Enhanced production of xylose from corncob hydrolysis with oxalic acid as catalyst

The acid-catalyzed treatment was a conventional process for xylose production from corncob. To increase the release of xylose and to reduce the by-products formation and water usage, the oxalic acid was used as catalyst to hydrolyze the corncob and the hydrolytic conditions were investigated. The highest xylose yield of 32.7 g L^-1, representing 96.1% of total theoretical xylose yield, was obtained using 1.2% oxalic acid after hydrolysis for 120 min at 130 °C, which was more than 10% higher than that of sulfuric acid-catalyzed hydrolysis. Mixed acids-catalyzed hydrolysis performed a synergistic effect for xylose production and 31.7 g L^-1 of xylose was reached after reacting for 90 min with oxalic acid and sulfuric acid at a ratio of 1:4 (w/w). A kinetic model was developed to elucidate the competitive reaction between xylose formation and its degradation in the hydrolysis process, and the experimental data obtained in this study were perfectly in agreement with that of predicted from the model. Furthermore, the final xylose yield of 85% was achieved after purification and crystallization. It was demonstrated that xylose production from the corncob hydrolysis with oxalic acid as the catalyst was an effective alternative to the traditional sulfuric acid-based hydrolysis.