Kinetic Modeling of scCO2-Assisted Levulinic Acid Esterification with Ethanol Using Amberlyst-15 as a Catalyst in a Batch Reactor

Ethyl levulinate has shown great potential as a green fuel additive for gasoline, diesel, and biodiesel. One alternative for its synthesis is the direct heterogeneously catalyzed esterification of levulinic acid with ethanol. Most of the catalytic processes already reported for this system, however, rely on large residence times to deliver appreciable levulinic acid conversions. This work presents experimental and modeling results on the esterification kinetics of levulinic acid with ethanol assisted by supercritical carbon dioxide (scCO2) and catalyzed by Amberlyst-15 in a fixed-volume batch reactor. We explore different molar ratios, catalyst amounts, temperatures, and scCO2 loads. The presented reaction scheme leads to near-equilibrium levulinic acid conversions after less than 60 min at most of the evaluated conditions. To represent the phase-behavior of CO2 + reactants and products, the Peng–Robinson equation of state with a quadratic mixing rule was used. We found that, at most of the experimental conditions, the reaction takes place in a two-phase system due to scCO2; thus, a v-T flash algorithm was coupled to the kinetic model. The proposed kinetic modeling is one of the first attempts to simulate scCO2-assisted reactions in heterogeneous catalytic systems in which the phase partition inside the reactor vessel is considered.