Hydrolysis of eucalyptus wood chips under hot compressed water in the presence of sulfonated carbon-based catalysts

Hydrolysis of lignocellulosic biomass to sugars and derivatives is a key step in production of biofuels and commodity chemicals in a biorefinery. In this study, catalytic hydrolysis of eucalyptus chips with solid sulfonated carbon-based catalysts prepared from three different carbon precursors (sucrose, glucose, and xylose) was studied under hot-compressed water at 150-250 °C with reaction time of 1-10 min. Increasing temperature up to 200 °C led to higher sugar yields from cellulose and hemicellulose while further increase in temperature caused higher formation of sugar degradation by-products. Sulfonated-sucrose (SO3H-Suc) showed the greatest performance on sugar production compared to other catalysts with less formation of furans and anhydroglucose; its high catalytic activity was related to its high acid site density as proven by NH3-TPD measurement. Size reduction and chemical pretreatment of the biomass were found to enhance the hydrolysis yield and reaction selectivity. The highest sugar yield of 40.7% comprising glucose, fructose, and xylose was achieved using 5% (w/w) SO3H-Suc at 200 °C for 5 min with milled biomass (60-100 μm) pretreated by alkaline oxidation. The work provides an alternative catalytic process for hydrolysis of lignocellulose in biomass industry.