EFFECTS OF METHANOL-NAOH TREATMENT OF COAL ON TAR AND GAS-FORMATION DURING PYROLYSIS

Vitrain from a bituminous coal was modified by selective chemical reac tion to reveal particular structural characteristics of the organic ma tter responsible for the change in conversion during solubilization by methanol-NaOH treatment (M treatment). The selective reactions were a lkylating and non-alkylating reduction according to Sternberg, perform ic acid oxidation, thermal decarboxylation of the oxidized vitrain, Li AlH4 reduction of the oxidized vitrain and O-methylation of the residu al hydroxyl groups. The products of M treatment were pyrolysed in a st ream of helium at atmospheric pressure, and the volatile compounds wer e continuously detected by flame ionization or mass spectrometry. The changes in structure and reactivity during M treatment were assessed b y comparing gas evolution during programmed pyrolysis of the M product with that of the initial vitrain and its modified by-products. The M treatment strongly increased the pyrolytic conversion, and correspondi ngly reduced the formation of molecular hydrogen during secondary pyro lysis. The methylation of aromatic systems in the coal by M treatment is a main component of this process. The oxidized vitrain and its oxid ized products show the highest conversion, indicating the critical rol e of hydrogenation in bond-breaking and in prevention of regressive re actions during M treatment. Pre-oxidation and LiAlH4 reduction enhance denitrogenation of the coal during M treatment and subsequent pyrolys is.