Thermodynamics of enzyme-catalyzed esterifications: II. Levulinic acid esterification with short-chain alcohols

Abstract

Levulinic acid was esterified with methanol, ethanol, and 1-butanol with the final goal to predict the maximum yield of these equilibrium-limited reactions as function of medium composition. In a first step, standard reaction data (standard Gibbs energy of reaction Δ g ) were determined from experimental formation properties. Unexpectedly, these Δ g values strongly deviated from data obtained with classical group contribution methods that are typically used if experimental standard data is not available. In a second step, reaction equilibrium concentrations obtained from esterification catalyzed by Novozym 435 at 323.15 K were measured, and the corresponding activity coefficients of the reacting agents were predicted with perturbed-chain statistical associating fluid theory (PC-SAFT). The so-obtained thermodynamic activities were used to determine Δ g at 323.15 K. These results could be used to cross-validate Δ g from experimental formation data. In a third step, reaction-equilibrium experiments showed that equilibrium position of the reactions under consideration depends strongly on the concentration of water and on the ratio of levulinic acid: alcohol in the initial reaction mixtures. The maximum yield of the esters was calculated using Δ g data from this work and activity coefficients of the reacting agents predicted with PC-SAFT for varying feed composition of the reaction mixtures. The use of the new Δ g data combined with PC-SAFT allowed good agreement to the measured yields, while predictions based on Δ g values obtained with group contribution methods showed high deviations to experimental yields.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

“…Levulinic acid was esterified with 1-butanol, ethanol, and methanol catalyzed by N435. 291 In another paper, n-butyl levulinate was synthesized by esterification using Lipozyme RM-IM, Lipozyme TL-IM, and N435 in both a stirred tank batch reactor and a continuous flow packed bed tubular microreactor. 292 N435 was the best catalyst (yields of 85%).…”

Microwave‐mediated noncatalytic synthesis of ethyl levulinate: A green process for fuel additive production

“…Because of environmental concerns, the development of a green process for chemical production has increasingly attracted considerable attention . In recent years, the enzyme‐catalyzed process has been used as a substitute for the chemical‐catalyzed process for the esterification of levulinic acid . Enzyme‐catalyzed esterification has more advantages than the conventional process in terms of the selectivity of enzymes toward the substrate and mild reaction conditions .…”

“…19 In recent years, the enzyme-catalyzed process has been used as a substitute for the chemical-catalyzed process for the esterification of levulinic acid. 20,21 Enzyme-catalyzed esterification has more advantages than the conventional process in terms of the selectivity of enzymes toward the substrate and mild reaction conditions. 20,22 In addition, this process is an ecofriendly process for levulinate ester production.…”

“…20,21 Enzyme-catalyzed esterification has more advantages than the conventional process in terms of the selectivity of enzymes toward the substrate and mild reaction conditions. 20,22 In addition, this process is an ecofriendly process for levulinate ester production. 22 Nevertheless, enzymes are expensive, thus limiting their industrial application.…”

“…Supercritical carbon dioxide and supercritical methanol have been used in the noncatalytic oleic acid esterification. 26 Although this process obtains a high ester yield (90%), it requires a high temperature (553-593 K) and pressure (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25), which raises safety concerns. 26 Therefore, an urgent need exists for another efficient method of developing esterification.…”