sec-Butyl levulinate production by esterification of levulinic acid with 1-butene over acidic ion-exchange resins: a screening study

Abstract

The need to reduce petroleum dependence and its emissions, a tough environmental legislation and the obligation to achieve the 10% in volume use of additives from renewable resources by 2020 in Europe forces the industry to focus on obtaining green-fuels to reduce pollution. Acid hydrolysis of cellulosic materials produce carbohydrates C5 and C6 whose transformation results in a series of compounds called platform chemicals, which are the first step to the synthesis of numerous compounds of potential interest in the chemical industry. One of them is levulinic acid (LA). This acid can be obtained with semi-commercial processes such as Biofine, and the literature proposes it as a starting point for obtaining fine chemicals and additives compounds suitable in fuels reformulation with bio-compounds. Moreover, the raw material proceeds from inedible biomass which means that a possible ethic issue is avoided. Butyl levulinates, a levulinic acid derivative, have excellent properties as fuel additives because has good cetane index close to commercial fuels, improves good circulation at low temperatures and reduces the exhaust emissions. In particularly, sec-butyl levulinate is a good octane improver This work is focused on the liquid phase esterification reaction of levulinic acid with 1-butene (1B) to obtain sec-butyl levulinate (SBL) by acid catalysis. SBL can also be synthesize by reacting LA with 2-butanol instead of 1B, but the use of the olefin is desirable since it avoids the formation of unwanted products, such as polymerization compounds, ethers and water, which are produce when the alcohol is used. Also, is a refinery stream currently without commercial value, so ester production would allow its upgrading. To carry out the reaction, it is proposed to work with acidic ion-exchange resins as catalysts, which are economic catalysts able to work at low temperatures, with a flexible morphology and with a high adaptability to the reaction medium. The main goal of the work is to find an active resin in terms of conversion and selectivity towards ester, which minimizes the oligomers formation as by-products at temperatures below 140 ºC.Experiments conducted show that the use of acid resins in levulinic acid esterification with 1-butene to obtain sec-butyl levulinate can result in with high conversions and selectivity. Macroreticulated resins have shown the highest catalytic activity, Amberlyst 15 (A15) showing a higher rate of sec-butyl levulinate generation. Therefore, it can be concluded that resins with more DVB, higher acid capacity and lower gel phase are favoured in this reaction medium.