Chemical and cellulose crystallite changes in Pinus radiata during torrefaction

The impact on the chemical composition and changes to the cellulose crystallites in Pinus radiata wood chips under light (ca. 230 °C), mild (ca. 260 °C), and severe (290+ °C) torrefaction temperatures at a range of times was examined by solid state 13C CP-MAS and Dipolar Dephased NMR spectroscopy, TGA, and synchrotron based X-ray diffraction. Results indicated the decomposition of hemicelluloses into furfurals at the lowest temperature with little modification to the lignin or cellulose. De-polymerisation of lignin and cellulose was observed as torrefaction severity increased. The increased hydrophobicity under light and mild torrefaction severity was attributed to a combination of thermo-chemical modifications to hemicelluloses and lignin, along with cellulose crystal lattice changes. The observed decrease in hydrophobicity under severe torrefaction conditions was attributed to the degradation of cellulose crystallites.