Influence of Reaction Time, Temperature, and Heavy Metal Zinc on Characteristics of Cellulose- and Wood-Derived Hydrochars from Hydrothermal Carbonization

Hydrothermal carbonization (HTC) is a promising technique to convert biomass into valuable solid fuels. In this work, cellulose- and wood-derived hydrochars were synthesized under hydrothermal carbonization conditions with different temperatures (200-250 degrees C) and reaction times (6 h or 12 h). The content of fixed carbon in the cellulose-derived hydrochar is higher than that of the wood-derived hydrochar. Moreover, cellulose can be carbonized more easily during the HTC reaction than wood. O/C and H/C ratios of all hydrochars were similar to those of lignite and decreased with increasing reaction temperature. The composition of solids recovered after 12 h is similar at all temperatures, consisting primarily of sp(2) carbons (furanic and aromatic groups) and alkyl groups. When a large amount of metal is introduced, except for part of the zinc combined with the energetic group, the remaining part will condense on the surface of the sample as zinc ions.