Effects of extractives on degradation characteristics and VOCs released during wood heat treatment

Eucalyptus was applied to investigate the influence of extractives on thermo-degradation of wood during heat treatment. Degradation characteristics, specifically the thermal degradation kinetics and volatile products during the heat treatment, were studied. A kinetic analysis was performed based on the Arrhenius equation and the time-temperature superposition principle. A devolatilization analysis was then conducted according to the chromatography identification. The results showed that the extractives facilitated the thermo-degradation and initiated the degradation at a lower temperature. An earlier degradation starting point was detected, and a lower activation energy of 65.7 kJ/mol was calculated for the non-extracted Eucalyptus. The VOCs collected in this research were primarily acetates, furans, terpenes, and other compounds. The non-extracted specimen released more VOCs than the extracted specimen. Compared with extracted samples, further hemicellulose degradation was identified for the non-extracted samples at the whole stage of 180 °C and a temperature-elevating period of 200 °C, as well as lignin decomposition at the temperature-holding section of 220 °C. However, only hemicellulose degradation was observed in extracted samples. This research could be helpful for the mechanism explanation of wood heat treatments and to promote the process to be more efficient and environmentally friendly.