NaOH activation of anthracites: effect of temperature on pore textures and methane storage ability

The main purpose of this work was to prepare various active carbons from the same precursor at various activation temperatures, and investigate both porosity development and corresponding methane storage capacities. An anthracite was thus chemically activated with sodium hydroxide under nitrogen flow at temperatures ranging from 600 to 830 degreesC, with a constant mass ratio: hydroxide/anthracite = 3. The pore textures of the corresponding activated carbons were investigated using the adsorption isotherms of four probe molecules characterised by their increasing molecular diameters, namely CO2, N-2, C6H6 and CCl4. The changes occurring in each kind of pores were discussed and put in relation with the activation temperature. The specific volumes of different micro- and mesopore families were measured and discussed. Depending on the temperature range, two different activation mechanisms were evidenced. Methane storage isotherms at 20 degreesC and up to 3.5 MPa were measured for the investigated materials. Linear correlations between various textural parameters and methane storage capacities were given. Additionally, a number of results previously reported in the literature were confirmed by the present work. (C) 2004 Elsevier Ltd. All rights reserved.