Effect of hot-water extraction of sugar maple on organosolv delignification and lignin recovery

This paper reported a gradual disassembly of the chemical components of hardwood, starting with hot-water extraction (HWE) for the removal of hemicelluloses, followed by organosolv delignification to remove the lignin. Under mild acid conditions, in addition to hemicelluloses, lower molecular weight lignin fractions were removed (~15% of the total lignin) in the HWE pre-treatment; also, the cleavage of the acid-labile lignin-carbohydrate bond took place to some extent. As a result, the HWE pretreatment promoted the subsequent delignification process and facilitated the lignin recovery from the spent liquor, in terms of higher delignification efficiency and higher purity of the lignin recovered from the spent liquor. The effects of the HWE pre-treatment prior to the delignification process were investigated in this study for both the oxygen-pressurized acetone-water (AWO) and the ALCELL processes, with focuses on the delignification efficiency and the properties of the lignin recovered from the process spent liquor.