Two-step acid-catalyzed conversion of Quercus mongolica into levulinic acid

In recent years, as concept of biorefinery has been introduced, multi-step treatment process of lignocellulosic biomass has been developed for overcoming its recalcitrance and economic enhancement of biomass utilization (fuels, chemicals, and power). Among the producible chemicals from biorefinery process, levulinic acid has a high potential of economic value as renewable platform chemical and offers a large family of derivatives. Therefore, this study aims to investigate a two-step acid-catalyzed conversion of Quercus mongolica into levulinic acid.

In this study, small diameter log of Quercus mongolica (glucan: 39.1%, xylan: 15.5%, arabinan: 1.4%, galactan: 1.4%, mannan: 1.1%) was used, including bark. The 1^st step treatment was conducted using dilute sulfuric acid (solid/liquid ratio=1/6 (w/v)). After 1^st step treatment, solid hydrolyzate was recovered and reacted in 2^nd step treatment using sulfuric acid and/or inorganic catalyst, while liquid hydrolyzate was kept for utilization of C5 sugars. After treatment, levulinic acid and sugars in the liquid fraction were analyzed by high performance liquid chromatography (column type: Aminex HPX-87H and CarboPac PA1). As a result, 1^st step treatment conditions were optimized to maximize the C5 sugar extraction (reducing xylose: 14.8%) and minimize the glucose loss from Quercus mongolica (temperature: 140 °C, acid concentration: 2% (w/w), time: 10 min). Solid hydrolyzate (glucan: 49.0%) was used in 2^nd step treatment and the highest yield of levulinic acid (12.9%) was shown in the condition, which was consisted of a temperature of 200 °C, a 2 % sulfuric acid concentration, and at 10 min.