Hydrolysis of biomass by using transition metal oxide catalyst

Abstract

Agarose and microalgae have sugars that can make valuable products. Developing hydrolysis process to get fermentable sugar is main issue. Generally, hydrolysis of biomass uses acid catalyst, such as sulfuric acid, nitric acid, or hydrochloric acid. However, neutralization and desalting processes needed for production of sugar that is suitable for use as fermentation. In this work, layered transition metal oxide, $HNbMoO_6$, used as solid acid catalyst that shows great performance in hydrolyzing sugars such as sucrose, starch and even cellulose. 43.2%, 44.2% of galactose yield obtained in the condition that was 10g/L of agarose using 26.6g/L of $HNbMoO_6$ and 0.05N sulfuric acid at 120 oC. Layered $HNbMoO_6$ can be recycled at least two times with slight loss in catalytic performance. Although there was big loss after three times, regeneration process solved the loss problem. $HNbMoO_6$ was recycled 8 times with two times of regeneration process and obtained 95% maximum sugar yield compared to the first hydrolysis reaction. In microalgae cases, Chlorella and Nannochloropsis species used for hydrolyzing. 81.3% and 80.2% maximum sugar yield obtained using 20g/L of Chlorella ABC001 and HS1 in the condition that 53g/L $HNbMoO_6$ at 150 oC. However, in Nannochloropsis cases that have thick cell walls, sugar yield shows big difference between using solid and acid catalyst. Chlorella ABC001 also shows great performance in high concentration which obtained 74.8% of sugar yield. Because of microalgae is not soluble in water, solid-solid is difficult to separate. To overcome this problem, calcination method used for separation. Hydrolysate was calcination at 580 oC in order to get rid of microalgae. In addition, through optimizing the condition of calcination and mixing process, 50g/L of Chlorella ABC001 shows 3 times of recycle to obtain valuable sugar products.