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

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 nal 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 the opposite effect on the capacity of the samples activated by zinc chloride. 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 an impregnation ratio of 0.7 and, subsequently, physically activated by carbon dioxide. It has a BET surface area of 1479 m2/g, an average pore diameter of 4.2 nm, the total pore volume of 0.84 cm3/g, and the methane adsorption capacity of 159 cm3/g. The sample shows high stability during successive adsorption/desorption cycles experiment.