Etherification of furfuryl alcohol to butyl levulinate, an oxygenate of second generation

Abstract

Governments have established ambitious targets to replace an important fraction of fossil fuels with renewable sources within next 20 years. The EU directives of the Quality & Composition of the fuels expect that the oxygen content of automobile fuels has to be at least 15% at 2020. Consequently, the reformulation of gasoline and diesel oil is needed. Recently, alkyl levulinates, which are bio-based chemicals, have been proposed as gasoline and diesel additives. Butyl levulinate (BL) is an oxygenate of second generation that can be used as diesel additive because it improves the lubricity, conductivity and cold flow properties of the diesel fuel into which it is blended and leads to cleaner combustion processes with fewer smoke or NOx emissions. It can be synthetized from furfuryl alcohol (FA) through acid-catalyzed alcoholysis. Several authors presented efficient catalytic strategies of the reaction using solid acid catalysts. However, the catalysis by means of acid ion exchange resins has been barely investigated. The experiments performed in this work prove that ion exchange resins can be used in the etherification of FA with butanol to obtain BL at 100ºC. The reaction has two steps: conversion of FA to an intermediate which was always complete within 4h and the conversion of the intermediate to butyl levulinate which was more complex. The most relevant byproducts were oligomeric substances indicating that polymerization of FA also took place. The catalyst with the best performance regarding selectivity and mole production was Amberlyst 39 with 67% of selectivity. Besides, it has been found that there is an optimal between accessibility of the active sites of the resin and their acid capacity. The influence of temperature was studied and the selectivity to BL decreased with temperatures lower than 100ºC. Finally, the initial molar ratio effect was also investigated and it was found that selectivity to BL dropped with the increase in initial FA concentration implying that the reaction of polymerization was promoted.