Autocatalytic modification of coal tar pitch using benzoyl chloride and its effect on the structure of char

•Coal tar pitch (CTP) was successfully modified by benzoyl chloride (BC).•BC was used as both a modifying agent and a catalyst.•No new impurities are introduced with BC in the modified process of CTP.•Toluene insoluble of modified CTP increased by 114 % compared with that of CTP.•Modified CTP produced a char with a desirable fibrous structure.

Benzoyl chloride (BC) is used as both a modifier and a catalyst to successfully modify coal tar pitch (CTP). The char structure formed by the modified coal tar pitch (MCTP) was investigated in this study, and the results showed that the softening point, coking value, and β-resin content of MCTP increased in comparison with those of CTP. Effects of modification conditions, such as temperature, ratio of BC to CTP, and time on the char structure, were studied by polarized light microscopy, XRD, FT-IR, and 1H NMR. Ordered, fibrous structures were produced at optimal conditions in char as a result of the carbonization of MCTP. The optimal conditions were as follows: modification reaction time of 15 h, reaction temperature of 150 °C, and BC to CTP ratio of 5 wt.%. Data from the XRD spectra indicated that the interplanar crystal spacing of the char, which was obtained after MCTP carbonization, was 0.339 nm, which is close to the crystal structure of graphite. The crystallite height of the MCTP char was higher than that of the CTP char. A possible reaction mechanism is therefore proposed in this paper.