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1.
利用密度泛函理论直接动力学方法研究了反应CH 3OCF 2CF 2OCH 3+Cl的微观机理和动力学性质. 在BB1K/6-31+G(d,p)水平上获得了反应的势能面信息, 计算中考虑了反应物CH 3OCF 2CF 2OCH 3两个稳定构象(SC1和SC2)的氢提取通道和取代反应通道. 利用改进的正则变分过渡态理论结合小曲率隧道效应(ICVT/SCT)计算了各氢提取通道的速率常数, 进而根据Boltzmann配分函数得到总包反应速率常数(k T)以及每个构象对总反应的贡献. 结果表明296 K温度下计算的k T(ICVT/SCT)值与已有实验值符合得很好. 由于缺乏其他温度速率常数的实验数据, 我们预测了该反应在200-2000 K温度区间内反应速率常数的三参数表达式: k T=0.40×10 -14T 1.05exp(-206.16/T). 相似文献
2.
研究指出表观二级动力学方程可以很好地描述N-异丙基丙烯酰胺水凝胶的溶胀和消溶胀动力学.即溶胀动力学方程为dR/dt=k 1(R e-R) 2,消溶胀动力学方程为-dR/dt=k c(R-R e) 2.把这种水凝胶用于分离高分子水溶液时可引入“单位溶张比分离循环的合理时耗”这样一个参量.它根据溶胀和消溶胀过程中的起始溶胀比、平衡溶胀比、表观溶胀动力学常数和表观消溶胀动力学常数求出.具体公式为△t 1(T s,T c)=2/[R c(T s)-R 0(T s)] 2k s(T s)+15/[R 0(T c)- R s(T c)] 2k c(T c) 1/2在理想情况下,分离过程的“总合理时耗”与△t_1成正比,比例系数为分离过程中的除水总量与干凝胶用量的比值,即△t r=W W/WG·△t 1.当根据二个动力学方程求得的总时耗计算值处于(0.9△t r,1.1△t r)范围内时,表明所选干凝胶用量和循环溶胀比区段均合适. 相似文献
3.
确定了具有层状钙钛矿结构,脂肪链C原子数从12到18四氯合锌酸二烷基铵(C nH 2n+1NH 3) 2ZnCl 4系列化合物的非等温固-固相变动力学。采用Kissinger和Ozawa两种动力学模型,对不同温度下测定的每个样品DSC热分析曲线进行数据处理,计算固-固相变过程的活化能E a。实验结果表明,随着C原子数的增加,脂肪链的有序度和刚度降低,导致固-固相变活化能E a随C原子数的增大而降低。两种模型方法的计算活化能E a的结果相一致。并且各个化合物的固-固相变反应级数不随升温速率和烷基链长变化而变化,总保持为1。 相似文献
4.
借助不同加热速率(β)的非等温DSC曲线离开基线的初始温度(T 0)、onset温度(T e)和峰顶温度(T p), Kissinger法和Ozawa法求得的热分解反应的表观活化能(E k和E O)和指前因子(A k), Hu-Zhao-Gao方程ln β i=ln[A 0/(b e0 or p0G(α))]+ b e0 or p0T ei or pi求得的b e0 or p0, Zhao-Hu-Gao方程ln β i=ln[A 0/((a e0 or p0+1)G(α))]+(a e0 or p0+1) ln T ei or pi求得的a e0 or p0, 微热量法确定的比热容(C p), 以及密度(ρ)、热导率(λ)和分解热(Q d, 取爆热之半)数据, Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式、Zhao-Hu-Gao公式、Smith方程、Friedman公式和Bruckman-Guillet公式, 计算了TNAZ在β→0时的T 0, T e和T p值(T 00, T eo和T p0)、热爆炸临界温度(T be和T bp)、绝热至爆时间(t Tlad)、撞击感度50%落高(H 50)和热点起爆临界温度(T cr), 得到了评价TNAZ热安全性的结果: T SADT=T e0=485.81 K, T p0=497.38 K, T beo=499.50 K, T bp0=513.45 K, t Tlad=8.90 s (n=0), t Tlad=8.96 s (n=1), t Tlad=9.01 s (n=2), H 50=28.88 cm, T cr=641.46 K (T room=293.15 K), T cr=658.89 K (T room=300 K), 表明: (1) TNAZ对热是稳定的; (2)撞击感度好于环三亚甲基三硝胺(RDX); (3)热点起爆临界温度高于RDX, 而界于1,3,5-三氨基-2,4,6-三硝基苯(TATB)和六硝基茋(HNS)之间. 相似文献
5.
本文设计合成了两种以聚吡唑硼酸盐、吡唑为配体的铜配合物Cu 2[ μ-pz] 2[HB(pz) 3] 2( 1)和Cu[B(pz) 4] 2( 2)(pz:吡唑(C 3H 4N 2))。运用元素分析、红外光谱对配合物进行了表征,并用X-ray衍射测定了它们的晶体结构。非等温热分解动力学研究表明:配合物 1的热分解反应分两步,配合物 2的热分解反应一步进行。通过计算,配合物 1热分解的第一步反应的可能机理为成核与生长, n=1/4;第二步反应的可能机理为化学反应。其非等温动力学方程分别为:dα/d T=A/β e -E/RT·1/4(1-α)[-ln(1-α)] -3和dα/d T=A/β e -E/RT·(1-α) 2。分解反应的表观活化能分别是520.37 kJ·mol -1和149.65 kJ·mol -1;指前因子ln A分别是118.06 s -1和28.10 s -1。配合物 2热分解的可能机理为化学反应。其非等温动力学方程为:dα/d T=A/β e -E/RT·(1-α) 2。分解反应的表观活化能是111.41 kJ·mol -1;指前因子ln A是21.20 s -1。 相似文献
6.
用非等温热重法研究了Eu(III)的化合物[Eu(C 10H 9N 2O 4)(C 10H 8N 2O 4)(H2O) 3] 2·phen·4H 2O 的热分解及其动力学,并用Kissinger和Ozawa 方法计算了第一分解阶段的活化能. 相似文献
7.
本文采用晶格模型,以动力学链段长度作为统计单元大小,推导了高聚物玻璃化温度T_8和链静态刚性因子σ 2(T 8),链动态刚性因子β(T 8)以及聚合度DP等分子参数之间的关系。具体讨论了链柔性对T 8的影响。理论预测和几十种聚合物的实验数据能较好吻合,分析结果表明T 8值基本上取决于高聚物链σ(T 8)大小。 相似文献
8.
制备了含3,6-双(1-氢-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪(BTATz)铅复合物(LCBTATZ)的双基推进剂和改性双基推进剂. 采用热重-微商热重法(TG-DTG)及差示扫描量热法(DSC)研究了其热分解行为和非等温分解动力学并在此基础上评价了其热安全性. 结果表明, LCBTATz-DB复合物中在350-540 K之间只存在一个放热分解峰, LCBTATz-CMDB复合物中存在两个连续的放热分解峰在390-540 K温度范围内, 其机理方程分别为: f(α)=α -1/2和f(α)=2(1-α) 3/2. 计算了热加速分解温度(T SADT)、热爆炸临界温度(T b)、热点火温度(T TIT)和绝热至爆时间(t Tlad),其值分别为: DB001复合物T SADT=444.50 K, T TITT=453.96 K, T b=471.84 K; t Tlad=39.36 s; CMDB100复合物, T SADT=442.38 K, T TITT=452.89 K,T b=464.13 K,t Tlad=21.3 s,并以此来评价化合物的热安全性. 考察了LCBTATz-DB以及LCBTATz-CMDB的燃烧性能, 结果表明LCBTATZ 是一种高效的双基燃烧催化剂, 在较大的压力范围内可以显著的提高燃速并且大幅度的降低压力指数. 对于双基推进剂在2-8 MPa压力范围内出现了明显的超燃速现象, 8-12 MPa出现了“麦撒”效应, 对于改性双基推进剂的压力指数降到0.18. 相似文献
9.
采用差示扫描量热法(DSC)、热重和微分热重(TG-DTG)及固相原位反应池/快速扫描傅立叶变换红外联用技术(hyphenated in situ thermolysis/RSFTIR)研究了纳米结晶体Ni 0.5Zn 0.5Fe 2O 4与高氯酸铵(AP)组成的混合物的热行为和分解反应动力学。结果表明:Ni 0.5Zn 0.5Fe 2O 4使得AP的低、高温分解放热峰温分别提前17.44 K和27.74 K,并使得对应的分解热分别增加3.7 J·g -1和193.7 J·g -1。Ni 0.5Zn 0.5Fe 2O 4并不影响AP的晶转温度和晶转热。Ni 0.5Zn 0.5Fe 2O 4使得AP的TG曲线出现3个阶段,并使得后2个失重阶段的初始和终止温度都有所提前。凝聚相分解产物分析表明Ni 0.5Zn 0.5Fe 2O 4加速了凝聚相AP的分解及氨气的释放。含Ni 0.5Zn 0.5Fe 2O 4的AP的高温分解反应的动力学参数 Ea=238.88 kJ·mol -1, A=1018.59 s -1,动力学方程可表示为d α/d t=10 18.99(1- α)[-ln(1- α)] 3/5e -2.87×104T。始点温度( Te)和峰顶温度( Tp)计算得出AP的热爆炸临界温度值分别为:574.83 K和595.41 K。分解反应的活化熵(Δ S≠)、活化焓(Δ H≠)和活化能(Δ G≠)分别为:109.61 J·mol -1·K -1、236.49 kJ·mol -1及172.58 kJ·mol -1。 相似文献
10.
为应用热爆炸临界温升速率(dT/dt) Tb评价含能材料(EMs)的热安全性, 得到计算(dT/dt) Tb值的基本数据, 用合理的假设, 由Semenov的热爆炸理论和9 个自催化反应速率方程[dα/dt=Aexp(-E/RT)α(1-α) (I), dα/dt=Aexp(-E/RT)(1-α) n(1+K catα) (II), dα/dt=Aexp(-E/RT)[α a-(1-α) n)] (III), dα/dt=A 1exp(-E a1/RT)(1-α)+A 2exp(-E a2/RT)α(1-α) (IV), dα/dt=A 1exp(-E a1/RT)(1-α) m+A 2exp(-E a2/RT)α n(1-α) p (V), dα/dt=Aexp(-E/RT)(1-α) (VI), dα/dt=Aexp(-E/RT)(1-α) n (VII), dα/dt=A 1exp(-E a1/RT)+A 2exp(-E a2/RT)(1-α) (VII), dα/dt=A 1exp(-E a1/RT)+A 2exp(-E a2/RT)α(1-α) (IX)]导出了计算(dT/dt) Tb值的9 个表达式. 提出了从不同恒速升温速率(β)条件下的差示扫描量热(DSC)曲线数据计算/确定EMs自催化分解反应的动力学参数和自催化分解转向热爆炸时的(dT/dt) Tb的方法. 由DSC曲线数据的分析得到了用于计算(dT/dt) Tb值的β→0 时的onset 温度(T e0),热爆炸临界温度(T b)和相应于T b时的转化率(α b). 分别用线性最小二乘法和信赖域方法得到方程(I)和(VI)及方程(II)-(V)和方程(VII)-(IX)中的自催化分解反应动力学参数. 用上述基础数据得到了EMs的(dT/dt) Tb值. 结果表明: (1) 在非等温DSC条件下硝化棉(NC, 13.54% N)分解反应可用表观经验级数自催化反应速率方程dα/dt=10 15.82exp(-170020/RT)(1-α) 1.11+10 15.82exp(-157140/RT)α 1.51(1-α) 2.51描述; (2) NC (13.54% N)自催化分解转向热爆炸时的(dT/dt) Tb值为0.103 K·s -1. 相似文献
11.
In the non-isothermal kinetic equation, the temperature integral from 0 to T
0 never equals to zero, so a deviation of activation energy is introduced when the term is neglected. We propose a new evaluation
method on Ozawa Equation. The results show that neglecting this term in Ozawa Equation leads to large activation energy errors,
when small absolute values of Δ x = x − x
0( x = E/ RT). The deviation of the activation energy is less than 0.55% when |Δ x| > 5, but may exceed 10% if |Δ x| < 2. The application of this method on the dehydration of CaC 2O 4· H 2O shows that the theoretical error was close to the actual error. 相似文献
12.
The integral methods, which are obtained from the various approximations for the temperature integral, have been extensively
used in the non-isothermal kinetic analysis. In order to obtain the precision of the integral methods for the determination
of the activation energy, several authors have calculated the relative errors of the activation energy obtained from the integral
methods. However, in their calculations, the temperature integral at the starting temperature was neglected. In this work,
we have performed a systematic analysis of the precision of the activation energy calculated by the integral methods without
doing any simplifications.
The results have shown that the relative error involved in the activation energy determined from the integral methods depends
on two dimensionless quantities: the normalized temperature θ= T/ T
0, and the dimensionless activation energy x
0= E/ RT
0 (where E is the activation energy, T is the temperature, T
0 is the starting temperature, R is the gas constant). 相似文献
13.
The peak temperature ( T
p) and different temperature (Δ T) are the basic information in the differential thermal analysis (DTA). Considering the kinetic relation and the heat equilibrium
in DTA, a correctional differential kinetic equation (containing T
p and Δ T parameter) is proposed. In the dehydration reaction of CaC 2O 4·H 2O, the activation energy calculated from the new equation showed some smaller than that from Kissinger equation, but some
bigger than that from Piloyan equation. 相似文献
14.
Thermogravimetric measurements of weight loss accompanying the pyrolysis of four pitches have been made over a range of linear heating rates. For three of the samples, the data at each heating rate could be described by an integral and a differential method of analysis, assuming a simple order function for f(α), with the result that the apparent activation energy increased with heating rate. The data for all four samples could also be satisfactorily described by the Ozawa or Friedman multiple heating rate methods, and these resulted in apparent activation energies ( Ea) which increased with the value of β at which they were determined. It is suggested that this tendency for the apparent activation energy to increase, as the temperature is raised, is due to a change in the relative importance of the different reactions which lead to weight loss in this system. The apparent kinetic parameters all fall on a common compensation plot which is used to explain the relative magnitude of Ea values from Ozawa and Doyle methods of analysis. The higher values of Ea from Friedman than from Ozawa analyses are also explained. 相似文献
15.
The integral methods are extensively used for the kinetic analysis of solid‐state reactions. As the Arrhenius integral function [ p( x)] does not have an exact analytical solution, different approximated equations have been proposed in the literature for performing the kinetic analysis of experimental integral data. Since the first approximation of Van Krevelen, a large number of equations have been proposed with the objective of increasing the precision in the determination of the Arrhenius integral, as checked from the standard deviation of the approximated function with regard to the real exact value of the integral. However, the main application of these equations is the determination of the kinetic parameters, in particular activation energies, and not the computation of the Arrhenius integral. A systematic analysis of the errors involved in the determination of the activation energy from these integral methods is still missing. A comparative study of the precision of the activation energy as a function of x and T computed from the different integral methods has been carried out. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 658–666, 2005 相似文献
16.
Combustion of brick-shaped carbonaceous materials
(carbon deposits from coke oven, coke and electrographite) was carried out
in thermobalance in static air. Analysis of kinetics of the process was carried
out using both classical (Arrhenius law) and newer (three-parametric equation)
methods. In classical approach two types of kinetic equations were used in
calculations: differential and integral. The results obtained show that, independently
on kinetic variables (α – conversion degree or m
– mass of sample) used in differential equations, kinetics of combustion
of brick-shaped carbonaceous materials is characterized by only one pair of
Arrhenius coefficients: activation energy ( E)
and pre-exponential constant ( A). At the
same time the integral equation demonstrates distinction in relation to methods
based on differential equations, generating higher activation energies and
separate isokinetic effect (IE). Parallel IE shows that kinetic analysis has
to encompass activation energy in connection to second coefficient, pre-exponential
constant A, depending on assumptions made
for kinetic equations. On the other hand three-parametric equation allows
describing kinetic of combustion in alternative way using only one experimental
value – initial temperature in form of point of initial oxidation (PIO)
– and also offers new methods of interpretation of the process. 相似文献
17.
Non-isothermal curing reactions of three different multifunctional epoxy resin systems were investigated by differential scanning calorimetry. The Kissinger equation was applied to calculate the apparent activation energy, and the Levenberg–Marquardt algorithm was used to fit the curing kinetic data. It was observed that the two-parameter model was in good match with the curing kinetics. In addition, dynamic mechanical thermal analysis was used to obtain the glass transition temperature ( T g). Furthermore, the thermal stabilities of the systems were studied by thermogravimetric (TG) analysis, the integral procedure decomposition temperature and temperature index T s were used to characterize the thermal stability. Finally, the gelation time was measured by plate–knife method of a home-made device, and the relationship between gelation time and temperature was established, according to which the pultrusion process parameters were predicted. 相似文献
18.
The study of crystallization kinetics of amorphous alloys has been a matter of great interest for material researchers for past few decades, since it provides information about the kinetic parameters i.e., activation energy of crystallization and the frequency factor. These kinetic parameters can be calculated by model-free isoconversional methods. Isoconversional methods allow calculating the activation energy as a function of degree of conversion, α. Hence, these methods provide accurate results for multistep processes like crystallization. Model-free methods are categorized as linear and non-linear isoconversional methods. Linear methods are further classified as linear differential and linear integral isoconversional methods. In present work, we have used these isoconversional methods to study the effect of non-linear heating rate, employed by modulated differential scanning calorimetry (MDSC), on the non-isothermal crystallization kinetics of Ti 20Zr 20Cu 60 metallic glass. For Ti 20Zr 20Cu 60, MDSC curves clearly indicate a two-step crystallization process. Both crystallization peaks were studied based on the modified expressions for isoconversional methods by non-linear heating rate. The term corresponding to non-linearity comes out to be ( A T ω/2 β) 2. The effect of non-linear heating rate on measurement of kinetic parameters by isoconversional methods is studied. The activation energy of crystallization is calculated for Ti 20Zr 20Cu 60 metallic glass for various degrees of conversion by linear integral isoconversional methods i.e., Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose, and also with Friedman method which is a linear differential isoconversional method. 相似文献
19.
The thermal behavior and kinetic analysis of ammonium uranyl carbonate decomposition has been studied in inert gas, O2, and 90%Ar–10%H2 atmospheres under non-isothermal conditions. The results showed a dependence on specific surface area with the decomposition temperature of ammonium uranyl tri-carbonate (AUC). Specific surface area increases and reaches a maximum between 300 and 400 °C and decreases at T > 400 °C. The reaction paths of AUC decomposition under the three atmospheres were proposed. The integral methods Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) were used for the kinetic analysis. The activation energy averages are 58.01 and 56.19 kJ/mol by KAS and FWO methods, respectively. 相似文献
20.
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
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