The role of hydrogen bonding and melting behaviors on H2 production during alkaline thermal treatment of lignocellulose

The interactions between the three major components of lignocellulose significantly affect the thermochemical conversion process and product distribution. Herein, the role of hydrogen bonding and the melting behaviors among the three major components on different H 2 production stages during alkaline thermal treatment (ATT) of lignocellulose are revealed for the first time. The melting behavior of xylan (120 ∼ 210 °C) and the unique hydrogen bonding between cellulose and xylan reinforced by molten xylan (120 ∼ 160 °C) are essentially responsible for the hysteresis of dehydrogenation and formation of active char (160 ∼ 235 °C). Hydrogen bonding gradually disappears during the formation and further reaction of active char. The melting behavior of xylan also hinders the mass transfer of gaseous products at 235 ∼ 350 °C and promotes the methanation reaction of active char. The slight melting behavior of lignin (200 ∼ 250 °C) has minimal effect on the dehydrogenation process, but exacerbates the carbonization reaction of the ATT process, leading to a decrease in H 2 production. Subsequently, the conversion of char is the main reaction above 350 °C and increasing the alkali addition facilitates the efficient conversion of char. Especially, the small discrepancy between the fitted and experimental values of H 2 production from ATT of real lignocellulose provides new insights into establishing a predictive model for H 2 production based on the three major components.