IN-SITU EXAMINATION OF COAL MACERALS OXIDATION BY MICRO-FT-IR SPECTROSCOPY

Two heterogeneous coals, from the Mahakam delta (HY 158) and the Campi ne basin (SP 1), have been selected for an in situ study of individual maceral oxidation. HY 158 is vintrinite rich (80%) but also contains resinite and bituminite, while SP 1 is a cannel coal composed of spore s, vitrinite and inertinite. Doubly-polished thin-sections have been p repared and photographed in order to select the appropriate individual maceral areas. The thin-sections were oxidized at 140-degrees-C in a ventilated oven for 1 to 384 h. Between each oxidation step the select ed areas were analysed by Fourier transform micro-infrared spectroscop y (micro-FT-i.r.). Aliphatic CH consumption, carbonyl, carboxyl and et her content increases are observed. However, results indicate that mac erals behave differently when submitted to increasing oxidation: (1) e xtents and rates of oxidative alteration strongly depend on the nature of the maceral; (2) two different vitrinites can exhibit contrasting behaviour; (3) slight differences in the chemical composition of the u noxidized macerals can induce significant chemical variations during t he oxidation process. Comparison with global FT-i.r. data obtained on powdered and oxidized parent coal has been carried out (HY 158) and al though there are similarities, variation in the extent of the oxidativ e alteration occurs.