Charcoals were produced from spruce and beech wood under laboratory conditions at different pyrolysis temperatures (300–1300 °C). Characterization of these charcoals was conducted using eight analytical methods. Each method describes specific changes in the temperature range until 1300 °C. Therefore, the combination of these methods provides comprehensive information on different pyrolysis stages. Fourier transform infrared (FTIR) spectroscopy, NMR spectroscopy, and thermogravimetry display changes until 700 °C. A prediction model for pyrolysis temperature until 800 °C is presented based on FTIR spectra with an R 2 of 0.98. He-pycnometry resolves the temperature range between 500 and 890 °C. Small angle X-ray scattering (SAXS) describes precisely the evolution of the porous structure and completes the set of techniques by a description of the physical properties of the charcoal. X-ray diffraction (XRD) reveals the crystallographic change of the lignocellulosic structure toward precursors of graphite. The formation of calcite out of CaO and CO2 becomes evident.

No abstract

No abstract

Oak heartwood usually darkens during and after drying. This darkening can be heterogeneous, leaving non-colored areas in the wood board. These light discolorations have been linked to heterogeneous distribution of tannins, but compelling evidence on the microscale is lacking. In this study Raman and fluorescence microscopy revealed precipitations of crystalline ellagic acid, especially in the ray cells but also in lumina, cell corners and cell walls in the non-colored areas (NCA), which also had higher density. In these denser areas free water is longer present during drying and leads to accumulation of hydrolyzed tannins. When eventually falling dry, these tannins precipitate irreversible as non-colored ellagic acid and are not available for chemical reactions leading to darkening of the wood. Therefore, pronounced density fluctuations in wood boards require adjusting the drying and processing parameters so that water domains and ellagic acid precipitations are avoided during drying.