Przemysl Chemiczny, Vol.85, No.6, 423-426, 2006
The effect of oxidation of flame coal on the microporous structure of carbon dioxide-activated chars
A flame coal was oxidized in air at 250 degrees C for 40 h, carbonized (5 degrees C/min in Ar, up to 850 degrees C) and activated with CO 2 at 850 degrees C to achieve burn-off levels of 5-25%. The porous structure of the activated chars was evaluated via sorption of CO2 and org. vapors of rising mol. diams. (CH2Cl2, C6H6, C6H12 and CCl4) at 25 degrees C. Oxidn. of the coal resulted in a reduced vol. of submicropores (< 0.4 nm), a distinctly increased vol. of micropores (0.4-2 nm), and a slight development of mesopore (2-50 nm) vol. in activated chars. In chars activated to < 10% burn-off levels, oxidn. was particularly conducive to the creation of a narrow micropore size distribution, close to 0.4-0.5 nm, and to the mol. sieve properties within the above limits of micropore sizes.