Abstract
Anthracite activated carbons are proper adsorbents for methane storage. In this study, Iranian local anthracite was activated using two commonly used chemicals (sodium hydroxide and potassium hydroxide) at similar conditions and their products are compared with regard to various properties in order to find the optimal operating parameters such as temperature, chemical ratio and pyrolysis time for producing ACs with high surface area. Three activation temperatures (670, 730 and 790 °C), three chemical-to-coal ratios (2, 2.5 and 3) and two pyrolysis times (1 and 2 hours) were studied in each carbon series (NaOH and KOH). Accordingly, the pore structures of Activated carbon (ACs) were investigated accurately based on adsorption isotherms of nitrogen as well as density functional theory. In addition, their methane storage capacities were also measured and discussed. Specific volumes (microporosity and mesoporosity) of products were also calculated. The KOH ACs had higher micropore volumes, whereas NaOH ACs had relatively higher densities. The highest methane storage was obtained by a KOH AC sample with 3:1 chemical-to-coal ratio (R), activated at 730 °C for 1 hour (AK37301). The stored and delivered methane for this sample were 176 and 158 vol/vol, respectively.