Investigation of the Dependence of the Softening Temperature on the Content of Mesophase in Petroleum Pitches Obtained from Heavy Pyrolysis Resin and Decant Oil

Samples of petroleum pitches were obtained from heavy pyrolysis resin and decant oil (heavy gas oil of catalytic cracking) by thermal polycondensation at atmospheric pressure, at temperatures of 380-400 and 410-440 degrees C (for the resin and decant oil respectively), and with isothermal holding times of 30-480 min. Analysis of the dependence of the softening point on the mesophase content for the obtained samples showed that at the same mesophase content the pitches from decant oil exhibit a lower softening point compared with the pyrolysis resin pitches, for which the softening point approaches 300 degrees C even with 30 % of mesophase. This suggests that it is impossible to obtain pitches from pyrolysis resin with a high mesophase content without preliminary preparation. On the other hand, it was shown that for pitches from decant oil it is possible to isolate up to 65% or more of the mesophase with a softening point not higher than 250 degrees C.