thermogravimetry-infrared spectroscopy analysis of the pyrolysis of willow leaves, stems, and branches

The pyrolysis of willow samples from various plant positions was analysed using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). The results indicate that pyrolysis can be divided into four stages. The first stage from 30 to 120°C involves free evaporation of moisture, with a mass loss of 5%. The second stage from 120 to 200°C involves the pyrolysis of hemicellulose and unstable cellulose, with a mass loss of 4%. The third stage is from 200 to 400°C, with a weight loss of 60%, in which the chemical components of wood thermally decompose and emit heat, carbon dioxide, and so on. In the final stage, which occurs above 400°C, the pyrolysis of lignin and charring of cellulose occur, with a mass loss of 10%. Moreover, in FTIR, the samples exhibit the highest absorbance during the main pyrolysis phase, from which wood vinegar ingredients mainly arise, including CO2, H2O, CO, and small amounts of hydrocarbons, alcohols, phenols, acids, esters, and aromatic compounds. Additionally, leaves are decomposed more thoroughly before the main pyrolysis phase, whereas decomposition of branches occurs fullest during this phase. Finally, we put forward some suggestions to support further research on conversion of willow into wood vinegar products.