首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol?1, 1013.80 s?1; 108.0 kJ mol?1, 1023.23 s?1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ), enthalpy of activation (ΔH ) and the free energy of activation (ΔG ) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being ?1464.55 ± 1.70 kJ mol?1 by a rotating-bomb calorimeter.  相似文献   

2.
The propulsion of most of the operating satellites comprises monopropellant (hydrazine––N2H4) or bipropellant (monometilydrazine—MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N2H4. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela–Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min?1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol?1, lnA = 14.2 ± 0.9 and T b = 69 °C) and oxygen (E = 64.9 ± 8.6 kJ mol?1, lnA = 20.7 ± 3.1 and T b = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F 1/3 model.  相似文献   

3.
Thermal decomposition of formaldehyde diperoxide (1,2,4,5-tetraoxane) in aqueous solution with an initial concentration of 6.22 × 10?3 M was studied in the temperatures range from 403 to 439 K. The reaction was found to follow first-order kinetic law, and formaldehyde was the major decomposition product. The activation parameters of the initial step of the reaction (ΔH = 15.25 ± 0.5 kcal mol?1, ΔS = ?47.78 ± 0.4 cal mol?1K?1, E a = 16.09 ± 0.5 kcal mol?1) support a mechanism involving homolytic rupture of one peroxide bond in the 1,2,4,5-tetraoxane molecule with participation of the solvent and formation of a diradical intermediate.  相似文献   

4.
Kinetics of two successive thermal decomposition reaction steps of cationic ion exchange resins and oxidation of the first thermal decomposition residue were investigated using a non-isothermal thermogravimetric analysis. Reaction mechanisms and kinetic parameters for three different reaction steps, which were identified from a FTIR gas analysis, were established from an analysis of TG analysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO3H+ from divinylbenzene copolymer was well described by an Avrami–Erofeev type reaction (n = 2, g(α) = [?ln(1 ? α)]1/2]), and its activation energy was determined to be 46.8 ± 2.8 kJ mol?1. Thermal decomposition of remaining polymeric materials at temperatures above 400 °C was described by one-dimensional diffusion (g(α) = α 2), and its activation energy was determined to be 49.1 ± 3.1 kJ mol?1. The oxidation of remaining polymeric materials after thermal dissociation of SO3H+ was described by a phase boundary reaction (contracting volume, g(α) = 1?(1 ? α)1/3). The activation energy and the order of oxygen power dependency were determined to be 101.3 ± 13.4 and 1.05 ± 0.17 kJ mol?1, respectively.  相似文献   

5.
IntroductionCycloureanitramineswithN trinitroethylgroupshaveagreaterdensityandahigherdetonationvelocity .Someofthecompoundscouldbeusedashighexplosives .1,5 Dimethyl 2 ,6 bis(2 ,2 ,2 trinitroethyl)glycoluril (1)isatypicalcycloureanitramine .Thecrystaldensityis1 74g/…  相似文献   

6.
This research aimed to investigate the optimum conditions for modification of thermal decomposition properties of ammonium perchlorate (AP) particles through microencapsulation techniques. A solvent/non-solvent method has been used to perform microencapsulation of AP particles with some polymer-coating agents such as viton A and nitrocellulose (NC). Differential scanning calorimetry, thermogravimetry, and scanning electron microscopy have been exploited to investigate the thermal properties, heat of decomposition, and coating morphology of pure and coated samples. The preliminary results revealed that AP microparticle could be effectively coated with both NC and viton, but the latter significantly and unfavorably attenuated heat of decomposition of AP so NC was chosen as an appropriate coating agent for modification of thermal properties of AP. The thermal analysis of NC-coated samples, prepared at optimized coating conditions, showed that its first stage decomposition temperature increases about 12 °C with respect to uncoated sample and reaches to 305 °C. Also, the apparent activation energy (E), ΔG , ΔH , and ΔS of the decomposition processes of the pure and coated AP particles at the optimum conditions were obtained by non-isothermal methods that proposed by ASTM and Ozawa. Finally, the results of this investigation showed that microencapsulation of AP particles with fibrous NC enhance its heat of decomposition (~120 J g?1) with no obvious effect on kinetic parameters and thermal decomposition temperature.  相似文献   

7.
The complexes of [Sm(o-MOBA)3bipy]2·H2O and [Sm(m-MOBA)3bipy]2·H2O (o(m)-MOBA = o(m)-methoxybenzoic acid, bipy-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, IR, UV, XRD and molar conductance, respectively. The thermal decomposition processes of the two complexes were studied by means of TG–DTG and IR techniques. The thermal decomposition kinetics of them were investigated from analysis of the TG and DTG curves by jointly using advanced double equal-double steps method and Starink method. The kinetic parameters (activation energy E and pre-exponential factor A) and thermodynamic parameters (ΔH , ΔG and ΔS ) of the second-step decomposition process for the two complexes were obtained, respectively.  相似文献   

8.
The mineralogical characterization and pyrolysis kinetics of raw oil shale from Moroccan Rif region and the corresponding bitumen-free material were investigated using various analytical techniques. The structural analysis results showed the siliceous character of mineral matrix and the presence of complex organic components in both oil shales studied. Non-isothermal pyrolysis kinetic measurements indicated that bitumen-free oil shale exhibits a single behavior pyrolysis in the oil-producing stage as compared to raw oil shale. The activation energies estimated by using isoconversional methods reveal that the pyrolysis reaction occurred by one-step kinetic process. The kinetic parameters, determined from a nonlinear fitting method using various kinetic models g(α) and iterative Kissinger–Akahira–Sunose energy calculations, reveal that the pyrolysis mechanism is well described by the nth order kinetics (Fn), with n = 1.071, for bitumen-free oil shale, and n = 1.550, for kerogen of raw oil shale. The mechanism of the whole pyrolysis process of raw oil shale seems not to be affected by the elimination of bitumen, but only some kinetic changes have been recorded in the reaction order mechanism. The process pyrolysis is represented by independent reactions and consequently considered as parallel processes. Besides, the thermodynamic functions of activated complexes (?S , ?H and ?G ) were also calculated and the pyrolysis is found as non-spontaneous process in agreement with the thermal analysis data.  相似文献   

9.
邻苯二胺与5-氯-2-羟基二苯酮、邻香草醛作用合成了一种不对称希夫碱配体C27H21N2O3Cl(H2L)。在正丁醇和甲醇体系中硝酸铀酰与该配体反应合成了一种固体希夫碱配合物[UO2(HL)(NO3)(H2O)]·H2O。通过元素分析、IR、UV、1H NMR、TG-DTG及摩尔电导率分析等手段对合成的配合物进行了表征,用非等温热重法研究了铀(Ⅵ)配合物的热分解反应动力学,推断出第三步热分解的动力学方程为:d α /d t = A · e- E/RT ·3/2[(1- α )-1/3-1]-1,得到了动力学参数E和A。并计算出了活化熵△S¹和活化吉布斯自由能△G¹。  相似文献   

10.
Application of iso-temperature method of multiple rate to kinetic analysis   总被引:2,自引:0,他引:2  
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 E a, the pre-exponential factor A was obtained on the basis of E a and g(α). In this new method, the thermal analysis kinetics triplet of dehydration of calcium oxalate monohydrate is determined, which apparent activation energy E a is 82.83 kJ mol-1, pre-exponential factor A is 1.142·105-1.235·105 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.  相似文献   

11.
The thermal behavior and thermal decomposition kinetic parameters of podophyllotoxin (1) and 4 derivatives, picropodophyllin (2), deoxypodophyllotoxin (3), fl-apopicropodophyllin (4), podophyllotoxone (5) in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for first stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analy- sis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was (1- a)^2 for compounds 1-3,2/3·a^-1/2 for compound 4 and 1/2(1-a)·[-In(1-a)]^-1 for compound 5. The values of Ea indicated that the reactivity of compounds 1-5was increased in the order: 5〈4〈2〈1〈3. The values of the entropy of activation △S^≠, enthalpy of activation △H^≠ and free energy of activation △G^≠ of the reactions were estimated. The values of △G^≠ indicated that the thermal stability of compounds 1-3 with the samef(a) was increased in the order: 2〈3〈1.  相似文献   

12.
The nanosized LiNiPO4 was successfully synthesized by a solid-state reaction between the new Ni3(PO4)2·8H2O precursor and Li3PO4 at 700 °C in air atmosphere. The formation of LiNiPO4 was generated via three thermal decomposition steps. The samples were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, atomic absorption/atomic emission spectrophotometers, and thermogravimetric/differential thermal gravimetric/differential thermal analysis techniques. The activation energy (Eα) values of the three steps were calculated by Vyazovkin method and determined to be 90.39?±?5.79, 197.81?±?7.46, and 308.66?±?12.03 kJ mol?1, respectively. The average Eα values from this method are very close to Eα from KAS method. The most probable mechanism functions g(α) of three steps were evaluated by using the masterplots method and found to be the F1/3 (first step), F3/2 (second step), and D4 (final step), respectively. The pre-exponential factors (A) values of three steps were obtained based on the Eα and g(α). The kinetic triplet parameters of the formation of LiNiPO4 from the new precursor are reported in the first time.  相似文献   

13.
Three linear isoconversional methods (Friedman, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose) and the invariant kinetic parameters (IKP) method were used in order to examine the kinetics of the nonisothermal decomposition of a sodium bicarbonate (NaHCO3). The objective of the paper is to show the usefulness of the IKP method to determine both the kinetic parameters and the kinetic model of the investigated process. The activation energy (Ea) value obtained by the IKP method is in good agreement with the values obtained by isoconversional methods. The IKP method associated with the criterion of coincidence of kinetic parameters for all heating rates led us to the following kinetic triplet: Ea = 95.5 kJ mol?1, A = 2.65 × 1010 min?1, and conversion function f(α) = (1 ? α) (first‐order reaction model, F1). © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 462–471, 2007  相似文献   

14.
The nickel phosphate octahydrate (Ni3(PO4)2·8H2O) was synthesized by a simple procedure and characterized by FTIR, TG/DTG/DTA, AAS, and XRD techniques. The morphologies of the title compound and its decomposition product were studied by the SEM method. The dehydration process of the synthesized hydrate occurred in one step over the temperature range of 120–250 °C, and the thermal decomposition product at 800 °C was found to be Ni3(PO4)2. The kinetic parameters (E and A) of this step were calculated using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E, which confirm the single-step mechanism of the dehydration process. The non-isothermal kinetic method was used to determine the mechanism function of the dehydration, which indicates the contracting disk mechanism of R1 model as the most probable mechanism function and agrees well with the isothermal data. Besides, the isokinetic temperature value (T i) was calculated from the spectroscopic data. The thermodynamic functions of the activated complex (ΔS , ΔH , and ΔG ) of the dehydration process were calculated using the activated complex theory of Eyring. The kinetic parameters and thermodynamic functions of the activated complex for the dehydration process of Ni3(PO4)2·8H2O are reported for the first time.  相似文献   

15.
The copper(II) oxalate was synthesized, characterized using FT-IR and scanning electron microscopy and its non-isothermal decomposition was studied by differential scanning calorimetric at different heating rates. The kinetics of the thermal decomposition was investigated using different isoconversional and maximum rate (peak) methods viz. Kissinger–Akahira–Sunose (KAS), Tang, Starink1.95, Starink1.92, Flynn–Wall–Ozawa (FWO) and Bosewell. The activation energy values obtained from isoconversional methods of FWO and Bosewell are 0.9 and 3.0 %, respectively, higher than that obtained from other methods. The variation of activation energy, E α with conversion function, α, established using these different methods were found to be similar. Compared to the FWO method, the KAS method offers a significant improvement in the accuracy of the E a values. All but the Bosewell maximum rate (peak) methods yielded consistent values of E α (~137 kJ mol?1); however, the complexity of the thermal decomposition reaction can be identified only through isoconversional methods.  相似文献   

16.
The work deals with thermal decomposition of acetyl ferrocene in nitrogen atmosphere based on nonisothermal thermogravimetry. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetic parameters. Model free (integral isoconversional) methods are employed to analyze the thermogravimetric data. The decomposition is a multistep process. The activation energy Eα of decomposition is conversion (α) dependent. The average values of activation energy are Eα = 49.87, 106.28, and 183.35 kJ mol−1 for three major steps of decomposition. The most probable reaction mechanism function, g(α), for thermal reactions has been identified by the master plot method, and the stepwise reaction mechanisms are found to be different for different steps. The estimated values of the activation energy Eα and g(α) have been utilized in the determination of the reaction rate Aα of thermal decomposition. The α‐dependent reaction rate values are determined and are found to lie in the range of 5.2 × 105 to 3.2 × 104 min−1, 1.7 × 1015 to 7.8 × 106 min−1, and 3.8 × 108 to 1.4 × 107 min−1 for three different steps. Based on the values of Eα, g(α), and Aα, the thermodynamic triplets (ΔS, ΔH, ΔG) associated with the decomposition reactions have been estimated. Estimated kinetic parameters have been used to construct the conversion curves, and those have been successfully compared with the experimentally observed ones.  相似文献   

17.
Ligand substitution kinetics for the reaction [PtIVMe3(X)(NN)]+NaY=[PtIVMe3(Y)(NN)]+NaX, where NN=bipy or phen, X=MeO, CH3COO, or HCOO, and Y=SCN or N3, has been studied in methanol at various temperatures. The kinetic parameters for the reaction are as follows. The reaction of [PtMe3(OMe)(phen)] with NaSCN: k1=36.1±10.0 s−1; ΔH1=65.9±14.2 kJ mol−1; ΔS1=6±47 J mol−1 K−1; k−2=0.0355±0.0034 s−1; ΔH−2=63.8±1.1 kJ mol−1; ΔS−2=−58.8±3.6 J mol−1 K−1; and k−1/k2=148±19. The reaction of [PtMe3(OAc)(bipy)] with NaN3: k1=26.2±0.1 s−1; ΔH1=60.5±6.6 kJ mol−1; ΔS1=−14±22 J mol−1K−1; k−2=0.134±0.081 s−1; ΔH−2=74.1±24.3 kJ mol−1; ΔS−2=−10±82 J mol−1K−1; and k−1/k2=0.479±0.012. The reaction of [PtMe3(OAc)(bipy)] with NaSCN: k1=26.4±0.3 s−1; ΔH1=59.6±6.7 kJ mol−1; ΔS1=−17±23 J mol−1K−1; k−2=0.174±0.200 s−1; ΔH−2=62.7±10.3 kJ mol−1; ΔS−2=−48±35 J mol−1K−1; and k−1/k2=1.01±0.08. The reaction of [PtMe3(OOCH)(bipy)] with NaN3: k1=36.8±0.3 s−1; ΔH1=66.4±4.7 kJ mol−1; ΔS1=7±16 J mol−1K−1; k−2=0.164±0.076 s−1; ΔH−2=47.0±18.1 kJ mol−1; ΔS−2=−101±61 J mol−1 K−1; and k−1/k2=5.90±0.18. The reaction of [PtMe3(OOCH)(bipy)] with NaSCN: k1 =33.5±0.2 s−1; ΔH1=58.0±0.4 kJ mol−1; ΔS1=−20.5±1.6 J mol−1 K−1; k−2=0.222±0.083 s−1; ΔH−2=54.9±6.3 kJ mol−1; ΔS−2=−73.0±21.3 J mol−1 K−1; and k−1/k2=12.0±0.3. Conditional pseudo-first-order rate constant k0 increased linearly with the concentration of NaY, while it decreased drastically with the concentration of NaX. Some plausible mechanisms were examined, and the following mechanism was proposed. [Note to reader: Please see article pdf to view this scheme.] © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 523–532, 1998  相似文献   

18.
The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N‐N‐bis[N‐(2,2,2‐tri‐nitroethyl)‐N‐nitro]ethylenediamine in a temperature‐programmed mode have been investigated by means of differential scanning calorimetry (DSC). The results show that kinetic model function in differential form, apparent activation energy Ea and pre‐exponential factor A of this reaction are 3(1 ‐α)2/3, 203.67 kJ·mol?1 and 1020.61s?1, respectively. The critical temperature of thermal explosion of the compound is 182.2 °C. The values of ΔS ΔH and ΔG of this reaction are 143.3 J·mol?1·K?1, 199.5 kJ·mol?1 and 135.5 kJ·mol?1, respectively.  相似文献   

19.
The dimer-monomer reactions were investigated for the system cis and transo,o'-azodioxytoluene-o-nitrosotoluene in acetonitrile solvent. For the reaction cis dimer-monomer the following thermodynamic and activation parameters have been derived: ΔH°=58.5±2.5 kJ mole?1, ΔS°=206.2±3.8 J mole?1 K?1, ΔH=63.6±3.3 kJ mole?1, ΔS=6.3±0.3 J mole?1 K?1. The corresponding values for the reaction trans dimer-monomer are: ΔH°=45.6±2.1 kJ mole?1, ΔS°=162.7±7.1 J mole?1 K?1, ΔH=80.8±2.9 kj mole?1, ΔS=-13.4±0.8 mole?1 K?1. There is no evidence of a direct cis-trans isomerization (i.e. a reaction not proceeding via the monomer). NMR and various perturbation techniques monitoring the visible absorption of the monomer were employed.  相似文献   

20.
The boiling point and volatility are important properties for fuels, as it is for quality control of the industry of petroleum diesel and biofuels. In addition, through the volatility is possible to predict properties, such as vapor pressure, density, latent heat, heat of vaporization, viscosity, and surface tension of biodiesel. From thermogravimetry analysis it is possible to find the kinetic parameters (activation energy, pre-exponential factor, and reaction order), of thermally simulated processes, like volatilization. With the kinetic parameters, it is possible to obtain the thermodynamic parameters by mathematical formula. For the kinetic parameters, the minor values of activation energy were found for mineral diesel (E = 49.38 kJ mol?1), followed by babassu biodiesel (E = 76.37 kJ mol?1), and palm biodiesel (E = 87.00 kJ mol?1). Between the two biofuels studied, the babassu biodiesel has the higher minor value of activation energy. The thermodynamics parameters of babassu biodiesel are, ΔS = ?129.12 J mol?1 K?1, ΔH = +80.38 kJ mol?1 and ΔG = +142.74 kJ mol?1. For palm biodiesel ΔS = ?119.26 J mol?1 K?1, ΔH = + 90.53 kJ mol?1 and ΔG = +141.21 kJ mol?1, and for diesel ΔS = ?131.3 J mol?1 K?1, ΔH = +53.29 kJ mol?1 and ΔG = +115.13 kJ mol?1. The kinetic thermal analysis shows that all E, ΔH, and ΔG values are positive and ΔS values are negative, consequently, all thermodynamic parameters indicate non-spontaneous processes of volatilization for all the fuels studied.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号