Chemical and thermal properties of precipitates made from hydrolysate of spruce wood chips

Autohydrolysis is a widely used technology for extracting hemicelluloses from wood chips. In addition to hemicelluloses, hydrolysates produced in this process contain lignin. Hemicelluloses and lignin could be isolated from hydrolysates and used for generating value-added products. In this study, hydrolysates were produced via autohydrolysis of spruce wood chips. Then, acidification and ethanol precipitation were employed to isolate lignocelluloses from hydrolysates. Generally, acidification and ethanol treatment led to the precipitation of lignin–carbohydrate complexes, but their removals depended on the hydrolysis conditions. The heat capacity ( C p ) of the dried hydrolysates was in the range of 0.41–0.45 J/g °C, while the precipitates of acidification and ethanol treatment had the C p of 1.18 J/g °C and 1.38 J/g °C, respectively. This increment could be related to their higher lignin content and thus their molecular mobility as these segments had a higher amount of methoxyl groups and more H α and H β inter-linkages. The results of this study suggested that the lignocellulosic materials obtained after acid or ethanol treatment of hydrolysates could be considered as additives for heat-resistant biopolymers or hemicellulose-based films, respectively.