A Combined FTIR and Textural Study of the Oxidation of a Bituminous Coal

A FTIR study to detect the chemical modifications involved during the oxidation of a Spanish coal from the Central Asturian Basin (Spain) has been carried out. The coal was oxidized at 473 K for periods of 3, 7, 14 and 42 days, and at 543 K for 1, 2, 3, 4 and 14 days. Results show that at each temperature there was an increase in oxygenated functions (carboxyls, esters, anhydrides, ethers) and a gradual decrease in aliphatic and aromatic structure. There are remarcable differences at the two temperatures. Intermediate states of oxidation, less condensated structures and an appreciable proportion of the aliphatic C-H groups are predominant in coal samples oxidized at 473 K. When oxidation is carried out at 543 K, more oxidized forms, a more marked process of decarboxylation and more condensated structures appear, also aliphatic groups disappears almost totally. Chemical analysis and textural properties of each oxidized coal sample have been carried out, and a correlation between chemical changes detected by FTIR and textural properties has been attempted.