Esterification of levulinic acid with 1-butene over acidic ion-exchange resins: Operating conditions and thermodynamic study

Abstract

This project is part of the study of the synthesis of butyl levulinates. Butyl levulinates have a number of properties that make them attractive for inclusion in liquid fuel formulations for both diesel and gasoline. In particular, sec-butyl levulinate is known to improve the anti-knock quality of gasoline. Furthermore, the proposed synthesis route is the esterification of levulinic acid with an olefin, 1-butene. This route, unlike the more traditional routes that employ an alcohol as an esterifier, is not so limited by the extent of secondary reactions. Levulinic acid is a platform compound, derived from lignocellulose and therefore part of what are known as renewable resources based on inedible biomass. In turn, the use of low value-added olefinic streams, such as C4 streams containing linear butenes, which are often burned in refineries, would make it possible to revalue a non-renewable resource and reduce the resulting environmental impact. A mi familia y amigos por todo el apoyo y cariño que me han demostrado siempre. Al Dr. Javier Tejero y a la Dra. Montserrat Iborra por toda la ayuda y dedicación que me han brindado. Gracias a ellos me he sentido acompañada durante todo el proceso de realización del trabajo. Y al Dr. Roger Bringué y al Dr. Jordi Hug Badía por la ayuda proporcionada durante mis primeros días con la instalación. Thus, given the current European legislative framework, which on the one hand requires a minimum of 10% vol. of biofuels by 2020 and on the other hand allows products with a partially renewable origin, such as sec-butyl levulinate, to be counted as biofuels, it is of interest in the short and medium term to study the production of this type of compound. Therefore, in view of the potential industrial implementation of this process, one of the key aspects is the selection of the optimal catalyst, and the other is the determination of the thermodynamics of the reaction. In this sense, the use of ion exchange resins is proposed because they allow high yields to be obtained at relatively low operating temperatures and because they are a type of catalyst that is significantly cheaper than other alternatives in the sector. Of the different commercial options for ion exchange resins available, previous work concluded that Amberlyst 15 appears to be the one that maximizes the production of the desired compound. This catalyst has been used to perform the thermodynamic study of the reaction. The value of the equilibrium constant has been obtained at four different temperatures (90-120 ºC). Due to the high value of the equilibrium constant, it has been considered that the equilibrium is mainly displaced towards the products. The values of the equilibrium constant of SBL formation at different temperatures show that the reaction is exothermic. The value of the standard reaction enthalpy has been estimated.