Investigation of conditions for dilute acid pretreatment for improving xylose solubilization and glucose production by supercritical water hydrolysis from Quercus mongolica

The objective of this study was to prepare a feedstock, which xylose should be highly solubilized and most of the glucose remained in the solid fraction, for supercritical water hydrolysis (SCWH). Response surface methodology (RSM) with two independent variables (reaction time and sulfuric acid concentration) was adopted to find suitable conditions for pretreatment using a simple apparatus an autoclave for massive production. Based on the results of the RSM experiments, higher xylose contents were obtained in the liquid fraction after dilute acid pretreatment at 121 °C for 60 min with 6.82% H2SO4 (condition #8 (18.0%)) and at 121 °C for 102.3 min with 4% H2SO4 (condition #6 (16.0%)). To preventing corrosion of the apparatus, condition #6 was modified by prolonging the reaction time to 105 min, which led to a xylose content of 17.6% in the liquid fraction. Furthermore, structural degradation of the solid fraction was observed, indicating a positive effect for sugar production via SCWH.