When anthracene oil (AO, 280°C+) was carbonized at atmospheric pressure, it produced a coke of flow texture at coke yield of only 3 wt%. Although the modification of AO by catalytic hydrogenation (HAO-I and -II) increased its hydrogen content, the resultant oil failed to carbonize. On the other hand, hydrogenated AO using Li and ethylenediamine (HAO-III) formed a coke of excellent flow texture at 9 wt% yield (Fig. 1 and Table 1) although its H/G atomic ratio was highest for the hydrogenated oils. The content of beta hydrogen in the 1H-NMR spectra of HAO-III was much higher than that of HAO-I and of HAO-II, indicating different naphthenic partial structures. Oxidation of AO by air blowing increased the coke yield up to 34 wt% (AOox-3) as shown in Table 2, but size of the optical texture decreased with increasing of coke yield. HAO-Iox-2 and HAO-IIox-2 gave cokes of flow texture at yields of 9 and 5 wt%, respectively. The air blown HAO-III (HAO-IIIox-2) markedly increased its coke yield up to 22 wt%. It is of interest to note that the coke resulted from HAO-IIIox-2 maintained an excellent flow texture which is the same as that before air blowing. The profile of 1H-NMR spectrum of HAO-III in the aliphatic region was different from that of HAO-II (Fig. 2), indicating different naphthenic structures. Although almost a half of the beta hydrogen in both HAO-II and -III remained even after air blowing (Fig. 3), the gel permeation chromatograms in Fig. 5 showed that the pitch from HAO-IIIox-2 contained a larger amount of heavier fractions than the other oxidized pitches. These facts suggest two types of naphthenic hydrogen exhibiting different reactivities. Both types of hydrogen are introduced by chemical hydrogenation, whereas hydrogens of greater stability is introduced only by catalytic hydrogenation. The behavior of these types of hydrogen in air-blowing and the carbonization stages are illustrated schematically in Fig. 6.
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