Pyrolysis of furfural residue pellets: Physicochemical characteristics of pyrolytic pellets and pyrolysis kinetics

Biomass pelletization technology has recently gained significant interest, where pyrolyzed pellets have a very wide range of applications (e.g., as pellet fuels and adsorbents). In this study, furfural residue pellets (FRPs) were pyrolyzed at temperatures of 200–850 °C in a tube furnace. The physical and chemical properties of the pyrolyzed FRPs (PFRPs) obtained at various temperatures were compared, and the kinetic parameters of the pyrolysis process were calculated using the distributed activation energy model (DAEM). The PFRPs prepared at 450, 650, and 850 °C had higher volumetric energy densities than coal, whereas other properties (e.g., H/C and O/C ratios) were found to be similar to those of coal. The maximum iodine adsorption value (i.e. 317.8 mg/g) and methylene blue adsorption value (i.e. 96.4 mg/g) were achieved by pyrolysis at 650 °C and 450 °C, respectively, indicating that pyrolysis promoted the formation of micropore structures at 650 °C. Two-dimensional correlation spectroscopy (2D-COS) was employed to explore the temperature-sensitivity of the surface functional groups of the PFRPs. Based on comparison of the volumetric energy density, hydrophobicity, particle density, and strength, the PFRPs prepared at 250–300 °C afforded the best overall performance, where the sample prepared at 300 °C exhibited the maximum hydrophobicity.