A small angle X-ray scattering study on the porosity of anthracites

SAXS technique is applied on anthracites to study their heterogeneous microtexture and the mechanism of partial graphitization during a thermal treatment up to 2800 degrees C. The effects of heat treatment on the porosity were observed at 1600 degrees C and 2800 degrees C and compared with homogeneous microtextures of mesoporous saccharose-based coke and lamellar anthracene-based coke. The main feature observed on raw anthracites, displaying the least degree of natural maturation and the largest isotropic distribution of aromatic units, is the occurrence of a characteristic distance of 20 Angstrom. After a HTT of 1600 degrees C, the porosity of anthracites is close to 10-12%, carbon domains still being weakly organized, particularly on raw anthracites with the higher isotropic microtexture. Discrepancies resulting from the graphitization degree reached at 2800 degrees C were shown using the porosity and the mean length of chord in the matter. The porosity varies respectively from 19%, corresponding to a mean length chord of 97 Angstrom for least graphitized anthracites, to 10% and a mean length chord of 235 Angstrom for the most graphitized one. (C) 2000 Elsevier Science Ltd. All rights reserved.