Thermogravimetric techniques have been used to study the kinetics of thermal deamination of tris(ethylenediamine)nickel(II)
sulphate. The complex was synthesized and characterized by various chemical and spectral techniques. Thermal decomposition
studies were carried at different heating rates (5, 10, 15 and 20°C min−1) in dynamic air. The complex undergoes a four-stage decomposition pattern. The stages are not well resolved. Decomposition
path can be interpreted as a two-stage deamination, and a two-stage decomposition. Reaction products at each stage were separated
and identified by means of IR and XRD. The morphology of the complex and the residue were studied by means of SEM. Final residue
of the decomposition was found to be crystalline NiO.
The deamination kinetics was studied using model-free isoconversional methods viz., Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose
(KAS) methods. It is observed that the activation energy varies with the extent of conversion; indicating the complex nature
of the deamination reaction.
The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is
shown that the application of this method should be preceded by the application of an isoconversional method through which
the dependence of the activation energy, E, on the conversion degree,a,
should be established. If Edepends ona, Diefallah's composite integral
method leads to erroneous results. If Edoes not depend ona, the
true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two
sets of non-isothermal data, namely: (a) the TG curves corresponding to the dehydration of CaC2O4H2O; (b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride (PVC).
There is an increasing concern with the environmental problems associated with the increasing CO2, NOx and SOx emissions resulting from the rising use of fossil fuels. Renewable energy, mainly biomass, can contribute to reduce the fossil
fuels consumption. Biomass is a renewable resource with a widespread world distribution. Pistachio is available in large quantities
in Gaziantep region in Turkey. Pistachio shell has a good energy potential for exploitation through pyrolysis and gasification.
This study deals with the thermal degradation characteristics of in different particle sizes pistachio shell and its kinetics.
Thermal degradation analysis have been done by using a thermogravimetric analyzer from room temperature to 800°C in N2 atmosphere at different heating rates (5, 10, 15 and 20°C min−1). TG and DTG curves exhibited two distinct degradation zones. Kinetic parameters were calculated by using Coats-Redfern method
and model-free isoconversional Flynn-Wall-Ozawa (FWO) kinetic method.
The possibility to determine the kinetic parameters for temperature programmed reduction of Cu/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another
one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti
and Baiker, the Friedman’s method, although gives values of the activation energy smaller than the real values, indicates
a very similar dependence of these on the reduction degree. On the basis of some synthetic data one shows that the errors
are very large when these recommendations are neglected, being possible to determine a false dependence on the degree of reduction.
Authors:S. Vyazovkin, J. Stone, and N. Sbirrazzuoli
Summary By applying an advanced isoconversional method to DSC data one can evaluate a dependence of the effective activation energy (the temperature coefficient of the growth rate) on the relative extent of melt crystallization. The conversion dependence can further be converted into a temperature dependence and parameterized in terms of the Hoffman-Lauritzen equation. For poly(ethylene terephthalate) (PET) we observe a transition from regime I to II. Poly(ethylene oxide) (PEO) crystallization appears to begin in regime II and then undergoes 2 consecutive changes that however cannot be clearly interpreted as regime III. The Kg and sse parameters obtained for regime I and II (PET) and regime II (PEO) are consistent with the respective parameters reported for isothermal crystallization.
A new method of the multiple rate iso-temperature was used to define the most probable mechanism g(α) of a reaction; the iterative iso-conversional procedure has been employed to estimate apparent activation energy Ea, the pre-exponential factor A was obtained on the basis of Ea and g(α). In this new method, the thermal analysis kinetics triplet of dehydration of calcium oxalate monohydrate is determined,
which apparent activation energy Ea is 82.83 kJ mol-1, pre-exponential factor A is 1.142105-1.235105 s-1, the most probable mechanism belongs to phase boundary reaction Rn with integral form g(α)=1-(1-α)n and differential form f(α)=n(1-α)1-(1/n), where accommodation factor n=2.40-1.40.
Authors:M. Alonso, M. Oliet, J. García, F. Rodríguez, and J. Echeverría
Kinetics of thermosetting polymers curing is difficult to study by isothermal
methods based on the differential scanning calorimetry (DSC) technique. The
difficulty is due to the low sensitivity of the equipment for total reaction
heat measurements during high temperature process. The aim of this paper is
to display the equivalence between a dynamic model, the Ozawa method, and
an isothermal isoconversional fit, which allows predicting the isothermal
behavior of the resol resins cure through dynamic runs by DSC. In this work,
lignin–phenol–formaldehyde and commercial phenol–formaldehyde
resol resins were employed. In addition, the isothermal kinetic parameters
for both resins were performed by means of transformation of the data obtained
from the dynamic Ozawa method.
Thermal behavior of nitroguanidine (NQ) has been investigated by TG/DSC-MS-FTIR simultaneous analysis performed under both
isothermal and nonisothermal conditions. The isothermal test at 230 °C indicated that the release of gas products can be divided
into several stages. The processing of the non-isothermal data, namely 5, 10, 15, and 20 K/min, was performed by using Netzsch
Thermokinetics. The dependence of the activation energy evaluated by Friedman’s isoconversional method on the conversion degree
shows that the investigated process is complex one, and can be divided into three parts. The mechanism of the process and
the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program. The kinetic results was
used to simulate the thermal decomposition of NQ under isothermal condition at 210 °C. The simulated curve is in agreement
with the tested curve. The obtained results were also used for prediction of the thermal lifetime of NQ corresponding to a
The thermo-oxidative degradation of a parchment recent manufactured from a goat skin has been investigated by TG/DTG, DSC
simultaneous analysis performed in static air atmosphere, at six heating rates in the range 3–15 K min−1. At the progressive heating in air atmosphere, the investigated material exhibits three main successive processes occurring
with formation of volatile products, namely the dehydration followed by two thermo-oxidative processes. The processing of
the non-isothermal data corresponding to the first process of thermo-oxidation was performed by using Netzsch Thermokinetics—a
Software Module for Kinetic Analysis. The dependence of activation energy, evaluated by isoconversional methods suggested
by Friedman, and Ozawa, Flynn and Wall, on the conversion degree and the relative high standard deviations of this quantity
show that the investigated process is a complex one. The mechanism and the corresponding kinetic parameters were determined
by Multivariate Non-linear Regression program. Three mechanisms, one consisting in four successive steps and two others in
five successive steps, exhibit the best F-test Fit Quality for TG curves. It was also used the previously suggested criterion, according to which the most probable
process mechanism correspond to the best agreement between EFR = EFR (α) (EFR is the activation energy evaluated by isoconversional method suggested by Friedman; α is the conversion degree) obtained
from non-isothermal experimental data and activation energy values, Eiso, obtained by applying the differential method to isothermal data simulated using non-isothermal kinetic parameters. According
to this last criterion, the most probable mechanism of parchment oxidation consists in four successive steps. The contribution
of the thermo-oxidation process in the parchment damage by natural aging is discussed.
Authors:Hichem Eloussifi, Jordi Farjas, Pere Roura, and Mohamed Dammak
transformation. Isoconversional model-free methods analyze the evolution of a given parameter at a given degree of transformation, α. The main advantages of using kinetic data from the isoconversional methods is twofold: (a) there is common agreement that