Adsorbed Natural Gas Storage with Activated Carbons Made from Illinois Coals and Scrap Tires

Activated carbons for natural gas storage were produced from Illinois bituminous coals (IBC-102 and IBC-106) and scrap tires by physical activation with steam or CO2 and by chemical activation with KOH, H3PO4, or ZnCl2. The products were characterized for N2-BET area, micropore volume, bulk density, pore size distribution, and volumetric methane storage capacity (V m/V s). V m/V s values for Illinois coal-derived carbons ranged from 54 to 83 cm3/cm3, which are 35−55% of a target value of 150 cm3/cm3. Both granular and pelletized carbons made with preoxidized Illinois coal gave higher micropore volumes and larger V m/V s values than those made without preoxidation. This confirmed that preoxidation is a desirable step in the production of carbons from caking materials. Pelletization of preoxidized IBC-106 coal, followed by steam activation, resulted in the highest V m/V s value. With roughly the same micropore volume, pelletization alone increased V m/V s of coal carbon by 10%. Tire-derived carbons had V m/V s values ranging from 44 to 53 cm3/cm3, lower than those of coal carbons due to their lower bulk densities. Pelletization of the tire carbons increased bulk density up to 160%. However, this increase was offset by a decrease in micropore volume of the pelletized materials, presumably due to the pellet binder. As a result, V m/V s values were about the same for granular and pelletized tire carbons. Compared with coal carbons, tire carbons had a higher percentage of mesopores and macropores.