Influence of chemical modification of anthracite on the porosity of the resulting activated carbons

Activated carbons in a wide range of porosity (from essentially microporous to essentially mesoporous) have been prepared from anthracite by the combination of a chemical treatment with HClO4 or Mg(ClO4)(2) and a physical activation with CO2 at 850 degreesC. The main effects of the chemical treatment are a modification of anthracite microstructure by insertion and oxidation. The extent of these two reactions was found to be related to the nature of the chemical agents, the treatment time and temperature, and the textural properties of anthracite. As a consequence, the pretreatment of anthracite causes a noticeable reduction of the activation time and a change of the final pore size distribution. The influence of chemical treatment parameters has been analysed by means of XPS, FTIR, TGA, mass spectrometry, elemental analysis and gas adsorption techniques. The optimal conditions for producing activated carbons from chemically modified anthracites were identified. Step by step increasing of the temperature of anthracite treatment by HClO4 up to 160 degreesC seems to be the best way to obtain a precursor of highly activated carbon with well-balanced micro and meso porosity. (C) 2002 Published by Elsevier Science Ltd.