Hydrothermal degradation of hemicelluloses from triploid poplar in hot compressed water at 180-340 ℃

摘要

Hemicelluloses isolated from triploid poplar were subjected to hydrothermal degradation at 180-340 ℃ The detailed physicochemical characteristics of hydrothermal degradation products including mono-saccharide and XOS, molecular weight, inhibitory and organic compounds were detected by HPAEC, GPC, HPLC, and GC-MS, respectively. An increase in temperature led to a significant decrease in molecular weight and an increase in C_2-C_5 organic alcohols and acids. More importantly, besides two well-known routes that hemicelluloses are hydrolyzed to monosaccharide, followed by further degraded to furfural, a series of reaction routes was proposed to clarify and explain the mechanisms of the hydrothermal degradation of hemicelluloses from triploid poplar, which involved: (ⅰ) a predominant route of fragmentation; (ⅱ) side reactions such as oxidation, dehydration, isomerization/rearrangement, and self-lactonization; (ⅲ) larger molecular fragments from sugars by deoxydation or/and oxidation, followed by self-lactonization; and (ⅳ) very few extensive re-polymerization including esterification and condensation among hemicelluloses and lignin fragments.