Levulinic acid production by solid-catalyzed treatment of liquid hydrolyzate obtained from pretreatment of lignocellulosic biomass

Hemicellulosic sugars released into liquid fraction during lignocellulosic biomass pretreatment have been frequently targeted in a field of bioenergy research due to its simple separation process, abundant amount among carbohydrates, and numerous application methods. For instance, xylose produced from bio-refinery process could be traditionally used as a source of furfural, xylitol, bioethanol, and other value-added derivatives. In recent years, as more insightful procedures for a catalytic conversion of lignocellulosic biomass have been introduced, the possibility to produce levulinic acid from xylose or furfural has been proposed by several previous studies. C5 sugars could undergo dehydration to become furfural, and then furfural could be converted into furfuryl alcohol, and subsequently, into levulinic acid through a transfer-hydrogenation reaction which offers an attractive alternative to molecular H₂ for the reduction of targeted functional groups.
Therefore, the aim of this study was to produce levulinic acid by solid-catalyzed treatment of the liquid hydrolyzate obtained by the pretreatment of lignocellulosic biomass (reaction temperature: 150°C, reaction time: 10 min, catalyst: 1% (w/w) H₂SO₄). Zeolite was used as a solid catalyst though alkaline treatment depending on alkali concentration. Considering the effects of other treatment factors (reaction temperature (150-210°C) and time (30-300 min)), approximately 25% of reducing sugar in the liquid hydrolyzate was converted into levulinic acid at reaction temperature of 190°C and reaction time of 180 min when using zeolite treated by 0.25 M NaOH.