Imed Ben Talouba - Academia.edu (original) (raw)

Papers by Imed Ben Talouba

MATEC Web of Conferences

The kinetics of vegetable oil epoxidation in the presence of different families of surfactants wa... more The kinetics of vegetable oil epoxidation in the presence of different families of surfactants was conducted in an RC1 calorimetric reactor, to explore the micellar effect on the overall rate and kinetic parameters of the reaction. The reaction time was reduced by 2 to 3 hours compared to that obtained in the absence of micelles. A kinetic model is proposed whose parameters are estimated using a method based on the reconstruction of the thermal power profile released by the synthesis. The activation energy of the epoxidation reaction is 44.08 kJ. Safety parameters (MTSR, MTT, TD24) are also determined to study the possibility and severity of thermal runaway.

Journal of Thermal Analysis and Calorimetry

International audienceThis article explores the possibility to determine thermokinetic parameters... more International audienceThis 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 so...

HAL (Le Centre pour la Communication Scientifique Directe), Aug 25, 2018

International audienceAmong polymerization techniques, conventional radical polymerization in sol... more International audienceAmong polymerization techniques, conventional radical polymerization in solution is widely used. Polymerization is composed at least of three main steps known as initiation, propagation and termination [1]. However, undesired reactions, named as chain transfer reaction can cause the formation of polymers with undesirable properties (large Chain length distribution) [2]. To solve this drawback, Living radical polymerization is a promising solution. A Chain Transfer Agent (CTA) is added to the mixture for limiting the irreversible termination reactions [3]. Among Living polymerization strategies, Reversible Addition-Fragmentation Chain Transfer (RAFT) is based on reversible exchange of end group function between a dormant and an active macro radical. This technique may be potentially applied to any polymerizable monomers using operating conditions close to the ones used in conventional radical polymerization[2]. Kinetic parameters of each individual step of the polymerization reaction, in particular propagation constant (kp) can give valuable information in order to optimize the properties of the final polymer (chain lenght distribution, Molar Weight). The knowledge of these kinetic parameters is also essential to evaluate heat released by these reactions, enabling to design a cooling system to reduce thermal runaway risk of reactor. Indeed the reactions of polymerization are implied in industrial accident according to statistics [4]. Most of kinetic studies met in literature are carried out up to low reaction extent, although industrial process are run up to higher extent. Pulsed laser polymerization coupled to size-exclusion chromatography (PLP-SEC) [5] or electron spin resonance (ESR) [6] enable to investigate radical polymerization kinetic with non-stationary conditions. Both techniques can determine kp. Other techniques such as FTIR spectroscopy and calorimetric measurements [7] are also used and are based on the kinetic consumption of monomer. The latter give a global kinetic constant of polymerization reaction (Kpoly) using quasisteady state assumption measurement. These techniques do not allow a quantitative analysis and cannot separate the three different main steps of radical polymerization. In opposition to classical polymerization kinetic studies, the determination of thermokinetic parameters with a calorimetric method using a reaction calorimeter RC1–RTCal allows having operating conditions close to industrial processes and reaching a high reaction extent [4]. This method consists in comparing thermal power profiles measured during experiments with profiles calculated by means of differential equations representing instantaneous mass and energy balances of a mass and energy models. Thus, kinetic parameters of each individual step can be estimated through an inverse method [4]. This present work focuses on the determination of kinetics parameters of RAFT polymerization in solution of dodecyl methacrylate monomers (DDMA) with a calorimetric method using a reaction calorimeter RC1–RTCal. Polymerization is initiated with liquid monofunctional organic peroxide Tert-Butylperoxy 2-ethylhexyl carbonate (TBEC). Anisole is chosen as a solvent according to the fact that Anisole dissolves monomer and the produced polymer and it is also inert with regard to the formed radicals. The reagent 2-Cyano-2-propyl dodecyl trithiocarbonate is selected as CTA because it reacts with methacrylated monomers [3]. The reaction is led under Argon atmosphere as Oxygen is a powerful polymerization inhibitor. The power profile released by the reaction is measured by means of a RC1–RT Cal reaction calorimeter from Mettler. The kinetic parameters of each steps of RAFT polymerization will be estimated using the inverse method, described above

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Chemical Papers, 2020

The kinetics of RAFT polymerization of a dodecyl methacrylate controlled by a trithiocarbonate as... more 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...

La connaissance de la cinetique chimique est primordiale pour la securite des procedes. Parmi les... more La connaissance de la cinetique chimique est primordiale pour la securite des procedes. Parmi les reactions les plus utilisees industriellement, la polymerisation radicalaire occasionne le plus grand nombre d’emballements thermiques dans l’industrie chimique. L’utilisation d’un solvant dans la reaction de polymerisation permet non seulement de disposer d'un tampon thermique mais egalement de controler la viscosite de la masse reactionnelle. Dans cette etude, la cinetique de la polymerisation radicalaire du methacrylate de butyle (BMA) en solution a ete etudiee a differentes temperatures pour deux concentrations en monomere. Quatre solvants ont ete utilises. La nature du solvant influence la cinetique de la polymerisation et doit etre prise en compte pour l’ecriture d’un modele fiable du comportement thermique du milieu reactionnel. Les parametres cinetiques du modele global de polymerisation (modele etat quasi-stationnaire) et du modele faisant appel aux etapes individuelles (am...

Thermochimica Acta, 2020

This study investigates the possibility to use reaction calorimetry to estimate thermokinetic par... more 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.

Thermochimica Acta, 2019

 Nitration of biodiesel in reaction calorimetric to produce a bio-additive.  Chemical and therm... more  Nitration of biodiesel in reaction calorimetric to produce a bio-additive.  Chemical and thermal characterization of the bio-additive used as a cetane number improver.  The heat released by the nitration reaction varies according to the synthesis temperature.  Nitrated biodiesel catalyzes the decomposition of mixed acid  The MTSR is higher than the temperature of decomposition of sulfo-nitric acid.

Journal of Thermal Analysis and Calorimetry, 2017

This article explores the possibility to determine thermokinetic parameters with a calorimetric m... more 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 genetic algorithm estimates individual kinetic parameters of the three steps of the model (initiation, propagation, termination). Kinetic parameters values are compared to literature.

Http Www Theses Fr, 2008

Ce travail concerne la caracterisation des reactions de synthese exothermiques se deroulant en mi... more Ce travail concerne la caracterisation des reactions de synthese exothermiques se deroulant en milieu heterogene liquide-liquide et dont les produits sont des hydrotropes : ils ont la propriete de s’adsorber a l’interface formee par les deux phases. Cette adsorption est accompagnee de modification de la tension interfaciale. L’evolution de cette propriete au cours de la reaction est susceptible de modifier la cinetique de transfert de matiere et indirectement le comportement thermique du milieu reactionnel. Pour illustrer ce type de reaction, l’hydrolyse alcaline d'un ester, le benzoate de methyle, a ete choisie. Outre l’hydrotrope, cette reaction produit un cosolvant (alcool). A l’aide de profils de puissance thermique degagee par le milieu reactionnel et obtenu au moyen d’un reacteur calorimetrique RC1 de Mettler, nous avons montre que ce type de reaction presente un comportement auto accelere suivi d’une phase de deceleration. Il s’agit dans ces travaux d’estimer les parametres cinetiques chimique (constante cinetique k) et de transfert de matiere (coefficient de transfert, aire interfaciale et solubilite de l’ester) ainsi que leur type d’evolution au fur et a mesure de l’avancement de la reaction chimique. Pour mener cette estimation, une methode basee sur la reconstruction de profils de puissance a l’aide d’un modele base sur les ecritures de bilans instantanes d’energie et de matiere a ete adoptee. Deux etudes distinctes quantifiant les effets des produits (l’hydrotrope et le cosolvant) de la reaction, l’une sur la cinetique chimique et l’autre sur celle de transfert de matiere, ont permis de reveler que la modification de la vitesse de transformation chimique est liee principalement a competition entre ces deux cinetiques. Les resultats de l’estimation ont ete presentes sous la forme de correlations reliant ces parametres a la concentration en hydrotrope produit par la reaction.

Thermochimica Acta, 2014

ABSTRACT The thermal decomposition reaction of 1,1-di(tert-butylperoxy)cyclohexane (BPCH) was stu... more ABSTRACT 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.

Journal of Loss Prevention in the Process Industries, 2011

The thermal stability of organic peroxides (cumene hydroperoxide 80 wt% and dicumyl peroxide) was... more 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.

Journal of Chemical & Engineering Data, 2012

Excess molar enthalpies were measured using a Mettler-Toledo RC1 calorimetric reactor at 298 K an... more 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 ethanol (production of acetic acid and ethyl acetate). A novel formula for the excess molar enthalpies of the quaternary system as a function of the molar composition has been developed. It is mainly based on a Margules-type equation which illustrates the quaternary excess enthalpies by taking into consideration the contributions from the corresponding binary and ternary systems. With no solvent present in the reaction system, the thermal behavior may significantly vary with the extent of the reaction taking place. The evolutions of the partial excess enthalpy on the calculation of both the heat of mixing during reaction and the reaction enthalpy were tabulated for various extents of the chemical reaction.

Industrial & Engineering Chemistry Research, 2011

The alkaline hydrolysis of methyl benzoate exhibits autoacceleration kinetics when carried out un... more 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 parameters (overall mass transfer coefficient, interfacial area, ester solubility) during the production of potassium benzoate (hydrotrope). The chemical kinetic (constant rate of alkaline hydrolysis reaction) is very little affected by the reaction products. The quantification of mass flux between phases is solved using double-film model and chemical reaction rate r is expressed as a simple law of the second order. The parameters estimation of mass transfer with reaction has been conducted using thermal power obtained by means of a calorimetric reactor RC1 from Mettler. A Setschenow's type correlation representing the ester solubility and a polynomial form of overall mass transfer coefficient vs the instantaneous concentration of hydrotrope were proposed.

Chemical Engineering Science, 2007

The alkaline hydrolysis of aromatic esters exhibits auto-accelerated kinetics when performed unde... more The alkaline hydrolysis of aromatic esters exhibits auto-accelerated kinetics when performed under two phase conditions. This autoacceleration 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.

Chemical Engineering and Processing: Process Intensification, 2008

An experimental study of an exothermic reaction is carried out in a heterogeneous liquid-liquid r... more 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 TM 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.

Thermochimica Acta, 2017

Decomposition TBEC in solvents takes place with a transfer reaction evidenced by DSC and GC/MS. ... more Decomposition TBEC in solvents takes place with a transfer reaction evidenced by DSC and GC/MS.  The transfer reaction has an enthalpy 10 times lower than the main reaction  The decomposition of TBEC in solvents is modeled by two parallel chemical reactions  The TD24 estimated by DSC is close to that determined experimentally with the ARC.  The TD24 values depend on the nature of the solvent using with peroxide.