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The kinetics of RAFT polymerization of a dodecyl methacrylate controlled by a trithiocarbonate as a chain transfer agent (CTA) are studied by measuring the thermal profile in an RC1-RTCal reaction calorimeter. Contrary to classical methods such as electron spin resonance spectroscopy, the equilibrium constants related to the addition and fragmentation steps are estimated for a high degree of polymerization. The estimation method consists of a comparison between the measured thermal profiles and those built from models reflecting the instantaneous balances of mass and energy. The influence of the concentration of the transfer agent on the characteristics of the polymer (molar mass and dispersity) was also studied at different reaction temperatures. An increase in the concentration of CTA decreases the viscosity of the medium due to a more homogeneous distribution of the small sizes of the polymers. The influence of reaction temperature on the characteristics of polymers is reduced in the presence of CTA.

International audience; This article explores the possibility to determine thermokinetic parameters with a calorimetric method using a reaction calorimeter RC1–RTCal. This method was illustrated with a radical solution polymerization. In opposition to classical polymerization kinetic studies (PLP, DSC), operating conditions are near industrial processes and kinetic parameters are estimated up to high reaction extent. The method consists in comparing thermal power profiles measured during experiments with profiles calculated by means of a model. A minimization method based on a geneticalgorithm estimates individual kinetic parameters of the three steps of the model (initiation, propagation, termination). Kinetic parameters values are compared to literature.; Cet article explore la possibilité de déterminer les paramètres thermocinétiques par une méthode calorimétrique à l’aide d’un calorimètre de réaction RC1 – RTCal. Cette méthode a été illustrée par une polymérisation radicalaire en solution. Contrairement aux études cinétiques de polymérisation classiques (PLP, DSC), les conditions de fonctionnement sont proches des processus industriels et les paramètres cinétiques sont estimés jusqu’à un avancement de réaction élevé. La méthode consiste à comparer les profils de puissance thermique mesurés lors d’expériences avec des profils calculés à l’aide d’un modèle. Une méthode de minimisation basée sur un algorithme génétique estime les paramètres cinétiques individuels des trois étapes du modèle (initiation, propagation, terminaison). Les valeurs des paramètres cinétiques sont comparées à la littérature.

The aim of this study was to synthesize a substitute to the 2-Ethyl Hexyl Nitrate (EHN) by nitrating a biodiesel. EHN is commonly used to improve the auto-ignition properties of diesel fuels. The biodiesel was obtained by trans-esterification of canola oil. The nitration reaction was carried out in a reaction calorimetry RC1 with semi-batch mode to study its exothermic behavior. Mixed sulfuric/nitric acid was used as nitrating agent. The impact of the synthesis temperature on the thermal behavior and on the reaction medium composition was investigated. The final product was analyzed by using several analytical techniques such as iodine number, infrared spectrometry, GC–MS and mass spectrometry. This analytical study combined with the results of thermal stability study in DSC, allowed to highlight that chemical transformations play an important role on the thermal reaction behavior and on the Maximum Temperature of the Synthesis Reaction (MTSR). In addition to the mixed acid decomposition, the synthesis at high temperature involves the production of nitrated products: methyl-8-nitro oleate, methyl-10-nitrate stearate, methyl-10-nitrate-9-nitrostearate. Also, the Cooperative Fuel Research (CFR) engine was used to analyze the cetane number of diesel fuel mixed with our additive according to the ASTM D613 standard. The results showed an increase in cetane number of 3.2 points.

This study investigates the possibility to use reaction calorimetry to estimate thermokinetic parameters of an industrial reaction. The synthesis chosen in this study is the radical polymerization of butyl methacrylate in different organic solvents. The kinetic parameters estimation method is based on the comparison of experimental thermal power profiles released during polymerization and measured using a reaction calorimeter RC1-RTCal with calculated power profiles by means of a simplified model. Individual kinetic parameters of the three main steps (initiation, propagation, termination) were estimated using a minimization method based on a genetic algorithm. Contrary to classical methods, in this paper the three kinetic parameters are estimated simultaneously and at high conversion. The measurement of physical properties, average molecular mass, polydispersity index and viscosity, made it possible to understand the effect of the solvents nature on individual kinetic rate constants. Estimated results are in good consistency with those encountered in the literature obtained by classical methods.

International audience; The thermal decomposition reaction of tert-butyl (2-ethylhexyl) monoperoxy carbonate (TBEC) was studied insolution with different solvents (anisole, xylene and ethylbenzene) and alone. The kinetics of each system wasexplored by DSC measurements in isothermal and non-isothermal conditions. Analysis of heat flow profiles released in the isothermal mode combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer allowed to propose a chemical decomposition model. An empirical nth order rate equation was used to describe the decomposition of neat TBEC. In pure solvent the mechanism was modeled by two parallel reactions. The first one followed an empirical nth order rate equation. The second one was modeled by a transfer reaction of the radical to the solvent. An adiabatic calorimeter was used to identify the effects of solvents on important reactive hazards such as onset temperature, pressure hazard and the Time to maximum rate (TMRad) or temperature at which TMRad is 24 h (TD24). The last parameter was compared with that estimated by DSC study. The kinetic parameters estimation was achieved using a mixed estimation method where a genetic algorithm is combined with a locally convergent method.; La réaction de décomposition thermique du monoperoxy carbonate de tert-butyle (2-éthylhexyle) (TBEC) a été étudiée en solution avec différents solvants (anisole, xylène et éthylbenzène) et seul. La cinétique de chaque système a été explorée par des mesures DSC dans des conditions isothermes et non isothermes. L’analyse des profils de flux thermiques libérés en mode isotherme, combinée à l’analyse des produits de décomposition par un chromatographe en phase gazeuse / spectromètre de masse, a permis de proposer un modèle de décomposition chimique. Une équation empirique du nième ordre a été utilisée pour décrire la décomposition de TBEC pur. Dans les solvants purs, le mécanisme a été modélisé par deux réactions parallèles. La première suivait une équation empirique du nième ordre. La seconde a été modélisée par une réaction de transfert du radical dans le solvant. Un calorimètre adiabatique a été utilisé pour identifier les effets des solvants sur des dangers réactifs importants tels que la température initiale, le risque de pression et le temps jusqu’à la vitesse maximale (TMRad) ou la température à laquelle TMRad est à 24 h (TD24). Le dernier paramètre a été comparé à celui estimé par l’étude DSC. L’estimation des paramètres cinétiques a été réalisée à l’aide d’une méthode d’estimation mixte associant un algorithme génétique à une méthode localement convergente.

International audience; This paper deals with an analytical method to assess the maximum temperature value along a tubular chemical reactor at steady state. This reactor is provided with a jacket in which a counter current cooling liquid flows. The thermal behavior of the chemical reactor is calculated with the McCormack numerical method. Comparison of the exothermic reaction generated flux with the removed flux from the separating wall leads to a two-part reactor subdivision. In the first part, the reactor behaves as an adiabatic reactor followed by a zone in which the flux removed from the wall is not negligible and remains constant. In the second part, the reactor behaves like a simple heat exchanger without internal energy source. Analytical integration of mass and energy balance equations in each subsystem was used to determine the analytical expression of maximum temperature.

This study deals with an observer built for distributed parameter systems described by nonlinear representations. This observer was applied to a tubular chemical reactor in order to estimate the maximum temperature of the reactant mixture and its position in stationary and transient regimes. This estimation uses a Luenberger observer, while MacCormack's numerical method was used for resolution of the partial differential equations. Furthermore, to take into account the nonlinearity of the system, the gain of this estimator was proposed as a function of the position along the chemical reactor. This observer requires the values of both concentration and temperature at the inlet but only of temperature at the outlet. The convergence and robustness of this estimator were experimentally tested with initialization and modeling errors.

The thermal stability of organic peroxides (cumene hydroperoxide 80 wt% and dicumyl peroxide) was studied by means of calorimetric measurement (DSC, TA Q1000) in an isotherm mode and a dynamic mode. Analysis of power profiles released in the isothermal mode was combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer (GC/MS) to determine the reaction mechanisms corresponding to each of the two reactions. In this work, a methodology for estimating kinetic parameters was based on the comparison of the power profile (dynamic mode) given by the model to that obtained experimentally by changing the parameters values. Parameter estimation is achieved using the mixed estimation method where a genetic algorithm is combined with a locally convergent method.

The alkaline hydrolysis of methyl benzoate exhibits autoacceleration kinetics when carried out under biphasic conditions. This autoacceleration is mainly linked to modification of mass transfer par...

An experimental study of an exothermic reaction is carried out in a heterogeneous liquid–liquid reaction mixture, producing simultaneously a surfactant and a cosolvent. The mass transfer kinetic is influenced by the presence of these products, as reaction advances. The global rate of the chemical transformation is thus accelerated. The chosen reaction is the saponification of methyl benzoate with a soda solution at 2 M. The reaction is carried out in a Mettler™ RC1 calorimetric reactor. Thermal power profiles released by reaction mixture are used to estimate energetic and chemical kinetic parameters, as well as those linked with mass transfer. Mass balance uses a chemical kinetic law of second order. The quantification of mass transfer between phases is solved using double-film model.

The alkaline hydrolysis of aromatic esters exhibits auto-accelerated kinetics when performed under two phase conditions. This auto-acceleration behavior is linked to reaction products effects (surfactant and co-solvent) on mass transfer kinetics. The co-solvent increases the equilibrium concentration of organic compounds in aqueous solution, while the surfactant modifies the mass transfer coefficient and interfacial area. In this research work, the selected reaction is the alkaline hydrolysis of methyl benzoate carried out in a calorimetric reactor Mettler RC1 in isothermal semi-batch mode. The parameters estimation of mass transfer and chemical kinetics has been conducted using thermal power profile. Two functions—giving the evolution during reaction of the mass transfer coefficient and the equilibrium concentration—are proposed accordingly to surfactant and co-solvent concentrations.

In this paper, we present a method for detecting faults that can appear in some parts of a chemical plant. This method is based on statistical information generated by the Extended Kalman Filter (EKF) technique and is designed to reveal any drift from the normal behavior of the process. Originally developed for linear systems, our contribution to this method consists in extending it to unsteady state nonlinear systems, such as stirred reactors in the presence of exothermic chemical reactions. We examined the abnormal behavior of a chemical reactor due to one fault in its control parameters. An abrupt variation of cooling flow rate has been studied experimentally. The objective of this experimental study is to detect the presence of such faults online, and to pinpoint the moment one occurs.

International audience; The thermal decomposition reaction of 1,1-di(tert-butylperoxy)cyclohexane (BPCH) was studied in pure solvents (anisole, xylene and ethylbenzene) and alone. The kinetics of each system was explored by means of microcalorimetric measurements (DSC) in isothermal and non-isothermal conditions. Analysis of heat flow profiles released in the isothermal mode combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer allowed to propose a chemical decomposition model. An empirical nth order rate equation was used to describe the decomposition of BPCH alone. In pure solvent, the mechanism was modeled by two parallel reactions. The first one followed an empirical nth order rate equation. The second one was modeled by a transfer reaction of the radical to the solvent. The kinetic parameters estimation was achieved using a mixed estimation method where a genetic algorithm is combined with a locally convergent method.; La décomposition thermique du 1,1-di(tert-butylperoxy)cyclohexane (BPCH) a été étudiée dans différents solvants (anisole, xylène et éthylbenzène) et seul. La cinétique de chaque système a été étudiée à l’aide de mesures microcalorimétriques (DSC) en conditions isothermes et non isothermes. Une analyse des profils de flux de chaleur libérés en mode isothermique combinés à l'analyse des composés par un chromatographe en phase gazeuse / spectromètre de masse a permis de proposer un modèle de décomposition chimique. Une équation empirique du nième ordre a été utilisée pour décrire la décomposition de BPCH seul. Dans les solvants purs, le mécanisme a été modélisé par deux réactions parallèles. La première suivait une équation empirique du nième ordre. La seconde a été modélisée par une réaction de transfert du radical vers le solvant. L’estimation des paramètres cinétiques a été réalisée à l’aide d’une méthode d’estimation mixte dans laquelle un algorithme génétique est combiné avec une méthode localement convergente.

A rotating film pertraction of phenol from its dilute aqueous solutions and copper from ammoniacal dilute leach solutions are presented. Mathematical models are developed to describe the batch pertraction processes. Using experimental results and models, the partial mass transfer coefficients and the kinetic constants were evaluated.

International audience; A hybrid estimation method is proposed to estimate simultaneously the kinetic and energetic parameters of chemical models. This method combines a genetic algorithm with a local convergence method, the former generating initialisation points for the latter. The method is applied to a real complex chemical system : the saponification of ethyl acetate at a concentration of 1 mol.L-1. The reaction is carried out in a calorimetric reactor which determines experimental profiles of power delivered or absorbed by the reaction mass. A model, based on mass and energy balances in the reaction mass, including the kinetic and energetic parameters of the reaction, allows to calculate the power profile. The comparison between the experimental and calculated profiles gives the criterion to minimise. The parameters of the model are successfully determined. The hybrid method determines more efficiently and more rapidly the solution of the problem than a set of several estimations with a local convergence method.

Equipment faults in industrial chemical reactors lead to variations in product quality. Due to the highly energetic potential of the reaction mass, they can in addition cause runaways or major incidents. The methodology for detecting process anomalies in a chemical reactor, is based on a parametric estimation-prediction of the reaction mixture. The recursive least square method with forgetting factor has been retained to appreciate the evolution of parameters in real time. Thus allowing us, to point out a criterion of decision based on relative prediction error between two successive vector parameters. In this paper, we consider only the stirred jacketed chemical reactor which is largely use in pharmaceutical fine chemistry. Two incidents linked to the hydrodynamic cited by Etchelles (Etchelles., 1994) as main causes of reported incidents are studied: a change in the fluid flow regime in the jacket and the immediate stop of the agitator. In each case, a dynamic simulation model, based on energetic balances, is established to represent the most accurate reactor thermal behaviour.

The unsteady state temperature of the reactive mixture along a tubular reactor presents a maximum value resulting from the exothermicity of the chemical reaction.The knowledge of the maximum temperature, (position and value) is an important indicator for safety and quality of reactors in which a highly exothermic reaction takes place. This paper deals with experimental and theoretical estimation and localization of this maximum temperature along a chemical tubular reactor at unsteady state. This reactor is equipped with a jacket in which the refrigerating fluid flows in counter current configuration.The reaction undertaken in the inner tube of the reactor is oxidation of sodium thiosulfate by hydrogen peroxide.The unsteady state is described from the resolution of the model equations, obtained from mass and energy balances, with the numerical method of McCormack.The influences of hydrodynamic, thermal and chemical parameters on the value and position of the maximum temperature are studied.

Excess molar enthalpies were measured using a Mettler-Toledo RC1 calorimetric reactor at 298 K and 0.1 MPa for the quaternary system which may occur during the hydrolysis of acetic anhydride with e...

In this paper, we present a method for detecting faults that can appear in some parts of a chemical plant. This method is based on statistical information generated by the Extended Kalman Filter (EKF) and is designed to reveal any drift from the normal behavior of the process. Although this method was originally developed for linear systems, our contribution consists in extending it to unsteady state nonlinear systems such as stirred reactors in the presence of exothermic chemical reactions. We examined the abnormal behavior of a chemical reactor due to three different faults in its control parameters. Each fault is caused by an abrupt variation in the value of one of the following parameters: the cooling temperature, the stirring rate of the reaction mass, and the feeding flow rate of the reactant. The objective of this experimental study is to detect the presence of such faults on-line and to pinpoint the moment each occurs, as well as to determine the delay in detection with respect to the decision thr...

Solvent-free reactions are an interesting alternative for the chemical industry, which seeks to improve productivity. However, the physical and chemical properties of the reaction mixture evolve continuously during the reaction from pure reagents to final products. This evolution can lead to a modification of kinetic and energetic parameters. As an illustration, we chose to study the esterification of acetic anhydride by methanol, catalyzed by sulfuric acid and using a calorimetric reactor. A slowing down of the reaction rate was observed by recording the rate of energy released by the reaction for each successive addition of acetic anhydride. The kinetic and energetic parameters of the model were estimated thanks to a hybrid method, using a genetic algorithm together with a locally convergent method.

A global method is proposed for estimating the kinetic and energetic parameters of chemical reactions taking place in the continuous phase of a heterogeneous liquid/liquid system. This method, based on energy and mass balances, uses the thermal power freed or absorbed by the reaction mass. It is only applicable to systems with sufficient thermal effects. Knowledge of the mass flow exchanged between the dispersed and continuous phases is needed to establish the mass balance. It is determined thanks to a model based on the double film theory. The model was applied to the saponification of pure ethyl acetate in an aqueous reaction mass. It was possible to determine simultaneously the velocity constant and the reaction enthalpy, as well as the apparent overall mass transfer constant.