Modeling hydrolysis and esterification kinetics for biofuel processes

We determined the kinetics for ethyl oleate hydrolysis in high-temperature water and for the reverse reaction, oleic acid esterification, in near- and supercritical ethanol. Hydrolysis was clearly autocatalytic. The experimental data, from reactions at 150-300 °C, times from 5 to 1440 min, and with different initial concentrations of reactants and products, were used to estimate thermodynamically and thermochemically consistent Arrhenius parameters for the forward and reverse reactions in an autocatalytic reaction model. The model provided a good correlation of the data and also exhibited the ability to make quantitatively accurate predictions within the parameter space investigated. The model also accurately predicted the experimental trends when extrapolated outside the original parameter space. Sensitivity analysis confirmed that data from both fatty acid esterification and fatty acid ester hydrolysis need to be used together if one desires reliable estimates for all of the Arrhenius parameters in the autocatalytic model.