关于ABS树脂热失重数据的计算

在解析TG曲线时,常用的方法有积分法和微分法,但反应级数需要通过预先假定和尝试确定.本文以ABS树脂热解反应为对象,采用三次样条插值函数求得热解反应速率,利用二元线性回归经一次计算,同时求得ABS树脂热解反应表观活化能E,视频因子A以及反应级数n,并把所得结果与积分法和微分法作了比较,确定了各自方法所适用的转化率区间.本文还考察了不同升温速率对热解动力学参数的影响.     

配合物[Fe(CTS)2]·5SO4·7H2O的热分解动力学

研究了壳聚糖对Fe2+的吸附行为,并进行了条件优化,得到了较为理想的合成产物.通过红外光谱和紫外光谱进行了表征,进而用化学分析、元素分析确定了配合物的组成,并利用TG-DSC分析,采用常用的22种机理函数,对非等温动力学数据进行了线性回归拟合处理,求得了配合物主要分解阶段热动力学最可机理函数和动力学参数(E和A).     

配合物[Fe(CTS)2]·5SO4·7H2O的热分解动力学

研究了壳聚糖对Fe2+的吸附行为,并进行了条件优化,得到了较为理想的合成产物.通过红外光谱和紫外光谱进行了表征,进而用化学分析、元素分析确定了配合物的组成,并利用TG-DSC分析,采用常用的22种机理函数,对非等温动力学数据进行了线性回归拟合处理,求得了配合物主要分解阶段热动力学最可机理函数和动力学参数(E和A).     

配合物[Fe(CTS)_2]·SO_4·7H_2O的热分解动力学

研究了壳聚糖对Fe2 + 的吸附行为 ,并进行了条件优化 ,得到了较为理想的合成产物。通过红外光谱和紫外光谱进行了表征 ,进而用化学分析、元素分析确定了配合物的组成 ,并利用TG DSC分析 ,采用常用的 2 2种机理函数 ,对非等温动力学数据进行了线性回归拟合处理 ,求得了配合物主要分解阶段热动力学最可机理函数和动力学参数 (E和A)。     

化学反应动力学研究法──自函数回归法及其应用

由完全非线性函数经变换得到自函数递推方程．根据回归分析理论，建立了一种化学反应动力学研究法──自函数回归法．应用该法在25℃水溶液中研究了乙酸乙酯和了酸乙酯的皂化反应的动力学常数．     

水杨酸钴非等温热分解动力学研究

用热分析(TG/DTG)、X射线衍射(XRD)技术研究了固态物质水杨酸钴在空气中热分解的过程。热分析结果表明,水杨酸钴在空气中分两步分解,其失重率与理论计算失重率相吻合;XRD结果表明,水杨酸钴分解的终产物为Co3O4。用Friedman法和Flynn-Wall-Ozawa(FWO)法求取了分解过程的活化能E,并用多元线性回归和多元非线性回归法给出了可能的机理函数,由这些方法得到的动力学数据相互比较吻合。     

化学反应动力学研究法

由完全非线性函数ｆ（ｔ）＝Ａ＋Ｂｅ＾－ｋ１ｔ＋Ｃｅ＾－ｋ２ｔ经变换得到自函数递推方程，根据回归分析理论，建立了一种化学反应动力学研究法－－自函数回归法，应用该法在２５℃水溶液中研究了乙酸乙酯和丁酸乙酯的皂化反应的动力学常数。     

速差动力学因子分析法测定重稀土混合物

因子分析是解决多变量问题的一种数学方法,在化学中已应用于成分分析,但在速差动力学分析中常的应用未见报道。速差动力学分析中常用的曲线拟合法需先知道混合物的组成,并用纯组分求出动力学参数,而因子分析可不必事先知道组分数及求动力学参数。本文应用因子分析法测定重稀土的二元及三元混合物,得到较好的结果。     

用FRKS状态方程预测三元系超额体积

利用改进的立方状态方程－ＦＲＫＳ方程，并以二元互作用函数代替单一数值的二元互作用参数关联二元系的超额体积，得到二元参数，在不引入任何三元参数的情况下，直接用组分二元系作用函数的引入预测三元系的超额体积，对十二个三元系及其组分二元系的计算结果表明，二元互作用函数的引入明显提高了二元超额体积的拟合精度，从而使状态方程法能精确地预测三元系的超额体积。     

顺丁烯二酸酐-癸二酸二丁酯二元体系等温气液平衡

利用改进的沸点仪测定了顺酐-癸二酸二丁酯二元体系在413.15, 433.15和453.15 K下的等温气液平衡数据以及纯癸二酸二丁酯和顺酐的饱和蒸气压数据. 通过与文献值对比, 验证了此方法的可靠性. 同时, 将实验数据回归得到了纯癸二酸二丁酯和顺酐的Antoine常数. 利用NRTL方程进行了气液平衡数据的关联推算, 得到了顺酐-癸二酸二丁酯二元体系的NRTL模型参数. 利用UNIFAC基团贡献法对实验数据进行了预测, 其结果与实验值及运用NRTL方程拟合的结果吻合较好.     

Kinetic analysis of thermogravimetric data obtained under linear temperature programming—a method based on calculations of the temperature integral by interpolation

A new technique, called interpolation method, with general application in the kinetic analysis of processes studied by thermogravimetry (TG) under linear temperature programming is developed. It is based on the linear relationship, with slope 1, between log g() and log I(γ, θ) for the appropriate kinetic function, where I(γ, θ) is the normalized temperature integral, θ the normalized temperature (θ=T/T₀) and γ a dimensionless activation energy (γ=E/RT₀). Values of log I(γ, θ) are calculated by linear interpolations in a pre-built table. This method can easily be programmed and implemented in a personal computer, where the results (kinetic parameters and quality of regressions for the kinetic functions considered) are typically obtained in a very short time. The method is validated by analyzing different simulated thermogravimetric curves and comparing the results with those determined with some classic methods taken from the literature. In addition, the results are compared with the values obtained by a similar method, also developed and explained in this paper, which involves the evaluation of all the values of the temperature integral by numerical integration, therefore, demanding a much larger calculation time. The interpolation method is found to be more accurate than other published methods, particularly in the case of thermogravimetric curves corresponding to processes with low activation energies. The results obtained are always similar to those determined by the integration method, which is taken as reference. Application of the technique to experimental data for various types of reactions shows that the results are in agreement with the published parameters and kinetic laws.     

3,7-二硝基亚氨基-2,4-二氮杂双环[3,3,0]辛烷的放热分解反应动力学

The kinetic parameters of the exothermic decomposition reaction of the title compound in a temperature-programmed mode have been studied by means of DSC. The DSC data obtained are fitted to the integral, differential and exothermic rate equations by 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 (Ea), pre-exponential factor (A) and reaction order (n) will be obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential form and the values of Ea and A of this reaction are (1-α)0.44, 230.4 kJ/mol and 1018.16 s-1, respectively. With the help of the heating rate and obtained kinelic parameters, the kinetic equation of the exothermic decomposition reaction process of the title compound is proposed. The critical temperature of thermal explosion of the compound is 302.6℃. The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal change rule of the title compound.     

Two-dimensional and three-dimensional fitting of enzyme kinetic data with the kalman filter

The availability of instrumentation which is capable of collecting multidimensional data has put increased demands on the data-processing methods utilized to obtain information about reaction kinetics. An enzyme-catalyzed reaction, the hydrolysis of p-nitrophenyl phosphate to p-nitrophenol, is examined so that various data-processing methods and data-collection formats can be examined and compared. The extended Kalman filter is used to obtain rate constants and values for the initial substrate concentration for three-dimensional data, and for two-dimensional kinetically perturbed data. In addition, non-linear least-squares regression with the simplex algorithm, and linear least-squares regression methods are used to analyze absorbance/time curves for this reaction. These results are compared to the results from a two-point kinetic method, and the accuracy and precision of each of the methods is evaluated. It is found that the methods based on the Kalman filter yielded results which were equivalent to or better than the results obtained from the other approaches.     

Theoretical Consideration of the Grafting of Polymer Chains onto Fullerene C60

Summary: For the first time, the kinetics and statistics of the formation of polymer stars by grafting linear macromolecules onto the fullerene C₆₀ are considered. Two kinetic models are put forward providing an explanation for some important experimentally observed peculiarities of these macromolecular reactions. The comparison of the results found from the solution of the kinetic equations and those obtained by Monte Carlo simulations demonstrates their good agreement. Due to the minimal number of the parameters involved, the theoretical approach proposed is rather convenient for the treatment of experimental data.

     

Approaching the direct exponential curve resolution algorithm from a maximum likelihood perspective

The implementation of maximum likelihood parallel factor analysis (MLPARAFAC) in conjunction with the direct exponential curve resolution algorithm (DECRA) is described. DECRA takes advantage of the intrinsic exponential structure of some bilinear data sets to produce trilinear data by a simple shifting scheme, but this manipulation generates an error structure that is not optimally handled by traditional three-way chemometrics methods such as TLD and PARAFAC. In this work, the effects of these violations are studied using simulated and experimental data used in conjunction with the well-established TLD and PARAFAC. The results obtained by both methods are compared with the results obtained by MLPARAFAC, which is a method designed to optimally accomodate a variety of measurement error structures. The impact on the estimates of different parameters linked to the data sets and the DECRA method is investigated using simulated data. The results indicate that PARAFAC produces estimates of much poorer quality than TLD and MLPARAFAC. Also, it was found that the quality TLD estimates was comparable or only marginally poorer than the MLPARAFAC estimates. A number of commonly used algorithms were also compared to MLPARAFAC using two sets of published experimental data from kinetic studies. The MLPARAFAC estimates of rate constants were more precise than the other methods examined.     

Kinetic analysis of the complex process of poly(vinyl alcohol) pyrolysis using a new coupled peak deconvolution method

A peak deconvolution procedure used for the analysis of data corresponding to simultaneous overlapping processes begins with separation of individual processes using functions such as Gaussian, Lorentzian, Weibull, and Fraser–Suzuki (FS) followed by application of kinetic analysis methods to the separated peaks. We propose a coupled peak deconvolution procedure to link the parameters of the FS functions of similar peaks in two DTG curves obtained at different linear heating rates, so that the coordinates of each peak can be obtained in a constrained manner. The proposed technique is a kinetic deconvolution method rather than a pure mathematical deconvolution technique. To analyze individual peaks in our study, the non-parametric kinetic and Freidman’s isoconversional methods have been applied to determine kinetic triplet of each process. This technique has been tested with both simulated and experimental data. Using this technique, the effects of molecular weight and degree of hydrolysis of polyvinyl alcohol (PVA) samples on reaction mechanism and activation energy of thermal degradation were studied. The presence of acetate group in the PVA samples causes thermal stability, decreases the rate of main reactions, and increases the activation energy. The results of this study may help tailor heat-resistant materials with proper choice of polymer characteristics.     

Evaluation of kinetic parameters from thermogravimetric curves: Part I. Combined numerical method

A new method is proposed to evaluate kinetic parameters from thermogravimetric traces. The method consists of two steps, α, T and dα/dT values are first employed to estimate kinetic parameters by linear least squares fitting, using the five types of mechanism for solid phase reactions suggested by ?esták. From the different sets of parameters thus obtained, the most probable mechanism type is decided. The resultant parameters for the chosen type of mechanism may further be improved by differential correction method, if necessary, using the more accurate data of α and T. The proposed method was tested with artificial data and the data for the thermal dehydration of gypsum by ?esták et al. The results were very satisfactory.     

Kinetics of dehydroxylation and evaluation of the crystallinity of kaolinite

This study presents results on the kinetics of kaolinite dehydroxylation. The accuracy of various methods of determining the values for the kinetic parameters and their sensitivity in detecting the mechanism of reaction is investigated. In particular, the differential order of reaction method of Baker, the general method of Achar et al., the integral method of Boy and Bohme, and the method of Coats and Redfern as modified by Fong and Chen are considered.

Kaolinites from well-known sources are used to study the influence of crystallinity on the values of kinetic parameters. The statistical significance of the various mathematical methods for the assessment of the data obtained from non-isothermal thermogravimetry is determined by comparison with experimental and theoretical data using a computer programme developed for this purpose. The study demonstrates that the kinetic parameters can be used to quantify the degree of crystallinity of kaolinite and also confirms other findings that the dehydroxylation of kaolinite is a second-order reaction.