Thermogravimetric Study of Ozone-Modified Coal Tar

Thermogravimetric analysis is used for preliminary assessment of how ozonation affects the yield of coal tar factions in distillation. Since the distillation temperature of light fractions matches the main peak of gas liberation in coal tar pyrolysis, the yield of tar fractions may be indirectly assessed by means of the intervals corresponding to the boiling points of standard tar fractions: <170°C, light; 170–210°C, phenol; 210–230°C, naphthalene; 230–300°C, absorbing fraction; 300–360°C, anthracene; and 360–1000°C, pitch. Treating tar with ozone in the absence of solvents does not significantly change the yield of the fractions. By contrast, ozonation of coal tar in the presence of benzene and chloroform lowers the yield of fractions boiling below 300°C and significantly increases the mass loss in the temperature ranges corresponding to the anthracene fraction and pitch.