Thermal analysis and pyrolysis – gas chromatography/mass spectrometry of fossil wood from the locality of Bükkábrány, Hungary

Abstract

Fossil wood that is ca 7 million years old from Bükkábrány (Hungary) was analyzed by thermogravimetry (TG), differential scanning calorimetry (DSC) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to evaluate alterations of its chemical composition. A wood sample of bald cypress (Taxodium distichum (L.) Rich.) from West Hungary was taken as a reference. The fossil wood was characterized by higher contents of total carbon (58.05 %) and total nitrogen (0.44 %) compared to recent wood. TG of fossil wood showed a high heterogeneity of wood substance, significant loss of polysaccharides and enrichment by lignin including more thermally stable components (> 500 °C). The enthalpy change (∆H) of combustion (thermo-oxidation) for fossil wood was significantly higher than for recent wood (–18.17 kJ/g vs. –11.41 kJ/g). Py-GC/MS analysis of fossil wood showed a significant depletion of polysaccharide pyrolysis products and an increase in lignin pyrolysis products compared to recent wood. The pyrolytic H/L ratio indicates a preferential loss of polysaccharides in fossil wood. Polysaccharide pyrolysis products were rare and represented mainly by levoglucosan. Lignin also underwent substantial changes. A dramatic decrease in monomers, an increase in short side chain compounds and the presence of demethylated/demethoxylated compounds in the composition of lignin pyrolysis products are indicative of lignin alteration (degradation). Moreover, a high abundance of styrene, cresols, phenol and phenolic compounds was observed.

Keywords

• hermogravimetry
• differential scanning calorimetry
• analytical pyrolysis
• evaluation of chemical composition alterations of fossil wood
• bald cypress (taxodium distichum (l.) rich.)
• western hungary