Pressure-assisted hydrothermal pretreatment for biorefinery to enhance pulp production

Abstract

The efficient removal of hemicelluloses while preventing cellulose hydrolysis is crucial in Kraft pulping yet remains challenging. Herein, a mild pressure-assisted hydrothermal pretreatment strategy was developed in this study prior to Kraft pulping. Research indicated that pretreatment at 155 °C under 3 MPa pressure significantly enhances hemicelluloses removal (to 70.63 %), surpassing even that at 165 °C under ambient pressure. Moreover, during pre-hydrolysis Kraft pulping, pressure-assisted hydrothermal pretreatment could reduce the concentration of active alkali used in the subsequent pulping process. The cellulose properties (viscosity = 491 ml/g) and purity (R10 = 94.60 %) of bleached pulp obtained from pressure-assisted hydrothermal pretreatment outperform those obtained from conventional hydrolysis. Furthermore, the removed hemicelluloses were converted into monosaccharides and polysaccharides to produce high-value chemicals in downstream processes. Therefore, pressure-assisted hydrothermal pretreatment not only enhanced hemicelluloses removal and pulp properties but also reduced alkali concentration in the subsequent pulping process, promoting sustainable development in pulp production.