邻苯二酚与甲代烯丙基氯的醚化反应动力学

呋喃酚（2,3-二氢-2,2-二甲基-7-苯并呋喃酚）是制造杀虫剂呋喃丹（克百威）的重要中间体．呋喃酚的工业生产主要有邻硝基酚法、环已酮法和邻苯二酚法．同其他生产工艺比较,邻苯二酚法具有生产简单、收率高等优点．因此,目前工业上主要采用邻苯二酚法．     

A nonisothermal differential scanning calorimetry study of the curing kinetics of an unsaturated polyester system

Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.     

聚氨酯柔性固化剂/环氧体系固化动力学及机理

通过不同升温速率下示差扫描量热分析(DSC)研究了自制的聚氨酯柔性固化剂ATPU/环氧树脂E-44体系的固化反应动力学及机理。通过Kissinger和Crane方程求解了表观活化能和反应级数等动力学参数,并运用该参数研究了固化反应速率常数、固化反应速率、固化度等的变化规律及影响因素。通过反应级数的研究证明了固化反应为一复杂反应,不同的固化交联反应同时发生,但主要进行的是伯氨基及仲氨基与环氧基之间的反应,该类反应使得体系得以固化。     

In situ determination of aniline polymerization kinetics through near‐infrared spectroscopy

This article describes a method for the determination of kinetic constants in aniline polymerizations performed in the presence of dodecylbenzene sulfonic acid. The procedure was based on the measurement of light absorbances at 668 and 1026 nm. The absorption at 668 nm is related to pernigraniline formation and is ordinarily used for ultraviolet–visible kinetic studies. The absorption at 1026 nm is related to the second overtone of the N? H bonds, which may be used to monitor the aniline consumption along the reaction time. Tzou and Gregory's empirical reaction model was used as a reference for kinetic studies. The best fits were obtained when the kinetic constants were evaluated at 1026 nm because of the lower noise/signal ratio in this spectral region and the smaller sensitivity to the pernigraniline/emeraldine transition during the last stages of the polymerization. The remarkable innovation supplied by this study is the possibility to study aniline polymerizations in situ in realistic reaction conditions, which will allow the use of concentrated monomer solutions, large reaction volumes, efficient cooling conditions, and agitation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A molecular kinetic model incorporating catalyst acidity for hydrocarbon catalytic cracking

This work built a molecular-level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate reaction rates. The n-decane and 1-hexene co-conversion catalytic cracking process was chosen as the studying case. The molecular reaction network was automatically generated using a computer-aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under several reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with kinetic parameters. The built model can calculate the product distribution, gasoline composition, and molecular distribution at different reaction conditions for different catalysts. This sensitive study shows that it will facilitate the model-based optimization of catalysts and reaction conditions according to product demands.     

Heats of reaction and kinetics of a thermoset polyester

The curing reaction of a thermoset polyester was investigated by using the isothermal and dynamic techniques of differential scanning calorimetry (DSC). The heats of reaction (at different curing temperatures) and a kinetic expression of the crosslinking reaction are presented and compared to the results of the previous studies. The proposed kinetic model can be utilized to obtain the rates of heat generation and the extent of cure at different cure temperatures and time. The overall activation energy of the curing reaction was calculated on the basis of experimental data as 17.0 kcal/mole and the overall reaction rate constant as 2.60 × 10⁹ exp (?17,000/RT) min^?1.     

Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry     

Modelling of kinetics and mass transfer in the hydrogenation of xylose over Raney nickel catalyst

This paper discusses the modelling of xylose hydrogenation kinetics over Raney nickel in aqueous solutions, the determination of the hydrogen solubility in the reaction mixture as well as evaluation of mass transfer effects in the reaction system. The hydrogenation experiments were carried out batchwise in an automatic laboratory‐scale reactor. The reactor system operated at a pressure range of 40–70 bar and at temperatures between 80 and 140 °C. The catalyst‐to‐xylose ratio was approximately 5 wt‐% of the xylose weight normally. The reactor contents were analysed off‐line with a high performance liquid chromatograph. Hydrogen solubility in the reaction medium was determined with a gas‐chromatographic system. The solubility was found to remain fairly constant during the hydrogenation. Only a slight increase in the hydrogen solubility was detected as xylose was hydrogenated to xylitol. The overall hydrogen solubility in the reaction mixture was significantly lower than in pure water, as expected. The main hydrogenation product was xylitol, but small amounts of xylulose and arabinitol were detected as by‐products. A semi‐competitive kinetic model, based on hydrogen and xylose adsorption, was developed. The model accounts for the very different areas covered by a hydrogen atom and an organic species on the catalyst surface. The parameters of the kinetic model were determined with non‐linear regression analysis. It turned out that the kinetic model is able to describe the formation of both xylitol and the by‐products. The mass transfer effects in the batch hydrogenation were evaluated by using measured viscosities and estimated diffusion and mass transfer coefficients. A process simulator, utilizing the kinetic and mass transfer effects, was developed to predict the behaviour of industrial reactors. © 1999 Society of Chemical Industry     

低温液相甲醇合成反应动力学模型与参数估计

由低温液相甲醇合成的反应机理出发 ,考虑了均相和多相催化剂的不同作用及不同的吸附方式 ,导出了两步法低温液相甲醇合成的动力学模型 .结合搅拌釜中测得的动力学数据 ,对动力学模型进行了筛选和参数回归 .结果表明氢气为分子吸附 ,反应为双位吸附反应 ,甲醇脱附为反应控制步骤的反应动力学模型能较好地拟合实验数据 .由此得到了低温液相甲醇合成反应动力学模型方程 ,模型满足F检验 ,且参数符合各自的物理意义 .该动力学模型由于是对两步反应综合起来进行动力学分析 ,因而结果可在反应器数学模型中应用     

Pd/C上松香催化歧化反应集总动力学

以松香为原料、改性Pd/C为催化剂、200#油为溶剂及N2为保护气,进行松香催化歧化反应集总动力学的研究。在消除内外扩散影响的条件下,在线跟踪48315～53315 K的反应产物并用毛细管柱气相色谱法测定反应体系组成随时间的变化关系。根据松香歧化反应机理和特点,借鉴集总思想和方法,按结构族组成和动力学相近原则划分该复杂反应体系的集总组分,构建了Pd/C上松香歧化集总反应网络,建立了枞酸型树脂酸、海松酸型树脂酸、氢化枞酸型树脂酸、氢化海松酸型树脂酸和脱氢枞酸五集总动力学模型;采用Levenberg-Marquart法,以Matlab编程和SPSS数理统计软件估算了模型参数,得到枞酸型树脂酸脱氢、加氢,海松酸型树脂酸加氢反应过程的活化能分别为11139 kJ·mol-1、10876 kJ·mol-1、9735 kJ·mol-1,结果表明,所建动力学模型与实验数据吻合良好,并能预测反应在54315 K的集总组分浓度分布。     

Analysis of the heat-release mechanism during thermal stabilization of polyacrylonitrile fiber rope

Results of experimental studies of heat release during heating of polyacrylonitrile (PAN) rope are presented. The heating conditions for PAN rope samples of elemental fiber linear density 0.08, 0.10, and 0.12 tex to 330°C at rates 2, 3.5, and 5 K/min were selected to model thermal stabilization processes in an oxidation furnace. These data were used to determine the kinetic constants in the Arrhenius equation using the method proposed by L. I. Volkova. Experimental heat release in rope as a function of time at various heating rates was used to determine the kinetic reaction constants. Kinetic constants of the generalized reaction were determined for all tested ropes and conditions. A heat-release equation was formulated based on the kinetic constants for each PAN rope sample. The rope mass change as a function of time M(t) expressed in fractions and represented as a second-order polynomial was determined from the rope mass loss at heating rate 3.5 K/min.     

Acetaldehyde dimethylacetal synthesis with Smopex 101 fibres as catalyst/adsorbent

The synthesis of dimethylacetal using acetaldehyde and methanol as raw material in the presence of Smopex 101 fibres as catalyst and adsorbent in batch reactor and in a fixed bed adsorptive reactor, respectively, was studied. In the batch reactor the determination of thermodynamic and reaction kinetics data for acetalization reaction was presented. A kinetic model based on a pseudo-homogeneous rate expression using activities was proposed to describe the experimental kinetic results. The dynamic binary adsorption experiments were carried out in the absence of reaction at 293.15 K in a laboratory scale column. The experimental results of the adsorption of binary non-reactive mixtures are reported and used to obtain multi-component adsorption equilibrium isotherms of Langmuir type. The mathematical model was proposed to describe the adsorptive reactor dynamic behaviour. The experimental results obtained for the reaction and regeneration experiments were compared with the model proposed. Model equations were solved by orthogonal collocation on finite elements (OCFE) implemented by the PDECOL package, using the measured model parameters and was validated for both reaction and regeneration steps.     

Photocatalytic intrinsic reaction kinetics. II: Effects of oxygen concentration on the kinetics of the photocatalytic degradation of dichloroacetic acid

The effect of oxygen on the reaction kinetics of the photocatalytic oxidation of dichloroacetic acid at pH below the titanium dioxide isoelectric point (pH from 5 to 4) was studied. A kinetic scheme based on the direct hole attack to the dichloracetate ion in conjunction with the classical role of oxygen acting as an electron acceptor is proposed. Oxygen also intervenes in a direct addition reaction to one of the intermediate reaction products. Experiments were conducted in a well-mixed, small, flat plate reactor employing Aldrich titanium dioxide as the photocatalyst in the suspension mode and using polychromatic irradiation with energy in the range from 275 to 385 nm in wavelength. A complete mathematical model, including the effect of the absorbed radiation intensities and catalyst concentration was developed. Experimental data agree well with theoretical predictions employing just two kinetic parameters derived from the proposed reaction mechanism.     

八碳芳烃临氢异构化反应动力学模型

针对某实际工业异构化装置,在已开发的八碳芳烃临氢异构化反应网络的基础上,将系统中的八碳环烷烃和八碳链烷烃作为一个集总组分,提出新的六组分异构化反应网络,由此建立了适用于工业生产的八碳芳烃临氢异构化反应动力学模型.考虑结焦对催化剂活性的影响,提出了一种经验形式的催化剂失活函数,能够合理地描述催化剂失活过程.采用四五阶Runge-Kutta法对模型方程进行数值求解,基于多套稳态平衡数据采用差分变尺度优化算法(BFGS)对动力学参数进行估计,进而在不同操作条件下对模型进行验证.结果表明估计值与工业标定值相当吻合,达到了工业应用的模拟精度要求.     

Kinetic study of phenolic resin cure by IR spectroscopy

The cure reaction of a commercial phenolic resin (FRD‐5002, Borden Chimie S.A.) has been studied by IR spectroscopy (Fourier transform IR). A phenomenological approach was used to characterize the kinetic of reaction. Various kinetic models, including homogeneous reactions, diffusion‐controlled reactions, phase boundary movement, and nucleation and growth‐type kinetic, have been tested. Kinetic analyses using integral procedures on isothermal data indicate that the cure reaction data can be described above 140°C using the homogeneous first‐order reaction model. The activation energy has been found to be about 49.6 kJ mol⁻¹. At lower temperature, a diffusive mechanism was active, and the kinetic of reaction was well described by the Jander kinetic model. Because of the simple kinetic control active above 140°C, a mechanistic model for the resol cure at these temperatures has been also proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2703–2715, 1999     

半纤维素稀酸循环喷淋冲滤水解动力学

采用稀酸循环喷淋冲滤（dilute acid cycle spray flow-through,DCF）反应器在温和的条件下水解玉米秸秆半纤维素,分析了半纤维素稀酸水解产物组分,研究不同温度、硫酸浓度和时间对主要产物木糖浓度的影响。探讨了其水解反应机理并以酸催化反应机理为基础,把玉米秸秆半纤维素及其水解产物按化学组成和性质进行集总划分,并对反应网络进行合理简化,提出了一种半纤维素稀酸水解反应的简化集总动力学模型。通过参数估计求取动力学参数,建立集总动力学模型以预测半纤维素主要水解产物。结果表明,喷淋作用加快了半纤维素的连续解聚过程,从而使得木糖得率超过90%,而其降解产物糠醛等较少。得到的模型能较好预测不同条件下主要产物含量。通过改进的Arrhenius方程确定木糖生成和降解的活化能分别为107.1 kJ·mol^-1和102.2 kJ·mol^-1。     

CFCs加氢脱氯合成HFCs反应动力学研究进展

综述了CFCs加氢脱氯合成HFCs反应的催化剂、动力学的研究进展。其中,动力学着重于研究反应历程和反应能量。反应历程主要使用动力学法,也辅助性地运用同位素示踪技术、傅立叶变换红外光谱等方法进行研究。反应能量主要采用原子团加和方法以及密度泛函理论进行估算。     

Simultaneous Isomerization and Etherification of Isoamylenes with Methanol

The effect of feed MeOH/2M1B molar ratio on the initial isomerization and etherification rates of 2‐methyl‐1‐butene (2M1B) was studied in a batch reactor. The initial reaction rates for etherification and isomerization increased when the MeOH/2M1B molar ratio decreased. The ratio of etherification and isomerization rate was 2–3 until at lowest initial MeOH/2M1B molar ratio 0.2, where the isomerization rate increased significantly. At MeOH/2M1B molar ratio 0.2 the isomerization reaction rate was twice as high as the etherification reaction rate. Several kinetic formulations were tested to explain this new data and the data obtained in earlier studies. According to the statistics, a kinetic model based on three active sites gave the best fit, but it was discussed that the basic Langmuir‐Hinshelwood mechanism might be more adequate. An improved fit of the Langmuir‐Hinshelwood model was obtained, when a correction factor describing the acceleration of isomerization rate with the molar fraction of 2M1B was added into the kinetic equations.     

THE “UCKRON-1” TEST PROBLEM FOR REACTION ENGINEERING MODELING†

Testing kinetic models against a “true” and detailed kinetic expression was the aim of the Workshop on Kinetic Model Development at the Denver AIChE Meeting in August, 1983. For this purpose an artificial reaction mechanism was created, based on the known thermodynamics of the methanol synthesis as a framework. The kinetic rate laws, that were derived from this mechanism, were made thermodynamically consistent by achieving agreement between equilibrium constants calculated at various temperatures from the given, real original thermodynamic relationship and those calculated from the detailed reversible kinetic expressions.

Using the artificial kinetics as the "true" one, CSTR experiments were simulated. The results of a statistically designed set of experiments were published after 5% random error was added to the data. Participation was invited for all interested to correlate the data, develop kinetic models and to calculate the performance of the specified reactor.

The results of 19 submitted entries are summarized with the conclusion that the models had more differences than were expected, but their predictive values were not as different as was anticipated, if the extreme high production rates due to thermal runaways are not considered. This in turn points out the necessity to check models experimentally, in pilot plant, not only for predicted optimum, but also for calculated runaway conditions. Models which did not capture the true character of this reaction failed to predict the onset of runaway reactions.