Hydrothermolysis of pine wood

The objective of this research was to obtain a better fundamental understanding of the extraction of lignin and carbohydrates from pine wood during hydrothermolysis at elevated temperatures. The treatment was performed in a batch reactor at three different temperatures (200, 220 and 240 °C) and a liquid-to-wood ratio of 40:1. It was found that up to 35% of native pine lignin solubilized at 240 °C within a few minutes of reaction time. Delignification kinetics of wood during hydrothermolysis was successfully modeled by the assumption of simultaneous dissolution (depolymerization) and condensations reactions of lignin. Two distinct lignin fractions, so-called soluble and insoluble lignin were found in the hydrolysates and can be considered as potential material for the production of high-value products. Complete removal of pine wood hemicellulose was achieved at a concomitant cellulose yield loss of about 12.5%. Up to 85% of pine wood mannan could be recovered from the hydrolysate as manno-oligosaccharides, in contrast to only 46% of xylo-oligosaccharides. Kinetic models fitting experimental data are proposed to explain degradation and conversion reactions of two main hemicellulosic components of pine wood, xylan and mannan. Overall, this study provides initial fundamental knowledge required for potentially efficient utilization of softwoods using wood biorefinery concept.