WOOD SCIENCE AND TECHNOLOGY, vol.57, no.4, pp.945-964, 2023 (SCI-Expanded)
The hydrothermal carbonization of walnut wood chips was conducted at 200-250 & DEG;C for 1-8 h. Increasing the hydrothermal carbonization temperature or the residence time decreased the volatile products and increased the fixed carbon content of the hydrochars. The hydrochars produced from the non-catalytic experiments at 250 & DEG;C for 6 and 8 h were in the lignite class. The lowest O/C and H/C atomic ratios were obtained after carbonization at 250 & DEG;C for 8 h. The catalytic hydrothermal carbonization experiments were carried out in the absence and presence of InCl3 using 1, 2, and 4 mmol of InCl3 at 200, 225, and 250 & DEG;C for 4 h. The highest heating value of hydrochar from the catalytic experiment was 24.73 MJ/kg and was obtained at 250 & DEG;C for 4 h using 1 mmol InCl3. Process water reuse resulted in increased heating values of the hydrochars in both the non-catalytic and catalytic experiments. The use of InCl3 promoted the coalification degree of the hydrochars. These results demonstrate that InCl3 is a suitable catalyst for producing hydrochars via the hydrothermal carbonization of walnut wood chips, which can be used as a solid biofuel.