Article Dans Une Revue Industrial and engineering chemistry research Année : 2025

Predicting Proton Activity and Acid Dissociation Equilibria in Mixed-Solvent Systems, and Their Impact on Esterification Kinetics of Levulinic Acid

Résumé

This study presents a novel thermodynamicmodeling approach for predicting the reaction kinetics ofesterification reactions. The system studied in detail was levulinicacid esterification by various alcohols, using sulfuric acid as ahomogeneous catalyst at reaction temperatures between 323 and353 K at atmospheric pressure. The effects of temperature, solvent,and cosolvent on the kinetics and equilibrium of LA esterificationwere found to be significant. The novel modeling approachdeveloped in this work introduces absolute proton activity intoreaction formalism by focusing on a thermodynamic description ofthe catalyst effects on reaction kinetics. That required accuratemodeling of proton activities, Gibbs energies of solvation, and aciddissociation equilibria in the mixed aqueous−organic reactionsystem that changes composition with reaction progress. In this work, the electrolyte equation of state ePC-SAFT was applied topredict absolute proton activities in mixed solvent systems. The ePC-SAFT parameters were adjusted by literature-based data onproton Gibbs energies of solvation and on acid dissociation equilibria. The new approach allowed very good accuracy in calculatingproton Gibbs energies of solvation, acid dissociation equilibria, and absolute proton activity in mixed-solvent systems. It couldquantitatively explain the disadvantageous effect of water on kinetics, despite acid dissociation in water solvent is strong while protonactivity is very low. Ultimately, this allowed predicting the influence of catalyst, solvent and of cosolvent addition on the kinetics andthe equilibrium of the esterification, demonstrating that the cosolvent γ-valerolactone had minimal effect on the kinetics while watersignificantly decreased the reaction rate and sulfuric acid addition accelerated the reaction depending on sulfuric acid concentration.To conclude, this approach allows for a reduction in experimental effort by reliably predicting the influence of the key reactionconditions on kinetics and equilibria of chemical reactions.1. INTRODUCTIONThe esterification of carboxylic acids is fundamental towardsynthesis of daily life chemical products. It is most commonlyperformed in a single liquid phase, and sulfuric acid (H2SO4) istypically used as a homogeneous catalyst. Among thecarboxylic acids, levulinic acid (LA) is a substance of highinterest since LA and its esters, the alkyl levulinates (AL), areimportant platform molecules1 derived from the hydrolysis oralcoholysis of cellulose and hemicellulose.2 ALs serve asoxygenate additives and diesel blend components in the fuelindustry, enhancing fuel quality and reducing emissions.3,4Tian et al.5 showed that methyl levulinates and ethyllevulinates possess superior antiknock properties comparedto Euro95 gasoline. The synthesis of LA and ALs fromlignocellulosic biomass includes complex chemical simulta-neous reactions in which compounds such as water and alcoholact as both reactants and solvents.Since reaction equilibria and kinetics for reactions (such asLA esterification to ALs) depend strongly on temperature,solvent composition, catalyst, and concentration, a model isdesired to capture these effects and decrease the experimentaleffort. Thus, generalized thermodynamic concepts have beendeveloped. Kiviranta-Pää kkö nen6 found that modeling kineticsof an etherification, including the activity coefficients of thereacting agents, allowed for a more accurate description ofexperimental data over a wide range of conditions, which wasnot possible for a similar model that neglected these activitycoefficients. Lemberg and Sadowski7 showed that the equationof state PC-SAFT allowed the prediction of the solvent effecton reaction kinetics. Since then, the concept of activitycoefficients of reactants for describing the kinetics of liquid

Domaines

Fichier non déposé

Dates et versions

hal-04986610 , version 1 (11-03-2025)

Identifiants

Citer

Marcel Klinksiek, Sindi Baco, Sébastien Leveneur, Julien Legros, Christoph Held. Predicting Proton Activity and Acid Dissociation Equilibria in Mixed-Solvent Systems, and Their Impact on Esterification Kinetics of Levulinic Acid. Industrial and engineering chemistry research, 2025, pp.6188-6202. ⟨10.1021/acs.iecr.5c00115⟩. ⟨hal-04986610⟩
70 Consultations
0 Téléchargements

Altmetric

Partager

  • More