PREPARATION OF ACTIVATED CARBONS FROM BITUMINOUS COALS WITH CO2 ACTIVATION .1. EFFECTS OF OXYGEN-CONTENT IN RAW COALS

Activated carbons were prepared from three Australian bituminous coals in this study. The preparation process consisted of carbonization fol lowed by activation in CO2. Experimental results reveal that the oxyge n content of the coals has a great influence on the behavior during pr eparation and on the properties of the products. The coal with a highe r O/C atomic ratio has a lower peak temperature for volatile evolution during carbonization and is able to produce a char with a higher surf ace area. The reactivity in CO2, the surface area, and the pore volume of the resulting activated carbon are all increasing functions of the O/C ratio' of the coal precursors. An SEM study shows that at high bu rn-off levels a higher portion of gasification occurs at the exterior surface of the carbon from the coal with a lower O/C ratio, indicating that the diffusion resistance may be stronger for this carbon. For th e same coal precursor, the average pore diameter of the activated carb on increases as the temperature for activation is increased in the ran ge of 800-900 degrees C.