Emissions from thermally modified beech wood, their reduction by solvent extraction and fungicidal effect of the organic solvent extracts

摘要

The characterization and removal of odorous substances caused by thermal treatment of wood were investigated using chromatographic and spectroscopic methods. Emissions of pentanal and hexanal, probably formed by oxidation of unsaturated fatty acids, were the prevailing aldehydes in untreated wood samples. Their amount decreased during thermal treatment, while furfural and 5-methylfurfural (degradation products of hemicelluloses) accounted for almost 100% of the aldehyde fraction. Furthermore, it can be assumed that odorous emissions of thermally modified wood can be strongly reduced by solvent extraction. An ethanol-cyclohexane mixture that produces wood samples without significant odour emissions obtained good results. Certain organic solvent extractives from thermally modified beech have fungicidal properties. Methanol extracts, resolubilized in propanone, caused a retardation of fungal growth on native beech specimens. Beech specimens impregnated with these extractives could be assigned to durability class 4 (not permanent). The analysis of methanol extracts using gas chromatography coupled with mass spectrometry showed an increased share of phenolic compounds known to cause resistance effects. Their presence in organic extracts of thermally modified wood may explain the improved resistance of the impregnated specimen.