship between properties of fluorinated graphite intercalates and matrix composition
Part 5. Intercalates with acetone
Abstract
Inclusion compounds (intercalates) of fluorinated graphite matrix with acetone (C2F x Br z ·y(CH3)2CO, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to acetone. The kinetics of the thermal decomposition (the first stage of filling → the second stage of filling) was studied under isothermal conditions at 292–313 K. The relationship of the host matrices structure with inclusion compounds thermal properties and kinetic parameters is discussed.
Abstract
Volatile palladium(II) β-iminoketonates of the general formula Pd(R–C(NH)–CH–CO–R1),where R and R1 are CH3, CF3, C(CH3)3 in various combinations, were synthesized and identified. Thermal properties of the resulting palladium(II) complexes in the solid phase were studied by thermogravimetric analysis under an argon atmosphere. The temperature dependence of the saturated vapor pressure was measured for the compounds by the flow method and thermodynamic characteristics of vaporization processes, enthalpy ΔH T and entropy ΔS T o, were determined. The atom-atomic potential calculation of the van der Waals energy (E cryst) of the crystal lattice was performed and the results were compared to the experimental values of the sublimation enthalpy for the complexes under study.
Thermal dissociation processes of compounds with the composition MoO2(C6H5CONHO)2.nA (A-polar organic solvent: alcohols, aldehydes, ketones, organic acids) were investigated. Kinetics of dissociation was studied in a flow reactor, the values of activation energy and preexponential factor were calculated. The influence of a solvent nature, of the length of included molecules and of the type of crystalline lattice was studied. The sequence of kinetic stability was obtained. It corresponds to the sequence of solvent activity with respect to H-binding up with the complex. For the series of alcohols nonmonotonous dependence of kinetic parameters on the length of chain (with the division into two groups: with even and oddn) was obtained. For all the compounds studied a compensation relationship is observed (lgA=aE+b).
Porous metal–organic frameworks (MOFs) as matrices for inclusion compounds
Kinetic stability under heating
Abstract
Inclusion compounds based on metal–organic frameworks (MOFs) have promising practical application in gas storage, separation and fine purification of substances, as well as in catalysis. MOFs are crystalline compounds consisting of metal ions coordinated by bridging organic ligands that form porous structures. The kinetics of the thermal decomposition of the frameworks themselves, namely [Co2(camph)2bpy] and [Co2(asp)2bpy], was investigated (camph and asp are the anions of camphoric and aspartic acids, bpy is the organic amine, 4,4′-bipyridyl). The empty coordination polymer framework based on metal camphorates was thermally (kinetically) less stable than the polymer framework based on metal aspartate. A high kinetic stability of frameworks with aspartic complexes during heating was due to the entropic factor rather than the enthalpic one.
Thermal dissociation processes ofβ-diketonate adducts with the composition ML2 · 2B (L = acetylacetone and its substituted derivatives;M = Ni, Co;B = H2O, BuNH2CH3OH, Py, NH3) were investigated. Kinetics of dissociation were studied in a flow reactor. For dehydration processes a compensation relationship is observed (lgA=E+b), demonstrating analogous mechanisms.
