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1.
Marta Worzakowska 《Journal of Thermal Analysis and Calorimetry》2010,100(2):599-605
In pseudo bi-component separated-stage model (PBSM), the effect of the TG value at separation points on the kinetic parameters is studied by residual and theoretical analysis. Simultaneously, a new method to determine the point that is the end of 1st reaction or the initial of 2nd reaction is developed. The investigations have improved the calculation procedure of PBSM. We performed thermogravimetry (TG) analysis on oil tea wood with two-step consecutive model and parallel model. Comparison between the results of the two models and improved PBSM shows well agreements. The influence of different separation points on kinetic parameters is presented. 相似文献
2.
Anne G. D. Santos Vinícius P. S. Caldeira Mirna F. Farias Antonio S. Araújo Luiz D. Souza Allan K. Barros 《Journal of Thermal Analysis and Calorimetry》2011,106(3):747-751
In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and
its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis.
The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the
ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The
yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids
into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min−1. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition
of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods
such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (E
a), obtained by applying these method were correlated. 相似文献
3.
Adriana Fuliaş Titus Vlase Gabriela Vlase Nicolae Doca 《Journal of Thermal Analysis and Calorimetry》2010,99(3):987-992
The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate,
starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min−1. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min−1. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears.
These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic
analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates:
5, 7, 10 and 12 °C min−1. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a
nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion
dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very
near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C). 相似文献
4.
K. Chennakesavulu M. Raviathul Basariya G. Bhaskar Raju S. Prabhakar 《Journal of Thermal Analysis and Calorimetry》2011,103(3):853-862
Thermal decomposition kinetics of calix[6]arene (C6) and calix[8]arene (C8) were studied by Thermogravimetry analysis (TG)
and Differential thermal analysis (DTA). TG was done under static air atmosphere with dynamic heating rates of 1.0, 2.5, 5.0,
and 10.0 K min−1. Model-free methods such as Friedman and Ozawa–Flynn–Wall were used to evaluate the kinetic parameters such as activation
energy (E
a) and pre-exponential factors (ln A). Model-fitting method such as linear regression was used for the evaluation of optimum kinetic triplets. The kinetic parameters
obtained are comparable with both the model-free and model-fitting methods. Within the tested models, the thermal decomposition
of C6 and C8 are best described by a three dimensional Jander’s type diffusion. The antioxidant efficiency of C6 and C8 was
tested for the decomposition of polypropylene (PP). 相似文献
5.
Tiit Kaljuvee Merli Keelmann Andres Trikkel Rein Kuusik 《Journal of Thermal Analysis and Calorimetry》2011,105(2):395-403
The thermooxidative decomposition of four oil shale samples from Estonia, Jordan, Israel and Morocco and one sample of Estonian
oil shale derivative, semicoke, was studied with the aim to determine the characteristics of the process and the differences
of it related to the origin of oil shale. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380
FTIR Spectrometer were carried out under non-isothermal conditions up to 1000 °C at the heating rates of 1, 2, 5, 10 and 20 °C min−1 in an oxidizing atmosphere. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman
was used to calculate the kinetic parameters. The results of TG–DTA–FTIR analyses and the variation of activation energy E along the reaction progress α indicated the complex character of thermooxidative decomposition of oil shale and semicoke,
being at that the most complicated for Estonian and Jordanian oil shale characterized by higher content of organic matter
as compared to the other samples studied. 相似文献
6.
T. Kaljuvee I. Rudjak E. Edro A. Trikkel 《Journal of Thermal Analysis and Calorimetry》2009,97(1):215-221
The effect of heating rate on the thermal behavior of ammonium nitrate (AN) and on the kinetic parameters of decomposition
of AN and its blends with limestone and dolomite was studied on the basis of commercial fertilizer-grade AN and several Estonian
limestone and dolomite samples. Experiments were carried out under dynamic heating conditions up to 900 °C at heating rates
of 2, 5, 10 and 20 °C min−1 in a stream of dry air using Setaram Labsys 2000 equipment. For calculation of kinetic parameters, the TG data were processed
by differential isoconversional method of Friedman. The variation of the value of activation energy E along the reaction progress α showed a complex character of decomposition of AN—interaction of AN with limestone and dolomite
additives with the formation of nitrates as well as decomposition of these nitrates at higher temperatures. 相似文献
7.
Longshan Zhao Qing Li Yan Cui Jie Wang Shanshan Xu Xiaohui Chen Kaishun Bi 《Journal of Thermal Analysis and Calorimetry》2012,108(1):269-273
The thermal decomposition of a new antibiotic agent, cefuroxime lysine, was investigated by thermogravimetry analysis/derivative
thermogravimetry and differential scanning calorimetry (DSC) methods in anoxic and oxidative environments. The influence of
heating rates (including 5, 10, 15, and 20 °C/min) on the thermal behavior of cefuroxime lysine was revealed. By the methods
of Kissinger and Flynn–Wall–Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the
exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves. 相似文献
8.
K. Muraleedharan M. P. Kannan T. Ganga Devi 《Journal of Thermal Analysis and Calorimetry》2011,103(3):943-955
The thermal decomposition of potassium iodate (KIO3) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential
thermal analysis (DTA) of the thermal decomposition of KIO3 was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO3 was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental
mass loss data are in good agreement for the thermal decomposition of KIO3. The non-isothermal decomposition of KIO3 was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal
decomposition of KIO3 was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the
activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal
decomposition kinetics of KIO3 can be best described by the contracting cube equation. 相似文献
9.
The thermal decomposition kinetics of nickel ferrite (NiFe2O4) precursor prepared using egg white solution route in dynamical air atmosphere was studied by means of TG with different
heating rates. The activation energy (E
α) values of one reaction process were estimated using the methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS),
which were found to be consistent. The dependent activation energies on extent of conversions of the decomposition reaction
indicate “multi-step” processes. XRD, SEM and FTIR showed that the synthesized NiFe2O4 precursor after calcination at 773 K has a pure spinel phase, having particle sizes of ~54 ± 29 nm. 相似文献
10.
Pyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by
thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C
for four heating rates: 2 K min−1, 5 K min−1, 10 K min−1, and 15 K min−1. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were
evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The
decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin
decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters
such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive
stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order
does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic
parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the
simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it
is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds. 相似文献
11.
《Journal of Analytical and Applied Pyrolysis》2006,75(1-2):231-237
Kinetics of neoprene thermal decomposition has been performed under dynamic conditions at different heating rates, between 5 and 80 °C/min in a TG apparatus. The same kinetic model has been applied simultaneously to runs performed at different heating rates and different atmospheres allowing a good correlation of the weight loss data. A mechanism based on three independent reactions has been used to model the thermal decomposition. The first reaction is of an order close to two, and the other two reactions are of order below one, similar to other plastic materials. Different alternatives for the mathematical treatment for fitting TG data were considered. The accuracy of the calculated kinetic parameters was studied by means of a sensibility analysis. 相似文献
12.
Gerlania S. Silva A. G. Souza J. R. Botelho M. C. D. Silva T. M. S. Silva 《Journal of Thermal Analysis and Calorimetry》2007,87(3):871-874
Cis-norbixin
isomer obtained by hydrolysis of cis-bixin and isolated by solvent extraction
from annatto seeds. The thermal decomposition data of the cis-norbixin samples
were analyzed by thermogravimetric analysis at different heating rates in
the 25–900°C temperature range. DSC curves showed that thermal decomposition
reactions for cis-norbixin occurred in the solid phase. The kinetic parameters,
such as activation energy and pre-exponential factor were determined using
integral and approximate methods: Coats–Redfern, Madhusudanan, Horowitz–Metzger
and Van Krevelen. F1 mechanism describes well the first stage of the thermal
decomposition. 相似文献
13.
S. Xiu H. K. Rojanala A. Shahbazi E. H. Fini L. Wang 《Journal of Thermal Analysis and Calorimetry》2012,107(2):823-829
Pyrolysis and combustion characteristics of bio-oil derived from swine manure were investigated using thermogravimetry techniques.
Thermogravimetric analysis of the bio-oils were carried out in O2 and N2 atmosphere under different heating rates (5–20 °C/min) to a maximum temperature of 900 °C. The results indicate that the
combustion processes of bio-oil occurred in three stages, namely the water and the lighter compound evaporation, i.e., the
release of the volatile compounds, ignition and burning of the heavier compounds (mainly carbon), and finally decomposition
of the carbonate compounds. The effect of heating rate was also studied, and higher heating rates were found to facilitate
the combustion process. Different reaction kinetic mechanisms were used to treat TG data, and showed that diffusion models
are the best fit for describing the combustion of bio-oil in air. The kinetic parameters of the three stages were determined
using Coats–Redfern method. The study provided reliable basic data for the burning of bio-oil. 相似文献
14.
A. Aboulkas K. El Harfi A. El Bouadili M. Nadifiyine 《Journal of Thermal Analysis and Calorimetry》2010,100(1):323-330
Investigations into the pyrolytic behaviours of oil shale, poly (ethylene terephthalate) (PET) and their mixture have been
conducted using a thermogravimetric analyzer. Experiments were carried out dynamically by increasing the temperature from
298 to 1,273 K with heating rates of 2–100 K/min under a nitrogen atmosphere. Discrepancies between the experimental and calculated
TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation
temperature of each component in the mixture was higher than those the individual components; thus an increase in thermal
stability was expected. The kinetic processing of thermogravimetric data was carried out using Flynn–Wall–Ozawa (FWO) method. 相似文献
15.
T. Vlase Gabriela Vlase Dorina Modra N. Doca 《Journal of Thermal Analysis and Calorimetry》2007,88(2):389-393
Thermal behavior of four food
dyes, i.e. tartrazine, crysoine, azorubine and amarant was studied under non-isothermal
conditions, in dynamic air atmosphere and at heating rates of 5, 10, 15 and
20°C min–1. The TG data were correlated
to the FTIR spectra of each sample, before and after the thermal decomposition.
Kinetic study by processing the TG data was performed. The main conclusion
of this study is that the non-parametric kinetic method allows a separation
of the steps of a complex process and that the values of the activation energy
obtained by this method agree satisfactory with that of Flynn–Wall–Ozawa
estimation. 相似文献
16.
In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. The degradation is
investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to
20°C min−1 . Curves obtained by TG in air are quite different from those obtained in nitrogen. A three-step loss is observed during
dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. To elucidate this difference,
a kinetic analysis is carried on. A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic
parameters of the composite decomposition. Apparent activation energy calculated by Kissinger method in oxidative atmosphere
for each step is between 40–50 kJ mol−1 upper than E
a calculated in inert atmosphere.
The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (E
a ≈130 kJ mol−1 ) even though the thermal degradation in nitrogen flow presents a maximum E
a for 15% mass loss (E
a ≈60 kJ mol−1 ).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
18.
Aouad A. Bilali L. Benchanâa M. Mokhlisse A. 《Journal of Thermal Analysis and Calorimetry》2002,67(3):733-743
The natural phosphate and its demineralization products from Moroccan deposit were pyrolysed in a thermogravimetric analyser
(TG) to examine the influence of the heating rate and mineral matter on their thermal decomposition. The heating rates investigated
in the TG were 5–100°C min−1 to final temperature of 1200°C. The integral method was used in the analysis of the TG to determine the kinetic parameters.
It has been found that for the natural phosphate and corresponding kerogen analysed in the TG, the increase of the heating
rate shifts the maximum rate loss to higher temperature. A first order reaction was found to be adequate for pyrolysis in
the range 150–600°C which was attributed to kerogen decomposition. In addition, the results indicate that the removal of mineral
matter affected the kinetic parameters found for kerogen in the natural phosphate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Banjong Boonchom Samart Kongtaweelert 《Journal of Thermal Analysis and Calorimetry》2010,99(2):531-538
The kinetics and thermodynamics of the thermal dehydration of aluminum phosphate monohydrate, AlPO4 · H2O were studied using thermogravimetry (TG-DTG-DTA) at four heating rates in dry air atmosphere. The activation energies of
the dehydration step of AlPO4 · H2O were calculated through the methods of Friedman (FR) and Flynn–Wall–Ozawa (FWO) and the possible conversion function has
been estimated through the Achar and Li–Tang equations. The independent activation energies on extent of conversions and the
better kinetic model of the dehydration reaction for AlPO4 · H2O indicate single kinetic mechanism and the F
2.05
model as a simple n-order reaction of “chemical process or mechanism no-invoking equation”, respectively. The positive values
of ΔH# and ΔG# for the dehydration reaction show that it is endothermic and non-spontaneous process and it is connected with the introduction
of heat. The kinetic and thermodynamic functions calculated for the dehydration reaction by different techniques and methods
were found to be consistent. 相似文献
20.
T. Vlase Gabriela Vlase N. Doca G. Ilia Adriana Fulias 《Journal of Thermal Analysis and Calorimetry》2009,97(2):467-472
The thermal behavior of Cd2+ and Co2+ vinyl-phosphonates was studied using two different experimental strategies: the coupled TG–EGA (FTIR) technique by decomposition
in nitrogen, respectively, air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates.
The both compounds exhibited a good thermal stability: in nitrogen, only an endothermic dehydration step was observed. In
air the Cd2+ salt presents the same dehydration step whereas by the Co2+ salt two simultaneous processes take place dehydration, respectively, thermooxidative destruction of the vinyl group. The
kinetic analysis of the TG data was performed with the Flynn–Wall–Ozawa, Friedman’s, and modified non-parametric kinetic methods.
By means of the coupled techniques, some spectroscopic arguments on the reaction mechanism were obtained. The values of the
activation energy by the three methods are in good agreement and support the two different suggested mechanism. 相似文献