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 could not be predicted by thermodynamic models. Thus, 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 the relating reaction kinetics to proton activity. ePC-SAFT advanced model parameters were only fitted to reaction-independent phase equilibrium data, but the key reaction properties were determined by one experimental kinetic curve for a set of temperatures, yielding the reaction enthalpy at standard state dH0=11.48 kJ/mol, activation energy EA=30.28kJ/mol and the intrinsic reaction rate constant k=0.011 s-1 at 323 K, which is independent of catalyst concentration. The new model allows predicting the effects of catalyst, solvent and reactant ratio on LA esterification