Using granular activated carbon prepared from oil palm shell by ZnCl ₂ and physical activation for methane adsorption

Granular activated carbons for methane adsorption have been prepared by impregnation of oil palm shell with various solutions of ZnCl₂ followed by heat treatment at 500 °C under a flow of nitrogen. For this precursor, large micropore volume of micropores (with a very small volume of mesopores and macropores) was obtained with intermediate ZnCl₂ mass ratio. Methane capacity at 800 mmHg was in the range of 10-12 cm³/g. All the samples were further activated by reaction under a flow of carbon dioxide. Although such activation resulted in a decrease in the BET surface area, average pore width, micropore and pore volume (except very low impregnation ratio, X_Zn = 0.15 g/g), however, there was a 100% net increase in the methane capacity.