THE OXIDATION OF AN ASTURIAN BITUMINOUS COAL IN AIR AND ITS INFLUENCE ON SUBSEQUENT ACTIVATION BY STEAM

It is shown that the oxidation of an Asturian bituminous coal by air, at 150 degrees and 270 degrees C, has a considerable influence on the microporous structure of the carbon obtained by subsequent carbonization and steam activation to 50% burn-off. The direct activation of the coal leads to an open micropore system of 0.2 cm(3)/g, with an average pore size near 0.8 nm. On the other hand, much larger systems of micropores can be obtained in the final products, depending on the temperature of pretreatment in air. The oxidation at 270 degrees C eventually leads to supermicropores (W-0 = 0.4 cm(3)/g) and to a small system of narrow micropores near 0.3-0.5 nm. Molecular sieving experiments indicate that these micropores are part of the constrictions leading into 50-60% of the larger pores.