Reaction Kinetics of Levulinic Acid Synthesis from Glucose Using Bronsted Acid Catalyst

Abstract

Glucose is one of the primary derivative products from lignocellulosic biomass, which is abundantly available. Glucose has excellent potential to be converted into valuable compounds such as ethanol, sorbitol, gluconic acid, and levulinic acid (LA). Levulinic acid is an exceptionally promising green platform chemical. It comprises two functional groups, ketone and carboxylate, acting as highly reactive electrophiles for a nucleophilic attack. Therefore, it has extensive applications, including fuel additives, raw materials for the pharmaceutical industry, and cosmetics. This study reports the reaction kinetics of LA synthesis from glucose catalyzed by hydrochloric acid (HCl), a Bronsted acid, that was carried out under a wide range of operating conditions; i.e. the temperature of 140–180 °C, catalyst concentration of 0.5–1.5 M, and initial glucose concentration of 0.1–0.5 M. The highest LA yield of 48.34 % was able to be obtained from an initial glucose concentration of 0.1 M and by using 1 M HCl at 180 °C. The experimental results show that the Bronsted acid-catalyzed reaction pathway consists of glucose decomposition to levoglucosan (LG), conversion of LG to 5-hydroxymethylfurfural (HMF), and rehydration of HMF to LA. The experimental data yields a good fitting by assuming a first-order reaction model. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Experimental and Kinetic Modeling of Galactose Valorization to Levulinic Acid

“…They found that galactose was converted almost completely in the first 5 min at a temperature of 188 °C, while the optimum yield of 40.7 mol% was achieved at 20 min. The same effect was found by Toif [30] who studied the synthesis of LA from glucose with HCl as the catalyst and by Fachri [29] who studied the synthesis of LA from fructose with H2SO4 as the catalyst. shows that at the same reaction time, the higher the acid concentration level, the higher and faster the galactose conversion.…”

“…This data also implies that adding an acid catalyst to the decomposition of galactose does not lead to the desired reaction by producing more yield but to an undesired reaction for the formation of by-products. Such effect of the acid catalyst also occurred in the decomposition of fructose and glucose [16,[28][29][30], where galactose produced insoluble byproducts more than fructose and glucose did [21].…”

“…LA synthesis has been widely studied using hexose as a raw material with homogeneous acid catalysts, both mineral and organic acids [16,[27][28][29][30] and heterogeneous acid catalysts [20,[31][32][33][34]. Fructose and glucose, compared to galactose, are commonly studied because of the molecular structure of fructose and the location of the carbonyl group that make the conversion to 5-HMF more favorable.…”

“…As a result, it makes glucose to be more attractive. Glucose is the second most studied C6-sugar in LA production because it is a constituent of almost all biomass generations [16,20,27,30]. Table 1 shows an overview of LA production from C6-sugar under various operating conditions.…”

“…Previous studies that addressed the decomposition of C6-sugar, indeed, reported the effects of temperature, acid concentration, and substrate loading on LA production [16,[27][28][29][30][31][32][33][34]. However, only a few of them reported C6-sugar derived from galactose.…”