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

Abstract

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 15h, reaction temperature of 150°C, and BC to CTP ratio of 5wt.%. Data from the XRD spectra indicated that the interplanar crystal spacing of the char, which was obtained after MCTP carbonization, was 0.339nm, 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.