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1.
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 (E
a) 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 E
a with α is observed for the ADN prills. All the methods showed an initial increase in E
a up to α=∼0.2 and later decreases over the rest of conversion. The apparent E
a values of FR method are higher than that of Vyazovkin method up to α=∼0.45. The calculated mean E
a 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. 相似文献
2.
Thermal decomposition of imipramine hydrochloride and trimipramine maleate has been investigated isothermally and nonisothermally. The kinetic parameters, namely the activation energy Ea and the Arrhenius preexponential term A, were calculated. Applying the theory of activated complex to the process of decomposition one calculated ΔS≠, ΔH≠, and ΔG≠ for the reaction. The values of Ea as well as the thermodynamic functions did not vary significantly with temperature of the reaction whereas the preexponential term showed a significant dependence on the reaction temperature. Both imipramine hydrochloride and trimipramine maleate showed two main steps of decomposition. Each step proved to be a first‐order reaction. The rate constant was calculated for each step, and the results were analyzed statistically. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 166–179, 2003 相似文献
3.
Thermal Decomposition of Some Chemical Compounds Used As Food Preservatives and Kinetic Parameters of This Process 总被引:1,自引:0,他引:1
Thermal decomposition processes of selected chemicals used as food preservatives such as sodium formate, sodium propionate,
sodium nitrates(V and III) and sodium sulphate(IV) were examined by the derivatographic method. Based on the curves obtained,
the number of decomposition stages and characteristic temperatures of these compounds have been found. Mass decrements calculated
from TG curves ranged from 28.9% for sodium formate to 77.8% for sodium nitrate(V), while sodium sulphate showed a mass increment
of 5.6%. Kinetic parameters such as activation energy (E
a ), frequency factor (A ) and reaction order (n ) were calculated from TG, DTG and T curves. Sodium formate shows the highest values of E
a and A which amount to 171.7 kJ mol–1 and 5.8⋅1014 s–1 , respectively, while the lowest ones, E
a =28.2 kJ mol–1 and A =3.65⋅102 s–1 belong to sodium nitrate(V).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Prof. Dr. Stefan Grimme 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9955-9964
The equilibrium association free enthalpies ΔGa for typical supramolecular complexes in solution are calculated by ab initio quantum chemical methods. Ten neutral and three positively charged complexes with experimental ΔGa values in the range 0 to ?21 kcal mol?1 (on average ?6 kcal mol?1) are investigated. The theoretical approach employs a (nondynamic) single‐structure model, but computes the various energy terms accurately without any special empirical adjustments. Dispersion corrected density functional theory (DFT‐D3) with extended basis sets (triple‐ζ and quadruple‐ζ quality) is used to determine structures and gas‐phase interaction energies (ΔE), the COSMO‐RS continuum solvation model (based on DFT data) provides solvation free enthalpies and the remaining ro‐vibrational enthalpic/entropic contributions are obtained from harmonic frequency calculations. Low‐lying vibrational modes are treated by a free‐rotor approximation. The accurate account of London dispersion interactions is mandatory with contributions in the range ?5 to ?60 kcal mol?1 (up to 200 % of ΔE). Inclusion of three‐body dispersion effects improves the results considerably. A semilocal (TPSS) and a hybrid density functional (PW6B95) have been tested. Although the ΔGa values result as a sum of individually large terms with opposite sign (ΔE vs. solvation and entropy change), the approach provides unprecedented accuracy for ΔGa values with errors of only 2 kcal mol?1 on average. Relative affinities for different guests inside the same host are always obtained correctly. The procedure is suggested as a predictive tool in supramolecular chemistry and can be applied routinely to semirigid systems with 300–400 atoms. The various contributions to binding and enthalpy–entropy compensations are discussed. 相似文献
5.
B. V. L’vov 《Journal of Thermal Analysis and Calorimetry》2006,84(3):581-587
The main purpose of this
paper is to prove the applicability of the mechanism of congruent dissociative
vaporization (CDV) to the solid-state decomposition kinetics through the comparison
of the fundamental theoretical relationship Ei/Ee=(a+b)/a resulted
from this mechanism with experiment. It has been shown that the ratios of Ei and Ee
parameters of the Arrhenius equation measured in the isobaric and equimolar
modes (in the presence and absence of H2O vapour) for
22 reactants with the general formula aSalt⋅bH2O or aOxide⋅bH2O are in agreement with
the values of (a+b)/a. The relative standard deviation is only 17% and
the correlation coefficient is close to 0.99. A probability of accidental
correlation for all set of the E parameters
taken from the literature is lower than 4⋅10–16
. This strongly supports the validity of the CDV mechanism. The problem of
stability of polyatomic molecules of inorganic salts in the gaseous state,
which are the primary decomposition products of crystalline hydrates, was
also discussed on the basis of recent mass spectroscopy studies. It was concluded
that any doubts in the applicability of the CDV mechanism as a general mechanism
of solid-state decomposition reactions are unsound. 相似文献
6.
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
7.
Thermochemical Properties and Non-isothermal Decomposition Reaction Kinetics of N-Guanylurea Dinitramide (GUDN) 总被引:4,自引:0,他引:4
Introduction N-Guanylurea dinitramide (GUDN) is a new ener-getic oxidizer with higher energy and lower sensitivity. Its crystal density is 1.755 g·cm-3. The detonation velocity is about 8210 m·s-1. Its specific impulse and pressure exponent are 213.1 s and 0.73, respectively. It has the potential for possible use as an energy ingredient of propellants and explosives from the point of view of the above-mentioned high performance. Its preparation,1 properties2 and hygroscopocity2 have been … 相似文献
8.
9.
Relationship between Electronic Charges at Nitrogen Atoms of Nitro Groups and Thermal Reactivity of Nitramines 总被引:1,自引:0,他引:1
Thermal reactivity of eleven nitramines has been examined by means of non-isothermal differential thermal analysis, and the
data were analyzed according to the Kissinger method. The reactivity was expressed as the E
a
R
−1 slopes of the Kissinger relationship. Electronic charges, q
N, at nitrogen atoms of the nitramine molecules were calculated by means of ab initio DFT B3LYP/6-31G** method. The relationships
were confirmed between the slopes E
a
R
−1 and the q values for the nitro groups that are primarily split off. Conclusions are made in relation to the mechanism of
initiation of polynitro compounds in general.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
11.
Catalytic activity of catalase (CAT) immobilized on a modified silicate matrix to mediate decomposition of meta-chloroperoxibenzoic
acid (3-CPBA) in acetonitrile has been investigated by means of quantitative UV-spectrophotometry. Under the selected experimental
conditions, the kinetic parameters: the apparent Michaelis constat (K
M
), the apparent maximum rate of enzymatic reaction (V
max
app
), the first order specific rate constants (k
sp
), the energy of activation (E
a
) and the pre-exponential factor of the Arrhenius equation (Z0) were calculated. Conclusions regarding the rate-limiting step of the overall catalytic process were drawn from the calculated
values of the Gibbs energy of activation ΔG*, the enthalpy of activation ΔH*, and the entropy of activation ΔS*. 相似文献
12.
Bharti U. N. Verma Kingsuk Mukhopadhyay 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1071-1075
The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine
and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)2]·2H2O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior
of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min−1 under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters
such as order of reaction (n), activation energy (E
a), frequency factor (Z) and entropy of activation (∆S
≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako
(J Phys Chem 72(7):2406–2411, 1968). 相似文献
13.
Yi-Yuan Peng Jian Huang Yan-Ling Qu Cheng-Xue Zhao 《Research on Chemical Intermediates》2000,26(6):587-597
Pentafluoroethyl t-butyl nitroxides (3) have been generated by the use of electron-transfer reactions of O-benzoyl-N-t-butylhydroxylamine (1) and pentafluoropropanoyl peroxide (2) in F113 (CFCl2CF2Cl) solution. ESR measurement of aN and aF
β values for 3 in 11 solvents have been carried out at 17 ± 2 °C. The aN values for 3 in 10 aprotic solvents (but not in i-PrOH) show a linear correlation with the cybotactic solvent parameter ET, i.e. aN = 3.02 × 10−2 ET ± 10.46. Together with the similar correlation analysis for trifluoromethyl t-butyl nitroxide (4) and heptafluoropropyl t-butyl nitroxide (5) reported previously, the physical significance for the slope, slope × ET, the extrapolated intercept on the aN axis, is linked to the sensitivity of the nitroxide toward solvation, the magnitude of the overall solution effect on the
aN values, and the intrinsic aN values of 3, 4, 5 in the ideal gaseous state, respectively. The intercepts on the aN axis, 11.34 G, 11.56 G and 11.37 G may serve a new measure of electronegativity for CF3, C2F5 and n-C3F7, respectively. The plots of aN versus noncybotactic solvent constants, such as dipolar moment (μ) and dielectric constant (ɛ), all show random cases. 相似文献
14.
Stable s-butyl trifluoroacetyl nitroxide (3) has been generated in electron-transfer reaction of O-benzoyl-N-s-butylhydroxylamine (1) and trifluoroacetyl peroxide (2) in F113 (CFCl2CF2Cl) solution at room temperature. ESR measurement of a
N and a
H
values for 3 in 21 solvents has been carried out at 24~ 25°C. The a
N values for 3 in 12 aprotic solvents show a linear correlation with the cybotactic solvent parameters E
T and Z, i.e. a
N = 1.35×10-2
E
T+6.84, a
N = 0.78×10-2
Z+6.88. The physical significance for the slopes, slope × E
T or slope × Z, the extrapolated intercepts on the a
N axis are linked to the sensitivity of the nitroxide toward the solvation, the magnitude of the overall solvaton effect on the a
N values, and the intrinsic a
N value of 3 in the ideal gaseous state, respectively. The plots of a
N
versus noncybotactic solvent constants, such as dipolar moment () and dielectric constant (), all show random cases. 相似文献
15.
Lieby Zborovsky Arseni Kostenko Dmitry Bravo‐Zhivotovskii Yitzhak Apeloig 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14666-14670
The E and Z geometric isomers of a stable silene (tBu2MeSi)(tBuMe2Si)Si=CH(1‐Ad) ( 1 ) were synthesized and characterized spectroscopically. The thermal Z to E isomerization of 1 was studied both experimentally and computationally using DFT methods. The measured activation parameters for the 1Z ? 1E isomerization are: Ea=24.4 kcal mol?1, ΔH≠=23.7 kcal mol?1, ΔS≠=?13.2 e.u. Based on comparison of the experimental and DFT calculated (at BP86‐D3BJ/def2‐TZVP(‐f)//BP86‐D3BJ/def2‐TZVP(‐f)) activation parameters, the Z?E isomerization of 1 proceeds through an unusual (unprecedented for alkenes) migration–rotation–migration mechanism (via a silylene intermediate), rather than through the classic rotation mechanism common for alkenes. 相似文献
16.
Hidemasa Azuma Yuzuru Katagiri Shinichi Yamabe 《Journal of polymer science. Part A, Polymer chemistry》1996,34(8):1407-1414
Transition states (TSs) of radical addition homopolymerization reactions of methyl acrylate, methyl methacrylate, dimethyl itaconate, and N-methyl itaconimide were examined with two-unit radical models using MOPAC (PM3 UHF) semiempirical method. Calculated activation energies (Eas) show good correlations with experimental values. Calculated activation entropies (−ΔS‡s) are found to be well proportional to Eas. The entropy terms play an important role as well as Ea in radical additions. Ea depends on the angle (θrs) between reaction points of radical and of monomer at TS. The bond length between reaction points at TS is constant regardless of monomers studied. The geometries and thermodynamical properties calculated here for TS indicate the importance of steric effects caused by substituted group(s) rather than electronic perturbation energies reported previously. © 1996 John Wiley & Sons, Inc. 相似文献
17.
David K. Lewis Timothy Gray Vlad Katsva Kyle Parcella Jessica Schlier Bansi L. Kalra Janet Cho Debra Mish 《国际化学动力学杂志》2006,38(8):483-488
Reaction rates for the structural isomerization of 1,1,2,2‐tetramethylcyclopropane to 2,4‐dimethyl‐2‐pentene have been measured over a wide temperature range, 672–750 K in a static reactor and 1000–1120 K in a single‐pulse shock tube. The combined data from the two temperature regions give Arrhenius parameters Ea=64.7 (±0.5) kcal/mol and log10(A, s?1) = 15.47 (±0.13). These values lie at the upper end of the ranges of Ea and log A values (62.2–64.7 kcal/mol and 14.82–15.55, respectively) obtained from three previous experimental studies, each of which covered a narrower temperature range. The previously noted trend toward lower Ea values for structural isomerization of methylcyclopropanes as methyl substitution increases extends only through the dimethylcyclopropanes (1,1‐ and 1,2‐); Ea then appears to increase with further methyl substitution. In contrast, the pre‐exponential factors for isomerization of cyclopropane and all of the methylcyclopropanes through tetramethylcyclopropane lie within ±0.3 of log10(A, s?1) = 15.2 and show no particular trend with increasing substitution. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 483–488, 2006 相似文献
18.
S. Azhagiri S. Jayakumar R. Padmanaban S. Gunasekaran S. Srinivasan 《Journal of solution chemistry》2009,38(4):441-448
Densities and ultrasonic speeds of binary mixtures of benzaldehyde with n-hexane and cyclohexane at 30 °C were measured over the entire composition range. From these experimental data, the adiabatic
compressibility (K
S
), intermolecular free length (L
f), acoustic impedance (Z), relative association (R
a) and relaxation strength (r) were calculated. Also, the excess adiabatic compressibility (K
S
E), intermolecular free length (L
fE), acoustic impedance (Z
E), and ultrasonic velocity (U
E) were calculated. The observed variation of these parameters helps in understanding the nature of interactions in these mixtures.
Further, theoretical values of the ultrasonic speed were evaluated using theories and empirical relations. The relative merits
of these theories and relations were discussed. 相似文献
19.
The kinetic values of thermal degradation of some steroids were calculated by using TG and DTG curves and the Freeman-Carroll and the Jeres methods. Then andE a values calculated by the Jeres method are more reasonable. The kinetic thermal stabilities of the simple functional groups of the steroids were compared by using theE a values of Jeres, and the following sequences were found: 17β-OH>17-octy 1>17-Ac-CHO>17-keto; 3β-OH> 3-keto>3a-OH; and 5a-H>5β-H>Δ5(6)>Δ4. The k,Z, ΔH*, ΔS* and ΔG* values were calculated at the maximum decomposition rate temperatures by using the Jeres values. The ΔS* values are negative and suggest a high ordering of the transition state. The ΔH* and ΔG* values are positive, as expected. 相似文献
20.
Z. Fengqui H. Rongzu S. Jirong G. Hongxu 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(7):1034-1036
The kinetic parameters of the exothermic decomposition of the title compound in a temperatureprogrammed mode have been studied
by means of DSC. The DSC data obtained are fitted to the integral, differential, and exothermic rate equations by the linear
least-squares, iterative, combined dichotomous, and least-squares methods, respectively. After establishing the most probable
general expression of differential and integral mechanism functions by the logical choice method, the corresponding values
of the apparent activation energy (E
a), preexponential factor (A), and reaction order (n) are obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential
form and the values of E
a and A of this reaction are (1 − α)−4.08, 149.95 kJ mol−1, and 1014.06 s−1, respectively. With the help of the heating rate and kinetic parameters obtained, the kinetic equation of the exothermic
decomposition of the title compound is proposed. The critical temperature of thermal explosion of the compound is 155.71°C.
The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal explosion rule
of the title compound.
The text was submitted by the authors in English. 相似文献