Study of thermostable resins for the production of butyl levulinate from fructose and butyl alcohol

Abstract

Today we get around 70,000 direct products from oil, which gives us an idea of the importance that it has in our economy. Approximately 90 % of the oil is used as raw material to produce energy and the rest for others chemical products. It is for this reason that the search for petroleum substitutes has been proposed for more than 100 years, with the use of biomass as a raw material being of major importance today, as biomass is the only source of carbon renewable from which it is possible to obtain biofuel and chemical products. Nowadays, studies are increasingly demanding towards the development of biofuels, focusing on the development of second- generation fuels. A good starting point is the lignocellulosic biomass, since it contains more than 50 % by weight of sugars, which can be transformed to very valuable platform molecules chemicals such as of levulinic acid. In this context, we propose to study the reaction between fructose and 1-butanol to produce butyl levulinate over thermostable ion exchange resins, a chemical candidate to be blended with diesel fuel. Besides mentioning that levulinate esters such as butyl levulinate are important chemical feedstocks having potential applications either in flavoring and fragrance industries or as already said in biodiesel as blending component. The aim of this work is to determine the catalytic behavior in terms of achieving total conversion of fructose, greater selectivity towards butyl levulinate and decrease the amounts in the generation of by-products (butyl formate, formic acid, etc.) by looking for the most suitable reaction conditions to be used in the industrial production of butyl levulinate. This research work evaluates the use of thermostable ion exchange resins which low and medium amounts of divinylbenzene in the production of butyl levulinate from fructose and butyl alcohol. The present work focuses on the synthesis of n-butyl levulinate using thermostable ion exchange resins AmberlysTM 45 and Purolite® CT-484, with maximum operating temperatures of 170 °C and 190 °C respectively, to catalyze the conversion of fructose to butyl levulinate in the butanol-water medium. With these resins, the temperature will be increased up to 170 °C. To check its effect on conversion of fructose and selectivity on products, especially to butyl levulinate. Further, a study for optimizing the reaction conditions such as fructose to 1-butanol molar ratio and catalyst concentration has been described.The effect of temperature was mainly checked in the range 120 -150 ºC at three fructose/1-butanol molar ratios (0.009, 0.013 and 0.0017) over three catalyst loading (1.7, 2.5 and 3.3%) with AmberlystTM 45 and Purolite® CT 482 as catalysts. At a constant RFruct/BuOH and Rcat(wt/wt) %, an increase of temperature led to an increase of both BL mole produced and BL yield, but also secondary reactions were promoted: DBE production increased dramatically (from 130 ºC), whereas BF and FA production increase was of the same level as BL. The same behavior was observed on changing the initial molar ratio. Consequently, the higher the temperatures, the lower fructose/ 1-Butanol molar ratios and the higher catalyst loading, the higher the fructose selectivity towards BL, but also for byproducts as BF, FA and DBE. In addition, in the opposite case for the 5-HMF and BMF, as the temperature increases the low selectivity for these by-products. The best conditions to obtain up to 55.6 % selectivity towards butyl levulinate and 99 % fructose conversion is working with Purolite® CT-482 resin, ratio of catalyst weight to initial load weight 3.3 %, molar ratio of fructose to 1-butanol 0.013, at a working temperature of 170 °C for eight hours of reaction.