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1.
The kinetic scheme for ozone decomposition in an aqueous solution in a wide pH interval was proposed on the basis of the known
literature data. The apparent first-order rate constant for ozone decomposition at pH 1–14 was calculated.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1151–1156, June, 2008. 相似文献
2.
L. I. Giménez J. M. Romero S. Bustillo N. L. Jorge M. E. Gómez Vara E. A. Castro 《Russian Journal of General Chemistry》2008,78(6):1273-1276
Thermal decomposition of 3,3,6,6-tetramethyl-1,2,4,5-tetraoxane was examined in methanol solution (1.69×10−2 M) containing cuprous ions (5.05×10−7 M) in the temperature range from 130 to 166°C using UV spectroscopy as analytical method. The ion-catalyzed reaction follows
first-order kinetics with respect to the peroxide and added cuprous ions. The temperature effect on the rate of thermal decomposition
of the title compound was described by the corresponding Arrhenius equations, and its stability in solution was estimated
on a quantitative level. The activation parameters of the initial step of decomposition of 3,3,6,6-tetramethyl-1,2,4,5-tetraoxane
were determined (ΔH
≠ = 14.7±0.8 kcal mol−1; ΔS
≠ = −38.9±1.4 cal mol−1 K−1; ΔG
≠ = 31.0±0.8 kcal mol−1). Electron-transfer mechanism was proposed for the reaction under study.
The text was submitted by the authors in English. 相似文献
3.
Non-isothermal Studies on Mechanism And Kinetics of Thermal Decomposition of Cobalt(II) Oxalate Dihydrate 总被引:1,自引:0,他引:1
B. Małecka E. Drożdż-Cieśla A. Małecki 《Journal of Thermal Analysis and Calorimetry》2002,68(3):819-831
Thermal decomposition of CoC2O4⋅2H2O was studied using DTA, TG, QMS and XRD techniques. It was shown that decomposition generally occurs in two steps: dehydration
to anhydrous oxalate and next decomposition to Co and to CoO in two parallel reactions. Two parallel reactions were distinguished
using mass spectra data of gaseous products of decomposition. Both reactions run according toAvrami–Erofeev equation. For
reaction going to metallic cobalt parameter n=2 and activation energy is 97±14 kJ mol–1. It was found that decomposition to CoO proceeds in two stages. First stage (0.12<αII<0.41) proceeds according to n=2, with activation energy 251±15 kJ mol–1 and second stage (0.45<αII<0.85) proceeds according to parameter n=1 and activation energy 203±21 kJ mol–1.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Fluoride occurs in some drinking water sources at levels that are hazardous to health. Tests were conducted to assess the
ability of a mineral-based adsorbent to take-up fluoride ion. Consequently, in search of novel adsorbent media, crystalline
and hydrous iron(III)-zirconium(IV) hybrid oxide (IZHO) was synthesized, and tested to determine its capacity and kinetics
for fluoride adsorption. The Fourier Transform Infrared (FTIR) spectrum of IZHO indicated the presence of Fe–O–Zr linkage
which showed hybrid nature of the synthetic oxide. The optimum pH range for fluoride adsorption was ranged between 4.0 and
7.0. The analyses of the isotherm equilibrium data using the Langmuir and the Redlich–Peterson model equations by linear and
non-linear methods showed that the data fitted better with latter model than the former. Thermodynamic analysis showed spontaneous
nature of fluoride adsorption, and that took place with the increase of entropy. The kinetic data obtained for fluoride adsorption
on IZHO at pH 6.8 (±0.1) and room temperature (303±2 K) described both the pseudo-first order and the reversible first-order
equations equally well (r
2= ∼0.98–0.99), and better than pseudo second order equation (r
2= ∼0.96–0.98) for higher concentrations (12.5 and 25.0 mg/dm3) of fluoride. The kinetics of fluoride adsorption on the mixed oxide took place with boundary layer diffusion. External mass
transport with intra-particle diffusion phenomena governed the rate limiting process, which has been confirmed from the Boyd
poor non-linear kinetic plots. 相似文献
5.
Yan Shi Xiancheng Zhan Lie Ma Linli Li Chengrong Li 《Frontiers of Chemistry in China》2007,2(2):140-145
An evaluation method for the capacity of antioxidants to protect drugs against oxidation is presented. As a new viewpoint,
to determine the priority of the competitive oxidations between the antioxidant and the protected drug, and to compare the
drug-protection capacity of antioxidants, it is important to determine their oxidation rate constants using chemical kinetics
instead of standard oxidation (or reduction) potentials. Sodium sulfite, sodium bisulfite and sodium pyrosulfite were used
as models for the determination of oxidation reaction rate constants in aqueous solutions. In the experiments, sufficient
air was continually infused into the solution to keep the concentration of dissolved oxygen constant. The residual concentrations
of the antioxidants were determined by iodimetry, and the concentration of dissolved oxygen by oxygen electrode. The data
were fitted by linear regressions to obtain the reaction rate constants. It was found that the degradation of sodium sulfite,
sodium bisulfite or sodium pyrosulfite obeyed pseudo zero-order kinetics in the buffer solutions. Because of the ionization
equilibrium, these three antioxidants have the same ion form in solutions at a definite pH value and therefore their apparent
rate constants were essentially the same. The average apparent rate constants of the three antioxidants at 25°C are (1.34
± 0.03) × 10−3 at pH 6.8, (1.20 ± 0.02) × 10−3 at pH 4.0 and (6.58 ± 0.02) × 10−3 mol·L−1·h−1 at pH 9.2, respectively.
Translated from Acta Chimica Sinica, 2006, 64(6): 496–500 (in Chinese) 相似文献
6.
Jiankun Xie Qinyan Yue Hui Yu Wenwen Yue Renbo Li Shengxiao Zhang Xiaona Wang 《Frontiers of Chemistry in China》2008,3(1):33-40
Activated carbon was prepared from the sewage sludge of municipal wastewater treatment plant by chemical activation (activation
reagent is ZnCl2) and was used for the adsorption of dye (reactive brilliant red K-2BP). The impact of adsorbent amount, adsorption time and
pH value on adsorption effect, the adsorption kinetics, and the adsorption thermodynamics were discussed according to batch
adsorption tests. The results indicated that the activated carbon developed from sewage sludge (ACSS), which was mesoporous,
possessed opened porous structures. The iodine number of the ACSS was 326 mg·g−1. The rate of achievement was 51.31%. The BET surface area was 298 m2·g−1 and the contents of heavy metals in the leachate didn’t exceed the contents limit. The adsorption kinetics of reactive brilliant
red K-2BP on the ACSS was accorded with the two-step kinetics rate equation and pseudo-second-order kinetics equation. Compared
to the Freundlich isotherm equation, the Langmuir isotherm equation showed better applicability for the adsorption. The adsorption
which was favorable was an endothermic (enthalpy ΔH > 0) and spontaneous (free energy ΔG < 0) process and was accompanied by an increase in entropy (ΔS > 0).
__________
Translated from Journal of Shandong University (Natural Science), 2007, 42(3): 64–70 [译自: 山东大学学报(理学版)] 相似文献
7.
The kinetics of radical decomposition of di(tert-butyl) trioxide was studied by spectrophotometry from the consumption of an acceptor of free radicals, 2,6-di(tert-butyl)-4-methylphenol, in CFCl3 and CH2Cl2 (in the latter case, in the presence of 0.1M ButOOH). The activation parameters of the reaction (log(A/s
−1)=14.8±1.2 and 14.1±1.6,E
a=21.6±1.4 and 20.1±1.9 kcal mol−1 in CFCl3 and CH2Cl2, respectively) and the probability of radical escape to the bulk (e=0.9±0.1) were determined. The known experimental and calculated values of the O−OO bond strength in trioxides were analyzed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 61–65, January, 1999. 相似文献
8.
The kinetics of Li2SO4·H2O dehydration in static air atmosphere was studied on the basis of nonisothermal measurements by differential scanning calorimetry.
Dehydration data were subjected to an integral composite procedure, which includes an isoconversional method, a master plots
method and a model-fitting method. Avrami-Erofeev equation was found to describe all the experimental data in the range of
conversion degrees from 0.1 to 0.9. The determined activation energy equals 65.45 kJ·mol−1 with standard deviation ±0.47 kJ·mol−1. The estimated value of parameter m in Avrami-Erofeev equation is 2.15 with standard deviation ±0.11. Also, the obtained pre-exponential factor is 7.79×105 s−1 with standard deviation ±0.55×105 s−1. The results show that the present integral composite procedure gives self-consistent kinetic parameters. 相似文献
9.
F Xu L X Sun Z C Tan J G Liang T Zhang 《Journal of Thermal Analysis and Calorimetry》2006,83(1):187-191
Molar heat capacities
of acetaminophen were precisely measured with a small sample precision automated
adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid
transition at 149.96 K was found from the Cp,m-T curve. The polynomial functions of Cp,.m(J
K-1 mol-1) vs. T were established
on the heat capacity measurements by means of the least square fitting method.
Thermal decomposition
processes of acetaminophen have been studied by thermogravimetry. And the
thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A
and reaction order n, were calculated by
TG-DTG techniques with the Freeman-Carroll method, Kissinger method
and Ozawa method. Accordingly the thermal decomposition kinetics equation
of acetaminophen is expressed as: dα/dt=2.67·107e-89630/RT(1-α)0.23.
The process of fusion has been investigated through
DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.89±0.04)
K, 26.49±0.44 kJ mol-1 and 59.80±1.01
J K-1 mol-1,
respectively. 相似文献
10.
QI Bin YANG Bing WANG ZhuQing YANG HongYan & LIU Lu School of Chemistry Material Sciences Shaanxi Normal University Xi’an China 《中国科学B辑(英文版)》2009,52(3):356-361
Radical production in the ozonolysis of propene in air was monitored directly by a peroxy radical chemical amplification (PERCA) instrument at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The ozonolysis reactions were conducted in a flow tube under pseudo-first-order conditions for ozone. The decay in ozone was calculated based on reaction time tr and effective rate constant keff (keff = k1[C3H6]0)) for the ozone-propene reaction. The total radical yields relative to consumed ozone were d... 相似文献
11.
P. J. Herley C. S. Wang G. Varsi P. W. Levy 《Journal of Thermal Analysis and Calorimetry》1994,41(2-3):435-448
The thermal decomposition kinetics of irradiated and unirradiated ammonium perchlorate and ammonium perchlorate powder-aluminum
particle mixtures has been studied by determining decomposition gas pressurevs. heating time with samples at a controlled temperature Qualitatively the radiation induced changes are similar to those obtained
in previous studies on ‘pure’ ammonium perchlorate. The induction period is shortened and the acceleratory and decay period
rate constants are increased. The data have been analyzed using Avrami-Erofeev kinetics. The results for pure unirradiated
material are in accord with published results. The activation energies for the induction, acceleratory and decay periods for
pure pellets were found to be 133.5±6.7, 131.8±6.7 and 127.2±6.7 kJ·mol, respectively. Samples were exposed to either a single
gamma-ray irradiation, fission neutron irradiation followed by a gamma-ray irradiation, or to a proton irradiation. When compared
on an equal energy deposited basis, the fast neutron induced changes are appreciably larger than the gamma-ray changes. However,
the proton induced changes are comparable or slightly more than the gamma-ray effects. Some, or all, of the fast neutron effects
can be attributable to the concentrated radiation damage ‘spikes’ along the path of lattice atom recoils. It is likely that
these become thermal decomposition sites when the crystals are heated. Protons create fewer spikes than fast neutrons. Overall,
the results indicate that any ammonium perchlorate-aluminum propellant mixtures that may be exposed to radiation environments,
such as used in this study, should be subjected to a thorough radiation effects analysis if reliable performance is required.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献
12.
A. F. Santos L. Polese M. S. Crespi C. A. Ribeiro 《Journal of Thermal Analysis and Calorimetry》2009,96(1):287-291
The non-isothermal data given by TG curves for poly(3-hydroxybutyrate) (PHB) were studied in order to obtain a consistent
kinetic model that better represents the PHB thermal decomposition. Thus, data obtained from the dynamic TG curves were suitably
managed in order to obtain the Arrhenius kinetic parameter E according to the isoconversional F-W-O method. Once the E parameters is found, a suitable logA and kinetic model (f(α)) could be calculated. Hence, the kinetic triplet (E±SD, logA±SD and f(α)) obtained for the thermal decomposition of PHB under non-isothermal conditions was E=152±4 kJ mol−1, logA=14.1±0.2 s−1 for the kinetic model, and the autocatalytic model function was: f(α)=αm(1−α)n=α0.42(1−α)0.56. 相似文献
13.
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
14.
Ll Abia X. L. Armesto M. Canle L. M. V. García M. Losada J. A. Santaballa 《国际化学动力学杂志》1994,26(10):1041-1053
This article analyzes the kinetics of the decomposition of N-Cl-Valine in aqueous solution, which is formed rapidly by chlorination of Valine with sodium hypochlorite. A general-base catalyzed process not yet described is reported. The experimental evidence shows two competitive decomposition paths: an unimolecular concerted fragmentation process (k = (1.8 ± 0.1) · 10?4 s?1 at 298 K) and the other one is an E2 elimination process whose importance increases with pH and depends on the nature and the concentration of the bases present in the medium. © 1994 John Wiley & Sons, Inc. 相似文献
15.
The Effect of pH on Continuous Biohydrogen Production from Swine Wastewater Supplemented with Glucose 总被引:1,自引:0,他引:1
Yecong Li Jun Zhu Xiao Wu Curtis Miller Liang Wang 《Applied biochemistry and biotechnology》2010,162(5):1286-1296
The effect of pH on hydrogen production from liquid swine manure supplemented with glucose by a mixed culture of fermentative
bacteria in an anaerobic sequencing batch reactor was evaluated in this study. At 37 ± 1 °C, five pH values ranging from 4.7
to 5.9 at an increment of 0.3 were tested at a hydraulic retention time (HRT) of 16 h. The results showed that at this HRT,
the optimal pH for hydrogen production was 5.0, under which the biogas comprised 33.57 ± 5.65% of hydrogen with a production
rate of 8.88 ± 2.94 L-H2/day and a yield of 1.48 ± 0.49 L-H2/L liquid swine manure. The highest biomass concentration, highest butyric acid to acetic acid ratio, lowest propionic acid
concentration, and the best stability were all found at pH 5.0, while the highest CH4 productivity was found at pH 5.9. For efficient hydrogen production, oxygen content should be controlled under 2%, beyond
which an inverse linear relationship (R
2 = 0.986) was observed. 相似文献
16.
David Siegel Stefan Merkel Wolfram Bremser Matthias Koch Irene Nehls 《Analytical and bioanalytical chemistry》2010,397(2):453-462
The degradation kinetics of the Alternaria mycotoxin tenuazonic acid (l-TA) in aqueous buffer were studied over a period of 4 months at different pH levels (3.5 and 7.0) and temperatures (4, 25
and 40 °C). l-TA and its degradation products were quantified by newly developed high-performance liquid chromatography methods with UV
or electrospray multistage mass spectrometry detection. At pH 3.5, significant degradation occurred at 25 and 40 °C, the respective
l-TA half-lives being 73.8 ± 0.4 and 14.0 ± 0.1 days. Two degradation processes, epimerization and hydrolysis, were evaluated
kinetically. The hydrolytically formed iso-deacetyl TA (iso-DTA, epimeric mixture) was found to be the stable end product of l-TA degradation under the conditions of this study. This indicates that iso-DTA as well as the l-TA epimer u-TA are formed in aqueous beverage matrices. 相似文献
17.
Luciana S. Guinesi C. A. Ribeiro Marisa S. Crespi A. F. Santos Marisa V. Capela 《Journal of Thermal Analysis and Calorimetry》2006,85(2):301-307
This work aims the evaluation of the kinetic triplets
corresponding to the two successive steps of thermal decomposition of Ti(IV)–ethylenediaminetetraacetate
complex. Applying the isoconversional Wall–Flynn–Ozawa method
on the DSC curves, average activation energy: E=172.4±9.7
and 205.3±12.8 kJ mol–1, and pre-exponential
factor: logA=16.38±0.84 and 18.96±1.21
min–1 at 95% confidence interval could be
obtained, regarding the partial formation of anhydride and subsequent thermal
decomposition of uncoordinated carboxylate groups, respectively.
From E and logA values,
Dollimore and Málek methods could be applied suggesting PT (Prout–Tompkins)
and R3 (contracting volume) as the kinetic model to the partial formation
of anhydride and thermal decomposition of the carboxylate groups, respectively. 相似文献
18.
Kinetic
parameters determination in non-isothermal conditions for the crystallisation
of a silica-soda-lead glass 总被引:1,自引:0,他引:1
Oana Cătălina Mocioiu Maria Zaharescu Georgeta Jitianu P. Budrugeac 《Journal of Thermal Analysis and Calorimetry》2006,86(2):429-436
Two integral isoconversional methods (Flynn–Wall–Ozawa and
Kissinger–Akahira–Sunose) and the invariant kinetic parameters
method (IKP) were used in order to examine the kinetics of the non-isothermal
crystallisation of a silica-soda-lead glass. The objective of the paper is
to show the usefulness of the IKP method to determine both the activation
parameters and the kinetic model of the investigated process. Thismethod associated
with the criterion of coincidence of kinetic parameters for all heating rates
and some procedures of the evaluation of the parameter from Johnson–Mehl–Avrami–Erofeev–Kolmogorov
(JMAEK) equation led us to the following kinetic triplet: activation energy, E=170.5±2.5 kJ mol–1
, pre-exponential factor, A=1.178±0.350·10
10 min–1 and JMAEK model (A
m) m=1.5. 相似文献
19.
Banjong Boonchom 《Journal of Thermal Analysis and Calorimetry》2009,98(3):863-871
The thermal decomposition of magnesium hydrogen phosphate trihydrate MgHPO4 · 3H2O was investigated in air atmosphere using TG-DTG-DTA. MgHPO4 · 3H2O decomposes in a single step and its final decomposition product (Mg2P2O7) was obtained. The activation energies of the decomposition step of MgHPO4 · 3H2O were calculated through the isoconversional methods of the Ozawa, Kissinger–Akahira–Sunose (KAS) and Iterative equation,
and the possible conversion function has been estimated through the Coats and Redfern integral equation. The activation energies
calculated for the decomposition reaction by different techniques and methods were found to be consistent. The better kinetic
model of the decomposition reaction for MgHPO4 · 3H2O is the F
1/3 model as a simple n-order reaction of “chemical process or mechanism no-invoking equation”. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the decomposition reaction are calculated by the activated complex theory and indicate that the process is non-spontaneous
without connecting with the introduction of heat. 相似文献
20.
The alterations of organic acids citrate, α-ketoglutarate, succinate, fumarate, malate production together with isocitrate
lyase activity as a glyoxalate shunt enzyme, and antibiotic production of Streptomyces sp M4018 were investigated in relation to changes in the glucose, glycerol and starch concentrations (5–20 g/L) after identification
as a strain of Streptomyces hiroshimensis based on phenotypic and genotypic characteristics. The highest intracellular citrate and α-ketoglutarate levels in 20 g/l
of glucose, glycerol, and starch mediums were 399.47 ± 4.78, 426.93 ± 6.40, 355.84 ± 5.38 ppm and 444.81 ± 5.12, 192.96 ± 2.26,
115.20 ± 2.87 ppm, respectively. The highest succinate, malate, and fumarate levels were also determined in 20 g/l of glucose
medium as 548.9 ± 11.21, 596.15 ± 8.26, and 406.42 ± 6.59 ppm and the levels were significantly higher than the levels in
glycerol and starch. Extracellular organic acid levels measured also showed significant correlation with carbon source concentrations
by showing negative correlation with pH levels of the growth medium. The antibiotic production of Streptomyces sp. M4018 was also higher in glucose medium as was the case also for organic acids when compared with glycerol. On the other
hand, there is no production in starch. 相似文献