Activity-based models to predict kinetics of levulinic acid esterification

The solvent is of prime importance in biomass conversion as it influences dissolution, reaction kinetics, catalyst activity and thermodynamic equilibrium of the reaction system. So far, activity-based models were developed to predict kinetics and equilibria, but the influence of the catalyst on kinetics has not been succesfully predicted by thermodynamic models. In this work, the thermodynamic model ePC-SAFT advanced was used to predict the activities of the reactants and of the catalyst at various conditions (temperature, reactant concentrations, γ-valerolactone GVL cosolvent addition, catalyst concentration) for the homogeneously acid-catalyzed esterification of levulinic acid (LA) with ethanol. Different kinetic models were applied, and it was found that the catalyst influence on kinetics could be predicted correctly by simultaneously solving the dissociation equilibrium of H2SO4 catalyst along the reaction coordinate and by relating reaction kinetics to proton activity. ePC-SAFT advanced model parameters were only fitted to reaction-independent phase equilibrium data. The key reaction properties were determined by applying ePC-SAFT advanced to one experimental kinetic curve for a set of temperatures, yielding the reaction enthalpy at standard state urn:x-wiley:14394235:media:cphc202200729:cphc202200729-math-0001 , activation energy urn:x-wiley:14394235:media:cphc202200729:cphc202200729-math-0002 and the intrinsic reaction rate constant k=0.011 s−1 at 323 K, which is independent of catalyst concentration. The new procedure allowed an a-priori identification of the effects of catalyst, solvent and reactant concentration on LA esterification

Kinetic modelling: Regression and validation stages, a compulsory tandem for kinetic model assessment

International audienceThe development of robust and reliable kinetic models is vital to build safe, eco-friendly, and cost-competitive chemical processes. Establishing kinetic models for complex chemical systems such as biomass valorization is cumbersome because the kinetic modeller must test different models and fit several experimental observables (or concentrations). Usually, in chemical reaction engineering, kinetic model assessment is based solely on the regression stage outputs. The implementation of a validation stage can aid in choosing the most reliable kinetic models, essentially in the case of complex chemical systems. We studied the solvolysis of 5-hydroxymethylfurfural (5-HMF) to butyl levulinate (BL) as a model reaction constituting several consecutive and parallel reaction steps. From an existing kinetic model, we created 60 synthetic runs in batch conditions. In the first part, we tested four different models with 5 degrees of noise, and we carried out the modelling on the 60 synthetic runs. In the second part, two types of holdout methods were evaluated. In the last part, cross-validation, namely the k-fold method, was used. We found that the 10-fold method allowed more efficient selection results even when the noise level was high. Besides, k-fold allows for not scarifying experimental runs and selecting the most reliable model

Synthèse catalytique et décomposition des acides peroxycarboliques

The purpose of this thesis was to find a way to produce peroxycarboxylic acid from hydrogen peroxide and carboylic acid in a continuous reactor by using heterogeneous catalysts. In the first step the stability of peroxyde species xas studied by using an online analytic method (Mass spectrometer). One of the main challenge was to find a suitable solid acid catalyst, wich does no decompose the peroxyde species and can catalyze the reaction as sulfuric acid. A continuous fixed bed reactor was built by using caion exchange resins as a catalyst.L'objectif de cette thèse fut de développer un process pour la production d'acide peroxycarbolique à partir du peroxyde d'hydrogène et d'un acide carboxylique dans un réacteur continu. Dans un premier temps, la stabilité des espèces peroxydées fut étudiée en utilisant une méthode d'analyse en direct (spectromètre de masse). Un effort particulier a été apporté pour trouver un catalyseur hétérogène ne provoquant pas la décomposition des espèces peroxydées et ayant une activité catalytique similaire à l'acide sulfurique. Un réacteur en continu en lit fixe a été construit en utilisant des résines échangeuses de cation

Special Issue on “Thermal Safety of Chemical Processes”

International audienceChemistry plays an essential role in our modern society [...

Alternative method to prevent thermal runaway in case of error on operating conditions continuous reactor

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Novel Intensified Alternatives for Purification of Levulinic Acid Recovered from Lignocellulosic Biomass

International audienceThe development of a bio-based economy has its foundations in the development of efficient processes to optimize biomass potential. In this context there are a multitude of molecules that can be either synthetized or recovered from biomass, among those the so-called 12 building-blocks reported by the US Department of Energy. Even if their identification and importance is clearly defined, research efforts concerning the purification or separation of these platform molecules are limited. To fill this gap, different configurations for the purification of levulinic acid recovered from lignocellulosic biomass are examined and compared in this work. In particular, hybrid configurations obtained by the combination of liquid-liquid extraction and distillation have been considered. It was demonstrated how a deep understanding of the subspace including all extraction-assisted simple column distillation configurations represents a fundamental step in the synthesis of different process alternatives. From a separation efficiency and economic standpoint, the proposed intensified liquid-liquid thermally equivalent configuration (LL-TE) and liquid-liquid side stream column configuration (LL-SSC) are promising solutions. Nonetheless, their performances are deeply interrelated to the purity target defined by the designer

Structure–Reactivity: Comparison between the Carbonation of Epoxidized Vegetable Oils and the Corresponding Epoxidized Fatty Acid Methyl Ester

International audienceVegetable oils are renewable biomass that can substitute fossil raw materials for sustainable development. These oils are made of different types of fatty acids (building blocks), which could lead to differing reactivity toward chemical reaction. In order to investigate the correlation between reactivity and structure of vegetable oils, we have compared the reactivity of epoxidized cottonseed oil (ECSO) and its epoxidized fatty acid methyl ester (EFAME) toward carbonation reaction by using the homogeneous catalyst tetrabutylammonium bromide (TBABr). Mass transfer and physicochemical properties were determined and further applied to estimate the intrinsic rate constants during the kinetic modeling stage. It was found that densities for both systems were similar, but the difference in viscosity was important. Mass transfer coefficients were similar for the carbonated species, but the ones of EFAME and FAME were found to be ca. 100 times lower than those of ECSO and CSO. The solubility of CO2 was found to be higher in FAME derivatives than in CSO derivatives. We have found that the rate constant of carbonation of EFAME can be 1.4 times higher than the one of ECSO. A linear relationship between the carbonation rate constant of epoxidized vegetable oil and its fatty acid methyl ester with temperature was found

Thermal risk assessment of vegetable oil epoxidation

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Catalytic Epoxidation Reaction

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