[Compositions and structure characterizations of coal tar refined soft pitch].
High temperature coal tar was used as raw materials, and was distilled to 280 degrees C for getting coal tar soft pitch. Then refined soft pitch was obtained by solvent extracting and subsequent settlement method. Its soft point was 32 degrees C; the group compositions consisted of 53.67% heptane soluble, 39.47% heptane insoluble but toluene soluble, 6.86% toluene insoluble and 0.06% quinoline insoluble. The relative average molecular weight was about 292. Its average molecular formula was C22.22 H16.32 N0.12 S0.06 O0.33; the total content of heteroatom was less than 1. IR analytic results showed that its heteroatom O existed in the R-O-R and Ar-O-R structure; its heteroatom N existed in the R-NH-R and -N=, with the latter being primary. Its average structure was obtained by improved Brown-Lander model: five-membered condensed rings. UV analysis indicated that the majority was linear arrangement, and the minority was surface arrangement; namely, the chemical structure of the samples was mainly the cata-condensed structure, while the minority was peri-condensation.