Study on the degradation of xylose residue in hydrothermal treatment process

Abstract Degradation of xylose residue (XR) was carried out in hydrothermal treatment process (HTP) at various temperatures, residence times, solid–liquid ratios, and particle sizes. The properties of liquid, gas, and solid (hydrochar) products were investigated in anticipation of obtaining the process conditions for the preparation of optimum‐performance hydrochar. It was found that temperature was the most important factor affecting hydrothermal treatment process. For hydrochar, as the temperature rose from 200 to 320°C, the mass yield (MY), volatile matter (VM), and blackness value decreased, but the fixed carbon (FC) content and high heating value (HHV) increased. Compared with XR, the VM of hydrochar decreased from 87.97% to 30.3%, FC content increased from 8.23% to 68.91%, and HHV increased from 17.88 MJ/kg to 28.62 MJ/kg. The best data obtained from hydrochars were the iodine value, 89.03 g/kg, and DBP value, 190 cm 3 /g, which were quite close to that of the commercial carbon black. The gas chromatography coupled to a mass spectrometry (GC–MS) characterization indicated that ketones, phenols, organic acids, and furans were the main components in bio‐oil (the maximum yield of 19.22%). The contents of ketones and phenols increased with the temperature, and the highest relative contents were up to 29.54% and 32.84%, respectively. The gas and loss product yield reached its highest, 61.31%, at 320°C. CO 2 dominated in gas‐phase fractions, accounting for about 90%. H 2 , CO, and CH 4 were clean and efficient energy sources, but were too few. This study was expected to transform XR into high value‐added products and provided new ideas for the resource utilization of waste.