Equilibrium thermodynamics of the liquid phase esterification of levulinic acid with octanol over an ion exchange resin

Abstract

The objective of this work is to characterize the thermodynamics of the synthesis reaction of octyl levulinate from levulinic acid and 1-octanol in liquid phase. In the current context of depletion of the traditional resources of raw materials and fuels as well as the fight against climate change, numerous efforts are being carried out to develop material production processes from renewable resources. This is the case of octyl levulinate, a compound that, due to its physical and chemical characteristics such as its density, volatility and viscosity, has a high potential as a substitute for lubricant bases traditionally obtained from crude oil. Octyl levulinate is considered a biomolecule as it is synthesized from levulinic acid, one of the 12 biomassderived molecules with the greatest potential according to U.S. Department of Energy, and 1-octanol, which can also be obtained through bioprocesses. As a previous step to the design of processes for its synthesis, the thermodynamic properties of this esterification need to be determined. Despite the existence of several kinetic studies of the esterification of levulinic acid with 1-octanol, the thermodynamic constant of this reaction is experimentally determined for the first time in this work. Its value at 80, 100 and 120 ºC is compared with those computed via estimation methods. Likewise, the enthalpy change and the entropy change of the reaction are experimentally determined and compared with theoretically estimated values. On the other hand, an experimental purification method of the synthesized octyl levulinate based on the combination of washing the reaction medium with water followed by vacuum rectification is described. Finally, the value of the isobaric heat capacity of octyl levulinate is experimentally determined for the first time at different temperatures, and these values are compared with those obtained via a theoretical estimation method