ANALYSIS OF COAL-TAR PITCH - RELATIONS BETWEEN THERMAL-BEHAVIOR AND COMPOSITION

This paper discusses the influence of pitch composition on its thermal behaviour. The value of the approach consisting in the characterizati on of these materials by analysis of their volatile fraction is demons trated. The pyrolysis of nine coal tar pitches was studied by thermogr avimetric 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 o n their thermal behaviour, the composition of the volatile fraction (e valuated by gas chromatography) was considered. The degree of condensa tion and the relative proportions of the different kinds of polycyclic aromatic hydrocarbons in this fraction were related to important ther mal parameters deduced through t.g.a. and d.t.g. High coke yields are associated with a highly condensed volatile fraction in which alternan t peri-condensed polycyclic aromatic hydrocarbons predominate over non -alternant systems. Copyright (C) 1996 Elsevier Science Ltd.