Thermal Conversion of Coal-Tar Pitch in the Presence of Silicon Compounds

The effect of SiO2 and polycarbosilane (PCS) additives on the thermal degradation of coal-tar pitch at temperatures to 900 degrees C was studied by thermogravimetric analysis, differential thermal analysis, mass-spectrometric analysis, IR spectroscopy, and electron microscopy. It was found that, in the presence of the test additives, the character of release and the quantitative composition of volatile degradation products changed, the degree of aromaticity of the carbon residue decreased, and the concentration of oxygen-containing groups in this residue increased. In the case of the PCS additive, the combined thermal conversion of both of the components occurred. In this case, the contribution of structurization processes increased to cause a nonadditive increase in the yield of solid residue. Silicon mainly occurred as organosilicon fragments with Si-C and Si-O-C bonds, an oxycarbide, and, probably, silicon carbide. In the case of the SiO2 additive, oxidation processes were enhanced; the yield of carbon somewhat decreased, and siloxane groups were present in the solid residue.