Hydrothermal carbonization of forestry residues: influence of reaction temperature on holocellulose-derived hydrochar properties

The main objective of the present study was to investigate the influence of reaction temperature for hydrothermal carbonization (HTC) of holocellulose which came from the forestry residues, miscellaneous wood fibers. The temperatures of HTC ranged from 200 to 240 °C and the reaction time was controlled at 8 h. The structural, chemical, and thermal properties of holocellulose-derived hydrochar were characterized using scanning electron microscopy, X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy, elemental analysis, and TGA. According to the results, reaction temperature has a significant influence on the properties of the holocellulose-derived hydrochars. With increasing the HTC temperature, the wood-cellulated holocellulose converts into micro/nano carbon spheres gradually along with the disappearing of cellulosic crystalline region. The chemical composition of the hydrochars tends to be stable with elevating the temperature. The resultant hydrochar products with high degree of aromatization possess a large amount of oxygen-containing functional groups. Moreover, the energy content and thermostability of the hydrochars are considerably improved with increasing the HTC temperature. The attained results enable properties prediction of holocellulose-derived hydrochar from these forestry residues and contribute to understand the influence of process conditions on HTC of crude biomass.