Renewable platform chemicals: Evaluation of thermochemical data of alkyl lactates with complementary experimental and computational methods

The standard molar enthalpies of vaporisation of alkyl lactates were derived from the vapour pressure temperature dependences measured by the transpiration method. Thermodynamic data on vaporisation processes available in the literature were collected, evaluated, and combined with own experimental results. Combustion experiments were performed on the highly pure ethyl lactate. We have evaluated and recommended the set of vaporisation and formation enthalpies of alkyl lactates at 298.15 K as the reliable benchmark properties for further thermochemical calculations. Gas phase molar enthalpies of formation of alkyl lactates calculated by the high-level quantum-chemical method G4 were in an excellent agreement with the recommended experimental data. The esterification of lactic acid with alcohols was considered as the model reaction for an industrial processing of biomass conversion to fuels and useful platform chemicals. The high-level quantum chemical calculations have been successfully applied for estimation of reaction enthalpies and the true thermodynamic equilibrium constants in the gas and in the liquid phase. Results of this study could help to reduce the experimental efforts for the assessment of feasibility of the chemical processes of utilization of renewable feedstocks.