Influence of granular carbons on pitch properties

This paper deals with the study of the variation of properties of four pitches (a commercial impregnating coal tar pitch, an air-blown and two thermally treated pitches) when mixed with four granular carbons (anthracite, graphite, green petroleum coke and foundry coke). As a first step, optical microscopy was used to determine the distribution of the pitch among the granular carbons. The anthracite seems to attract the primary quinoline insolubles present in the commercial and thermally treated pitches. This allows the mesophase spheres to coalesce at unusually low temperatures during the mixing process. In general, the toluene insoluble content of the pitch showed a significant increase after mixing with the granular carbons. This is an indication of the interactions between the different granular carbons and some compounds present in the pitches. Analytical techniques like size exclusion chromatography and differential scanning calorimetric analysis were used in order to obtain information about the characteristics of the components of the pitches that interact with the different granular carbons and their effect on pitch properties. Graphite seems to interact preferentially with the larger molecules whereas the green petroleum coke acts on a wider molecular range.