EFFECTS OF SELECTIVE CHEMICAL MODIFICATION OF COAL ON TAR AND GAS-FORMATION DURING PYROLYSIS

Vitrain from Debiensko bituminous coal was modified by selective chemi cal reaction to reveal particular structural characteristics of organi c matter responsible for the improved or worsened conversion during th e solubilization of coal by methanol-NaOH treatment. The selective rea ctions were: alkylating and non-alkylating reduction according to Ster nberg, performic acid oxidation, thermal decarboxylation of the oxidiz ed vitrain, LiAlH4 reduction of the oxidized vitrain, and O-methylatio n of residual hydroxyl groups. The original vitrain and the products o f the modification reactions were pyrolysed in a stream of helium at a tmospheric pressure and the volatile compounds were continuously detec ted during thermal programming, using flame ionization detection or ma ss spectrometry. The compounds detected were: tar and light oils, CO2, CO, SO2, H2S, CH4, H-2 and N2. The results are in agreement with the expected changes in chemical structure. A number of coal structural fe atures are revealed by detailed examination of the gas profiles. Oil a nd gas evolution correlate well with infrared spectroscopy and sequent ial solvent extraction of the modified samples. The higher oil yield a nd the lower yields of H-2 and N2 can be attributed to the suppression of the regressive effect of the oxygen groups and to the addition of hydrogen centres.