Study on the catalytic pyrolysis of coal volatiles over hematite for the production of light tar

•A hematite catalyst was used for pyrolysis tar upgrading.•Hematite A and B decreased the pitch content by 7.59 and 8.88 % respectively.•Catalytic pyrolysis of coal enhanced the content of Fe2+ in hematite.•Fe and lattice oxygen were the decisive factors in the bond cleavage of heavy tar.