Impact of Pyrolysis Temperature on Charcoal Characteristics

Charcoals were produced from spruce and beech wood under laboratory conditions at different pyrolysis temperatures (300-1300 degrees C). Characterization of these charcoals was conducted using eight analytical methods. Each method describes specific changes in the temperature range until 1300 degrees 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 degrees C. A prediction model for pyrolysis temperature until 800 degrees C is presented based on FTIR spectra with an R-2 of 0.98. He-pycnometry resolves the temperature range between 500 and 890 degrees 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.