Characteristics of the mesophase and needle coke derived from the blended coal tar and biomass tar pitch

Abstract In this work, coal tar pitch was co-carbonized with biomass tar pitch to manufacture hybrid mesophase pitch as precursor for the preparation of needle coke. The properties of mesophase pitches were characterized using a polarized light optical microscope, apparent viscometer, FT-IR, and 1H NMR. After adding biomass tar pitch into coal tar pitch, the mesophase pitches had more flow domain-like texture due to its lower viscosity and softening points. Besides, the addition of biomass tar pitch altered the chemical structure and functional groups of the resulting mesophase pitch, accompanied by the growth of alkyl and naphthenic compounds. Accordingly, the needle coke prepared from the hybrid mesophase pitches showed more flow domain textures and were better aligned uniaxially than the counterpart derived from pure coal tar pitch. The coefficient of thermal expansion of needle coke was reduced from 0.93 × 10-6  °C-1 to 0.42 × 10-6  °C-1. The low viscosity of the mesophase pitches caused by the addition of biomass tar pitch favored the development of mesophase and highly uniaxial arrangement. The increase in the alkyl and naphthenic group compounds greatly improved the performance of the needle coke.