Changes in the content and composition of the extractives in thermally modified tropical hardwoods

Abstract

Chemical composition of wood is known to change during thermal treatments. Two species grown in Turkey, afrormosia (Pericopsis elata) and duka (Tapirira guianensis) were heat treated according to Ther-mowood® method. Lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol and water were determined. Wood extracts were analysed by gas chromatography with mass detection and existing compounds were identified by NIST17 database. Results show that hemicelluloses and cellulose content decreased for both heat-treated woods along the treatment while lignin percentage increased. The analysis of extractives has shown several compounds normally associated to lignin thermal degradation that increased along the treatment. At the same time several compounds associated to carbohydrate thermal degradation were found in all the extracts for both heat-treated woods. These founding have allowed the understanding of the degradation pattern of wood during thermal modification. There was not much difference between afrormosia and duka woods structural compounds behaviour along thermal modification. However, the variation of the amount of extractives along the treatment depended on the species.

Characterization of Acrocarpus fraxinifolius wood submitted to heat treatment

“…The extractives content gradually increased with the increase in the treatment temperature, from 2,1 %, of untreated wood, to up to 30,9 %. Increased content of heat-treated wood extractives has been reported in the literature by Esteves et al (2011, Esteves et al (2022), Lengowski et al (2021) and Lopes et al (2022). It was also observed in the heat treatment of wood particles (Crespo et al 2014), as well as in heat treated wood by different methods, as in the heat treatment with silicone oil studied by Okon and Udoakpan (2019).…”

“…According to Esteves et al (2008) and Esteves et al (2022), the original extracts of the wood are almost or totally degraded during the heat treatment, with the increase in the content of extracts observed related to the changes caused in the lignin content and mainly in the degradation of hemicellulose, which results in the formation of new chemical compounds, which are extracted during extractives analysis.…”

Chemical Composition and Optimization of Liquefaction Parameters of Cytisus scoparius (Broom)

“…These extractives are important since they proved to be good for the preparation of formulations for topical application to protect skin against oxidative damage [6,35]. Dichloromethane removes mostly non-polar extractives such as fatty acids, alkanes, waxes, terpenes and terpenoids, as stated before [36]. On the other hand, ethanol extractives are generally composed of lignans, flavonoid, stilbenes and mostly tannins (hydrolyzable and condensed).…”

FTIR spectroscopy and technological characterization of heat treated Fraxinus excelsior wood

“…Heat treatment volatilizes some classes of compounds, mainly phenolics, but the depolymerization of hemicelluloses generates compounds that remain connected to the fibers through weak bonds. These compounds can be removed with solvents used to quantify extractives (Zanuncio et al, 2015;Mecca et al, 2019;Esteves et al, 2022), resulting in an increase in extractives content from 6.59% to 8.25%. Finally, lignins have a high carbon content and strong bonds between their monomers, which makes them highly resistant to thermal degradation (Zanuncio et al, 2018;Börcsök;Pásztory, 2021).…”