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1.
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the
basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried
out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material
was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied
using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the
heating rate of 10 °C min −1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min −1 in a stream of dry air. 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 the value of activation
energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions
occurring at thermal treatment of AN prills coated with limestone and dolomite powder. 相似文献
2.
Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious
disadvantages — being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage
of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing
substances — mainly Estonian limestone and dolomite — as internal additives on thermal behaviour of AN.
Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated
on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C
(10°C min −1) in a stream of dry air or N 2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR).
The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the
decomposition of AN in air or in N 2. At the thermal treatment of AN’s blends with CaCO 3, MgCO 3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism — depending on
the origin and the content of additives, partially or completely, through the formation of Mg(NO 3) 2 and Ca(NO 3) 2. 相似文献
3.
Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In
this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning
calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG
analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300
and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it
decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the
heating rate (5, 10, 15, and 20 °C min −1) on the DSC behavior of the both drug samples was verified. The results showed that, as the heating rate was increased, decomposition
temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor
for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the
values of activation energy obtained by various methods, the following order for the thermal stability was noticed: naproxen
> celecoxib. Finally, the values of Δ S
#, Δ H
#, and Δ G
# of their decomposition reaction were calculated. 相似文献
4.
Urea is one of the main nitrogen fertilizers used in agriculture. But being well soluble in water, hardly 50% of its nitrogen is assimilated by plants. One possibility to eliminate this disadvantage is to use coating agents for modification of urea to obtain a controlled-realized fertilizer. The aim of this research was to study the influence of different lime-containing additives on the thermal behavior and decomposition kinetics of urea in oxidizing atmosphere. Commercial fertilizer-grade urea (46.4% N) and analytical-grade CaO, MgO, CaCO 3, MgCO 3 were used in the experiments. In addition, one Estonian limestone and one dolomite sample were used as additive or coating material. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer by a heated transfer line were carried out under non-isothermal conditions up to 900 °C at the heating rate of 5 °C min ?1 and to calculate kinetic parameters, additionally, at 1, 2, and 10 °C min ?1 in the atmosphere containing 80% of Ar and 20% of O 2. The differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results obtained indicate that thermooxidative decomposition of urea as well as the blends of urea with lime-containing materials and urea prills coated with limestone or dolomite powder follows a complex reaction mechanism. 相似文献
5.
Meglumine, (2 R,3 R,4 R,5 S)-6-methylaminohexane-1,2,3,4,5-pentol, is a carbohydrate derived from sorbitol in which the hydroxyl group in position one
is replaced by a methylamine group. It forms binary adducts with substances having carboxyl groups, which have in common the
presence of hydrogen bonding as the main force in the stabilization of these species. During melting, adducts of meglumine
with flunixin (2-[[2-methyl-3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid) polymerize or self-assemble in amorphous
supramolecular structures with molecular weights around 2.0 × 10 5 kDa. DSC curves, in a first heating, show isomorphic transitions where the last one at 137 °C for the flunixin-meglumine
adduct originated the supramolecular amorphous polymers with glass transition around 49.5 °C. The kinetic parameters for the
thermal decomposition step of the polymers were determined by the Capela-Ribeiro non-linear isoconversional method. From data
for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15, and 20 °C min −1, the E
α and B
α terms could be determined and, consequently, the pre-exponential factor, A α, as well as the kinetic model, g(α). 相似文献
6.
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
7.
The pyrolysis characteristics and kinetics of sewage sludge for different sizes ( d < 0.25 mm, 0.25 mm < d < 0.83 mm, and d > 0.83 mm) and heating rates (5, 20, and 35 °C/min) were investigated in this article. The STA 409 was utilized for the sewage
sludge thermogravimetric analysis. FTIR analysis was employed to study the functional groups and intermediates during the
process of pyrolysis. Meanwhile, a new method was developed to calculate pyrolysis kinetic parameters (activated energy E, the frequency factor A, and reaction order n) with surface fitting tool in software MATLAB. The results show that all the TG curves are divided into three stages: evaporation
temperature range (180–220 °C), main decomposition temperature range (220–650 °C), and final decomposition temperature range
(650–780 °C). The sewage sludge of d < 0.25 mm obtains the largest total mass loss, especially at the heating rate of 5 °C/min. By FTIR analysis, the functional
groups including NH, C–H, C=C, etc., are all found in the sewage sludge. There is a comparison between the FTIR spectra of
sludge heated to 350 °C (temperature associated to maximum devolatilization rate in the second stage) and the FTIR spectra
of sludge heated to 730 °C (temperature associated to maximum devolatilization rate in the third stage). In the second stage,
the alcohols, ammonia, and carboxylic acid in the sludge have been mostly decomposed into gases, and only a little bit of
compounds containing CH and OH of COOH exist. The pyrolysis kinetic parameters of second stage are as follows: the reaction
orders are in the range of 1.6–1.8 and the activation energy is about 45 kJ/mol. The frequency factor increases with the increase
of heating rate and sewage sludge size. 相似文献
8.
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
9.
The thermal stability of HMT under dynamic, isothermal and adiabatic conditions was investigated using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. It is found from the dynamic DSC results that the exothermic decomposition reaction appears immediately after endothermic peak, a coupling phenomenon of heat absorption and generation, and the endothermic peak and exothermic peak were indentified at about 277–289 and 279–296 °C (Tpeak) with the heating rates 1, 2, 4 and 8 °C min−1. The ARC results reveal that the initial decomposition temperature of HMT is about 236.55 °C, and the total gas production in decomposition process is 6.9 mol kg−1. Based on the isothermal DSC and ARC data, some kinetic parameters have been determined using thermal safety software. The simulation results show that the exothermic decomposition process of HMT can be expressed by an autocatalytic reaction mechanism. There is also a good agreement between the kinetic model and kinetic parameters simulated based on the isothermal DSC and ARC data. Thermal hazards of HMT can be evaluated by carrying out thermal explosion simulations, which were based on kinetic models (Isothermal DSC and ARC) to predict several thermal hazard indicators, such as TD24, TD8, TCL, SADT, ET and CT so that we can optimize the conditions of transportation and storage for chemical, also minimizing industrial disasters. 相似文献
10.
The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM)
which was used to prepare nano-MnFe 2O 4 particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of
2.5, 5 and 7.5°C min −1respectively under the atmosphere of dynamic air from room temperature to 400°C.
The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the
temperature up to 60°C. The maximum speed of decomposition (dα/d T) m at the heating rate of 5 and 7.5°C min −1 was more than 10 times of that at 2.5°C min −1 and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty
of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion
degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be
described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction. 相似文献
11.
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
12.
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
13.
The paper presents a non-isothermal kinetic study of the decomposition of Zn acetate-based gel precursors for ZnO thin films,
based on the thermogravimetric (TG) data. The evaluation of the dependence of the activation energy ( E) on the mass loss (Δ m) using the isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) has been presented
in a previous paper. It was obtained that the sample dried at 125°C for 8 h exhibits the activation energy independent on
the heating rate for the second decomposition step. In this paper the invariant kinetic parameter (IKP) method is used for
evaluating the invariant activation parameters, which were used for numerically evaluation of the function of conversion.
The value of the invariant activation energy is in a good agreement with those determined by isoconversional methods. In order
to determine the kinetic model, IKP method was associated with the criterion of coincidence of the kinetic parameters for
all heating rates. Finally, the following kinetic triplet was obtained: E=91.7 (±0.1) kJ mol −1, ln A(s −1)=16.174 (±0.020) and F1 kinetic model. 相似文献
14.
Thermal pyrolysis of pharmaceutical wastewater sludge, brown coal, and sludge-coal blends were studied by TG dynamic runs
carried out at 20 °C min −1 in the temperature range from 25 to 850 °C. Different possible kinetic models of thermal decomposition have been considered.
The best models of mechanism function for brown coal, pharmaceutical wastewater sludge, and coal–sludge blends are a first-order
reaction, a N-dimensional nucleation, and growth reactions with N = 2 and 4, respectively. The Arrhenius kinetic parameters for brown coal, pharmaceutical wastewater sludge, and coal–sludge
blends are proposed. 相似文献
15.
The authors present their results concerning the decomposition in air of the homopolynuclear coordination compound [CoC 2O 4·2.5H 2O]
n
. In the temperature range 20–300 °C, the heating curves TG, DTG and DTA allowed to evidence three decomposition steps. The
kinetic analysis was performed on the second step which proved to be the only workable one. The application of nonlinear regression
procedure shows that this is a complex process consisting in three successive steps. The checking of the mechanism and corresponding
kinetic parameters for quasi-isothermal data ( T = 150 °C) shows that the obtained results could be used for prediction of the thermal behaviour of the investigated compound
in both isothermal and non-isothermal conditions. 相似文献
16.
Thermal behavior of Co(II), Cd(II), and Zn(II) complexes with N-benzyloxycarbonylglycinato ligand was investigated using the results of TG, DSC and DTG analysis obtained at different heating
rates (2.5 to 30 °C min −1), from room temperature to about 900 °C. Mechanisms of complex degradation, as well as enthalpies of the degradation processes
were determined. It is shown that thermal stability of investigated complexes correlates with their crystal structures, especially
with the presence of crystallization and coordinated water molecules. The values of dehydration enthalpies are discussed and
correlated with composition of the complexes. Kissinger’s, Ozawa’s, and Friedman’s isoconversion methods were used for the
determination of kinetic parameters: the pre-exponential factor A and the apparent activation energy E
a. For all three complexes and all steps of degradation, the values of kinetics parameters obtained by Kissinger’s and Ozawa’s
methods are in good agreement. The results obtained by Friedman’s method showed that some decomposition steps are simple and
some others are complex ones. 相似文献
17.
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
18.
In this work, the bioenergy potential of green microalgae Scenedesmus acuminatus was evaluated through the psychochemical characteristics and kinetic study of pyrolysis, where the results indicate a good candidate for application in the thermochemical process due to its low moisture and ash content and high calorific value. Its thermal behavior under a heating rate of 10 °C min?1 and inert atmosphere shows that decomposition occurs in two stages. Stage I (125–309 °C) involves the pyrolysis of carbohydrates and protein and stage II (309–501 °C) the pyrolysis of lipids. The Starink isoconversional method showed a better application for simulation curves, compared with methods of FWO and KAS. The average values of activated energy were 107.1 and 132.6 kJ mol?1 for stages I and II, respectively, which indicates that pyrolysis occurs more easily in stage I than in stage II. The conversion rate curves show that the calculated kinetic parameters are satisfactory for the evaluation of the thermochemical systems. 相似文献
19.
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
20.
In this paper, the thermal behaviours of two organophosphorous compounds, N, N-dimethyl- N′, N′-diphenylphosphorodihydrazidic (NDD) and diphenyl amidophosphate (DPA), were studied by thermogravimetery (TG), differential
thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques under non-isothermal conditions. The results
showed that NDD melts about 185 °C before it decomposes. NDD decomposition occurs in two continuous steps, in the 190–410 °C
temperature range. First thermal degradation stage for NDD results a broad exothermic peak in the DTA curve that is continued
with a small exothermic peak at the end of decomposition process. On the other hand, applying TG-DTA techniques indicates
that DPA melts about 150 °C before it decomposes. This compound decomposes in the temperature range of 230 to 330 °C in two
steps. These steps are endothermic and exothermic, respectively. Activation energy and pre-exponential factor for the first
step of decomposition of each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method.
Activation energy obtained by Kissinger method for the first stage of NDD and DPA decompositions are 138 and 170 KJ mol −1, respectively. Finally, the thermodynamic parameters (Δ G
#, Δ H
# and Δ S
#) for first step decomposition of investigated organophosphorous were determined. 相似文献
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