Analysis of coal tar pitch: relations between thermal behaviour and composition

Abstract

This paper discusses the influence of pitch composition on its thermal behaviour. The value of the approach consisting in the characterization of these materials by analysis of their volatile fraction is demonstrated. The pyrolysis of nine coal tar pitches was studied by thermogravimetric analysis (t.g.a.) and derivative thermogravimetry (d.t.g.). The coke yield was closely related to both the rate of weight loss and the temperatures at which the d.t.g. curve reached maxima. To obtain information about the influence of the structures present in pitches on their thermal behaviour, the composition of the volatile fraction (evaluated by gas chromatography) was considered. The degree of condensation and the relative proportions of the different kinds of polycyclic aromatic hydrocarbons in this fraction were related to important thermal parameters deduced through t.g.a. and d.t.g. High coke yields are associated with a highly condensed volatile fraction in which alternant peri-condensed polycyclic aromatic hydrocarbons predominate over non-alternant systems.