Biomass transformation to biofuels: determination of thermodynamics properties of reaction and selection of optimal catalyst for the esterification of levulinic acid with 1-butene

Abstract

The present project is related to the study of butyl levulinates syntheses, which are products of great interest that, among other applications, can be used as fuel additives for both diesel and gasoline, due to some of their properties. More specifically, the present work is focused on the synthesis of sec-butyl levulinate (SBL), which has been identified as an effective antiknocking agent for gasoline formulations. SBL is considered a biofuel because it is produced from levulinic acid (LA), which is a renewable source of biomass—since it is a platform molecule originated from lignocellulose—, and 1-butene, a low value-added olefin. SBL synthesis pathway proposed in this work is esterification of LA with 1-butene (1B) over an acidic ion-exchange resin as the catalyst. A more traditional, hence more studied, approach to carry out this synthesis is the esterification of LA with 1-butanol, which also leads to water formation and is affected by side reactions in a greater extension than the proposed pathway using an olefin as the esterifying agent. Prior to implementing the studied synthesis at industrial scale, optimal operation conditions, best catalyst, and thermodynamics of the reaction need to be determined. Previous studies concluded that temperatures between 80 and 100 ºC, and 1B excess were the most favorable conditions, and that the optimal catalyst was the ion-exchange resins Amberlyst-15, due to the high yield towards SBL achieved and low extension of side reactions. Therefore, the aim of the present work is to experimentally determine the equilibrium constants of the reaction in the temperature range 90-120 ºC and to determine the thermodynamic properties thereof. Determined values of enthalpy and entropy changes of reaction have been compared to theoretical values, and different estimation methods have been employed