Activated nanoporous carbon from walnut shell as a promising adsorbent for methane storage in adsorbed natural gas technology

Abstract Activated carbon from walnut shell is studied for methane storage in this research. The samples are ‎synthesized by zinc chloride and phosphoric acid, as activating agents. The effect of physical ‎activation, after chemical activation steps, on the final structure of the samples and their total methane ‎storage is examined. The results show that physical activation has an improving effect on the total ‎capacity of the samples activated by phosphoric acid, however; it has a reverse effect on the ‎capacity of zinc chloride activated ones. The experimental data show that the best capacity is ‎obtained at impregnation ratios of 0.7 and 1.2 in the case of phosphoric acid and zinc chloride ‎activated samples, respectively. The best sample is the one activated by phosphoric acid with ‎impregnation ratio of 0.7 and subsequently physically activated by carbon dioxide. It has the BET ‎surface area of 1479 m2/g, average pore diameter of 4.2 nm, total pore volume of 0.84 cm3/g and ‎methane adsorption capacity of 159 cm3/g. The sample shows high stability during successive ‎adsorption/desorption cycles experiment. ‎