Synthesis of hydrated furans: Analysis of the Prins reaction mechanism

Mechanistic analysis of hydrogenated furan synthesis by the Prins reaction was carried out using mathematical modeling. The direct and inverse chemical kinetic problems are solved for the rate constants of all elementary steps. A probable mechanism is derived from the obtained quantitative kinetic parameters and the kinetic patterns of the reaction. These include kinetic curves from the concentration changes of all species in the reaction.     

Non-equilibrium thermodynamics and kinetic theory of gas mixtures in the presence of interfaces

A broad range of the boundary value problems of the kinetic theory of gases and gas mixtures is considered based on kinetic theory and non-equilibrium thermodynamics. The interrelation of the kinetic theory and non-equilibrium thermodynamics is discussed. The balance equations at the interface are obtained for the case of the boundary layers with peculiar properties. Procedures for deriving the boundary conditions for slightly rarefied gas mixtures are outlined. The problems of calculating slip coefficients are discussed. The specificity of the kinetic effects in the boundary conditions is shown. A set of general relations related to gas mixture flows in capillaries is deduced. The possibility of non-equilibrium kinetic effects in the form of a paradoxical distribution of non-equilibrium temperature is shown. Methods of non-equilibrium thermodynamics are used to obtain the phenomenological equations describing the thermophoresis and diffusiophoresis of particles and cross phenomena. The growth and evaporation of droplets is considered based on kinetic theory and non-equilibrium thermodynamics.     

Kinetic analysis of the mechanism of plasminogen activation by streptokinase

A kinetic study is made of plasminogen activation to plasmin catalyzed by streptokinase. The goal of the present paper is the resolution of the mechanism corresponding to the activation process by a global way, considering the mechanism as a whole and under less restrictive assumptions that those used by other authors. The kinetic equations describing the evolution with time of species involved in the system have been obtained. These equations are valid for both the transient phase and the steady state of the reaction. A kinetic data analysis procedure to evaluate the kinetic parameters, based on the derived kinetic equations has been suggested, for the first time, in the present paper. The validity of the results obtained has been checked by using simulated progress curves of the species involved. Finally, we have demonstrated that the time course equations obtained can be applied directly to different mechanisms of zymogen activation that could be considered to be particular cases of the general studied mechanism.     

Sensitivity analysis of the two kinetic states of the Belousov-Zhabotinsky reaction

A recently published kinetic model of the Belousov-Zhabotinsky reaction was studied by the feature sensitivity analysis of the slow bromide consumption and slow bromide production periods of the relaxing-type oscillatory system. The computed sensitivities allowed us to reveal the kinetic importance of the 17 individual reactions during the two, “kinetically homogeneous” states of the oscillation. Similarities and differences in the relative kinetic importances of the reaction steps were carefully studied when changing the magnitude of the rate constants (high set and low set). Of the 17 reactions examined, the attack of Ce⁴⁺ on malonic acid proved to be an essential step of the mechanism. Using the low set, there emerge more reactions which significantly affect the length of the two kinetic states.     

Addition effect of erbium(III) trifluoromethanesulfonate in the homopolymerization kinetics of a DGEBA resin

Solid bisphenol-A epoxy resin of medium molecular weight was cured using a Lewis acid initiator (erbium(III) trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr). A kinetic study was performed in a differential scanning calorimeter. The complete kinetic triplet was determined (activation energy, pre-exponential factor, and integral function of the degree of conversion) for each system. A kinetic analysis was performed with an integral isoconversional procedure (model-free), and the kinetic model was determined both with the Coats-Redfern method (the obtained isoconversional E value being accepted as the effective activation energy) and through the compensation effect. All the systems followed the same isothermal curing model simulated from non-isothermal ones. The “nucleation and growth” Avrami kinetic model A_3/2 has been proposed as the polymerization kinetic model. The addition of initiator accelerated the reaction having higher influence when low temperatures were applied.     

Kinetic studies on the decomposition of cyano complexes. I. the thermal decomposition of cyanoferrate(II) acids

The formation of HCN from solid iron(II) cyano complex acids is studied by a non-isothermal kinetic method. A derivatograph is used for the measurements and the kinetic parameters are calculated by different methods using the Horowitz—Metzger, Coats—Redfern and Zsako equations. The results are discussed and the kinetic parameters (energy and entropy of activation) are compared with IR and Mössbauer spectroscopic data.     

一种活性磷酸酯的分子内亲核取代反应动力学研究

合成和表征了大环过渡金属配合物NiL(L:高氯酸-5,7,7,12,14,14-六甲基-1,4,8,11-四氮杂环十四烷)。配合物NiL与表面活性剂组成的金属胶束作为模拟水解金属酶用于催化BNPP水解。提出了BNPP催化水解的机理;建立了用于计算动力学常数的动力学模型;计算了相关的动力学和热力学常数。结果表明,这种金属胶束表现出较高的催化活性;BNPP催化水解反应是分子内亲核取代反应;所提出的机理和建立的动力学模型是合理的。     

Kinetic and chemometric studies of the determination of creatinine using the Jaffé reaction. Part I. Kinetics of the reaction: analytical conclusions

A kinetic-spectrophotometric study of the Jaffé reaction was carried out and the kinetic behaviour, calibration step and interfering effect of albumin on creatinine standard solutions were studied. It was concluded that there is a variation in the kinetic behaviour of the system when higher concentrations of creatinine, picrate or sodium hydroxide are tested. The experimental conditions for quantifying creatinine must be chosen so that the kinetic behaviour is the same in the dynamic concentration range. Changes in the absorbance (delta A) versus concentration equations were chosen as the most suitable for calibration graphs. It was also shown that creatinine results will have a proportional bias error if the interfering effect of albumin is not taken into consideration.     

Comparative study on the thermal behavior of two similar triterpenes from birch

A comparative study on the thermal behavior of betuline and betulinic acid was performed using a TG–FTIR hyphenated technique. The comparison was focused on the kinetic of the relevant thermal-induced phenomenon. Using three different data processing strategy, that is, Friedman, Flynn–Wall–Ozawa, and nonparametric kinetic, homogeneous values for the activation energy were obtained, especially by betulinic acid. The advantages of the nonparametric kinetic method were revealed, especially by obtaining the explicit kinetic parameters of the conversion function, without any “a priori” hypothesis.     

The mathematical origins of the kinetic compensation effect: 1. The effect of random experimental errors

The kinetic compensation effect states that there is a linear relationship between Arrhenius parameters ln A and E for a family of related processes. It is a widely observed phenomenon in many areas of science, notably heterogeneous catalysis. This paper explores one of the mathematical, rather than physicochemical, explanations for the compensation effect and for the isokinetic relationship. It is demonstrated, both theoretically and by numerical simulations, that random errors in kinetic data generate an apparent compensation effect (sometimes termed the statistical compensation effect) when the true Arrhenius parameters are constant. Expressions for the gradient of data points on a plot of ln A against E are derived when experimental kinetic data are analysed by linear regression, by non-linear regression and by weighted linear regression. It is shown that the most appropriate analysis technique depends critically on the error structure of the kinetic data. Whenever data points on a plot of ln A against E are in a straight line with a gradient close to 1/RT, then confidence ellipses should be calculated for each data point to investigate whether the apparent compensation effect arises from random errors in the kinetic measurements or has some other origin.     

Kinetic studies on the thermal polymerization of N‐chloroacetyl‐11‐aminoundecanoate potassium salt

A potassium salt of N‐chloroacetyl‐11‐aminoundecanoate was thermally polymerized to obtain the corresponding poly(glycolic acid‐alt‐11‐aminoundecanoic acid). A kinetic study was then performed that was based on isothermal and nonisothermal polymerizations performed in a differential scanning calorimeter. The complete kinetic triplet was determined (the activation energy, pre‐exponential factor, and integral function of the degree of conversion). A kinetic analysis was performed with an integral isoconversional procedure (free model), and the kinetic model was determined both with the Coats–Redfern method (the obtained isoconversional value being accepted as the effective activation energy) and through the compensation effect. The polymerization followed a three‐dimensional growth‐of‐nuclei (Avrami) kinetic mechanism. Isothermal polymerization was simulated with nonisothermal data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1166–1176, 2005     

Functional derivative of the kinetic energy functional for spherically symmetric systems

Ensemble non-interacting kinetic energy functional is constructed for spherically symmetric systems. The differential virial theorem is derived for the ensemble. A first-order differential equation for the functional derivative of the ensemble non-interacting kinetic energy functional and the ensemble Pauli potential is presented. This equation can be solved and a special case of the solution provides the original non-interacting kinetic energy of the density functional theory.     

测定可逆反应动力学参数的一种新方法

提出了测定一级可逆反应速率常数的新方法,用以测定稀土的偶氮胂Ⅲ络合物与CyDTA交换反应的速率常数,并详细讨论了测定速率常数时动力学数据的选取原则。     

The determination of kinetic parameters for the decomposition of complex substances from thermogravimetry data

A procedure for thermogravimetry data processing was suggested. It was based on treatment of a substance as a superposition of fractions, the decomposition of which occurred independently and could be described by first-order kinetics with the corresponding kinetic parameters, that is, activation energy and preexponential factor. The theoretical dependences of weight loss were constructed using exact solutions to kinetic equations. The results obtained by the determination of the kinetic parameters for two coal samples are presented.     

A Kinetic Model for the Acid-Catalyzed Decomposition of Delrin

Abstract

A kinetic model is derived for the acid-catalyzed decomposition of Delrin, an acetal-formaldehyde resin. The kinetic model proposed assumes the hydrolysis of Delrin to form polyformaldehyde and the subsequent decomposition of polyformaldehyde to formaldehyde.     

An alternative Avrami equation to evaluate kinetic parameters of the interaction of Hg(II) with thin chitosan membranes

In this work, thin chitosan membranes were utilized as an adsorbent for the removal of Hg(II) from aqueous solutions. A rise of temperature accelerates the mass transfer of Hg(II) to the membranes, surfaces. The kinetic data did not present a good fitting to the traditional Lagergren adsorption kinetic equations. An alternative Avrami kinetic equation was employed and successfully fitted to the kinetic adsorption quantities. From this new equation, two regions presenting distinct kinectic parameters were found, and the use of the parameter n was also relationed to the determination of the kinetic order. Variations of the adsorption kinetic rate in relation to the time, the initial Hg(II) concentration, and the temperature were also calculated and are discussed.     

A kinetic study of the oxidation of uranium dioxide

Summary A kinetic model for the oxidation of a UO₂ pellet is suggested by considering the mass transfer and the diffusion of oxygen molecules. The kinetic parameters were estimated by a fitting of the experimental data. The activation energies for the chemical reaction and the product layer diffusion were calculated from the kinetic model. The suggested model explains well the oxidation behavior of UO₂.     

Reaction Kinetics of the Hydroperoxide Epoxidation of 1-Octene in the Presence of Mo2B

The kinetics of epoxidation of 1-octene by tert-butyl hydroperoxide in the presence of molybdenum boride (Mo₂B) was studied. The effects of reactant and reaction product concentrations on the process were examined. A kinetic scheme was proposed, and the kinetic parameters of the process were calculated.     

Kinetic models for the chemisorption of organic compounds on oxide surfaces

A kinetic equation for chemisorption on amorphous oxide surfaces is proposed, and activation energies, pre-exponential factors for reactions of various organosilicon compounds with Si, Ti and Al oxide active sites are calculated. Relationships between the kinetic parameters and reagent structure were established.