Varied impacts of volatiles from pyrolysis of poplar wood, bark and leaves on property of coal char

Co-pyrolysis of coal and biomass could tackle undesirable properties associated with coal-tar or bio-oil, while cross-interactions between volatiles and chars of varied origin are very complex but important in shaping property of pyrolytic product. Herein, the volatiles from pyrolysis of poplar wood, bark or leaves were forced to pass through coal-char in lower bed at 600 ºC, aiming to investigate specific interactions of the volatiles with the coal-char. The results indicated that the biomass-derived volatiles did interact with the coal-char and formed additional carbonaceous deposit via mainly cracking reactions, increasing yield of coal-char (i.e. 7.1 % increase with wood-derived volatiles while 19.6 % increase with leaves-derived volatiles). Cracking of volatiles from poplar wood or bark on coal-char formed very aromatic carbonaceous deposit, enhancing overall carbon content while causing coarse surface of the coal-char. The leaves-derived deposit was more oxygen-rich, which, however, still enhanced thermal stability and crystallinity of graphitic carbon crystals in the modified coal-char. Additionally, the coal-char modified with the biomass-volatiles became more hydrophobic, despite the increased abundance of the oxygen-containing species like CO and C–O–C. The modification of elemental composition and aromaticity of coal-char through interaction with the biomass-derived volatiles resulted in higher capability for adsorption of phenol. [Display omitted] •Cracking of poplar-derived volatiles on coal-char forms additional deposit.•Deposit from volatiles of wood/bark is C-rich, while that from leaves is O-rich.•Interaction between volatiles and coal-char forms O-containing species like CO and C–O–C.•Coal-char modified by volatiles shows superior capability for adsorption of phenol.•Modified coal-char has higher aromatization degree, thermal stability and hydrophobicity.