Adsorption of methane into ZnCl2-activated carbon derived discs

Binderless activated carbon discs for methane adsorption have been prepared by impregnation of olive stones with solutions of ZnCl2, compacting under pressure at 150 and 300degreesC and heat treatment at 500degreesC under a flow of nitrogen. The porosity development along the activation process is expected for this precursor; activated carbons with a very small volume of meso- and macropores and a large volume of micropores are obtained when the impregnation ratio is intermediate, X-Zn = 0.30g/g. Since compacting under pressure means a low interparticle space, the disc volume (above 1.2cm(3)/g) is almost equally distributed between micropores and the carbon skeleton. The methane capacity at 3.4MPa is in the range of 100V/V. Two discs were further activated by reaction under a flow of carbon dioxide. Although such activation implies a decrease in the bulk density because there is an increase in interparticle space (specially when the original disc is very dense), there is a net increase in the volume of micropores, the methane capacity increasing around 10%. (C) 2004 Elsevier Inc. All rights reserved.