The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques
in different atmospheres of N2, H2 and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds
(i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction.
IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination
at different temperatures and in different atmospheres. CoO was identified as the final solid product in N2, and Co3O4 was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used
to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous
products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid,
CO2 and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere.
Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, Cp and °S) were calculated for the different decomposition steps.
Authors:Fei-Xiong Chen, Cai-Rong Zhou, and Guo-Peng Li
and growth, and its reaction order n is 4, and
Compensation effect of non-isothermaldecomposition kinetic of glyphosate
Usually, the phenomenon of a linear relationship between ln A and E is known as kinetic
The non-isothermal decomposition of anhydrous disilver malonate was studied up to 300°C by means of TG, DTA and DSC techniques
in different atmospheres (e.g. N2, H2 and air). Acetic acid, CO2, acetone and CO were identified as the volatile decomposition products using gas chromatography. Silver metal, on the other
hand, was identified as the final solid product using X-ray powder diffraction. The mechanism described involves the breakdown
of adsorbed radicals, probably including-CH2COO- and related species, on the surface of the metallic silver product.
The activation energy (ΔE) and the frequency factor (InA) were calculated for the decomposition process from the variation of peak temperature (of the DTA curves) with the rate of
heating (φ). The enthalpy change (ΔH), the heat capacity (Cp) and entropy change (ΔS) were calculated from the DSC measurements.
Ammonium dinitramide (ADN) prills were prepared by emulsion crystallization and characterized by optical microscopic, thermogravimetric
(TG) and differential scanning calorimetric (DSC) techniques. The isothermal and non-isothermal decomposition kinetics of
ADN prills were studied by TG. The differential isoconversional method of Friedman (FR) and integral isoconversional method
of Vyazovkin were used to investigate the dependence of activation energy (Ea) with conversion (α) and the results were compared with literature data. The dependence of activation energy was also derived
from isothermal data. A strong dependence of Ea with α is observed for the ADN prills. All the methods showed an initial increase in Ea up to α=∼0.2 and later decreases over the rest of conversion. The apparent Ea values of FR method are higher than that of Vyazovkin method up to α=∼0.45. The calculated mean Ea values by FR, Vyazovkin and standard isoconversional method for α between 0.05 and 0.95 were 211.0, 203.9 and 156.9 kJ mol−1, respectively.
A “true” kinetic compensation effect was established using the most appropriate kinetic functionF(α) for the non-isothermal decomposition of solids at various heating rates. It is likely that the correct kinetic mechanismF(α) is responsible for the “true” kinetic compensation effect, whereas an inappropriateF(α) would lead to “false” one.
The non-isothermal decompositions of silver maleate dihydrate (C4H2O4Ag22H2O) and anhydrous silver fumarate (C4H2O4Ag2) were studied up to 500°C, in a dynamic atmosphere of air, by means of TG and DTA measurements. Both compounds showed some
sublimation (at 120°C for silver maleate and at 180°C for silver fumarate) prior to the onset of decomposition (at 170°C for
silver maleate and at 280°C for silver fumarate).
The gaseous decomposition products of both compounds were found, using IR spectroscopy, to be dominated by maleic anhydride
and CO2. Minor proportions of ethylene, ethyl alcohol, acetone, methane and isobutene were also identified. Metallic silver was the
final solid product, as identified by X-ray diffractometry. NMR analysis was used to monitor the isomerization of the maleate
radical into the more stable fumarate above 230°C. Kinetic parameters (Ea and lnA) were calculated from the effect of heating rate, (2, 5, 10, and 20 deg min−1) on the DTA measurements.
A mechanism is suggested for the decomposition pathways of these compounds, on basis of the results obtained and, also, on
similarities with analogous systems.
This paper reports a comparative study of the non-isothermal decompositions of the heteropolyacids HPM and HPVM, with structures
consisting of Keggin units (KUs). Non-isothermal analysis at low heating rates demonstrated the existence of 4 crystal hydrate
species, depending on the temperature. The stability domains of the anhydrous forms of HPM and HPVM were found to be 150–380°C,
respectively. Processing of the TG curves obtained at different heating rates by the Ozawa method revealed that the decomposition
of anhydrous HPM takes place according to a unitary mechanism, whilst for anhydrous HPVM two mechanisms are observed. Thus,
the first part of the constitution water is lost simultaneously with the departure of vanadium from the KU as VO2+, while the second part is lost at higher temperatures as in the case HPM.
Authors:T. Vlase, N. Doca, Gabriela Vlase, C. Bolcu, and F. Borcan
In the present work a comparative kinetic study was performed on the thermal behavior of three antioxidants of IRGANOX-type
(L101, L109 and L115) in dynamic air atmosphere under non-isothermal conditions.
The TG-DTG data were obtained at heating rates of 5, 7, 10 and 15 K min−1. The kinetic parameters were obtained by processing these data with strategies corresponding to Flynn-Wall-Ozava (FWO), Friedman
(FR), Budrugeac-Segal (BS) and non-parametric kinetic (NPK) methods.
The thermal degradation by all the three compounds take place in melted state, so that any kinetic models regarding the decomposition
of solids are inapplicable. Only with the NPK method it was possible a separation between the two functions of the reaction
For the temperature dependence, f(T), an Arrhenius-type model was searched; for the conversion dependence, the Ŝestak-Berggren equation was suggested in order
to discriminate between physical (m) and chemical (n or p) steps of a complex thermodegradation process.
Authors:G. Anbalagan, P. Rajakumar, and S. Gunasekaran
Thermal decomposition behaviour of ten Indian limestones of marine origin have been studied by thermogravimetric (TG) and
differential thermal analysis (DTA). DTA curves of limestone samples show asymmetric peak with index of shape about 0. 25.
The size of calcite characteristic endothermic DTA peak remains unaffected due to the presence of impurities such as SiO2 and Al2O3. The presence sodium and potassium carbonate salts in the limestone have a strong effect on their decomposition. From the
thermogravimetric data the activation energy, Arrhenius factor, order of reaction and entropy for activation were calculated
using three different methods. TG and DTA results indicate that both temperature of decomposition and the activation energy
for decomposition of limestone is reduced and that the rate of decomposition is enhanced relative to pure calcium carbonate.
The formation of portlandite and wollastonite are strongly exothermic and thus helps in maintaining the required retorting