Powdered activated carbons and activated carbon fibers for methane storage:: A comparative study

During this study different raw materials, activating agents, and preparation variables were used to compare the behavior of carbon materials with different morphologies in methane storage applications. Two different types of carbon materials have been prepared: W chemically activated carbons prepared from an anthracite and a bituminous coal using KOH as activating agent, and (ii) physically activated carbon fibers prepared from petroleum pitch and coal tar pitch-based carbon fibers, by activation with CO2 and steam. Both type of materials have been prepared in order to cover a wide range of surface area. The effects of different properties of the adsorbents (porous texture, packing density, and pore size distribution) in their performance in methane storage applications (methane uptake and delivery) were analyzed. The comparison of both types of materials (powder and carbon fibers) has shown that activated carbon fibers have the advantage of a higher packing density than powdered activated carbons. On the other hand, the chemically activated carbons have the advantage of higher methane adsorption capacity than activated carbon fibers with similar micropore volumes, due to their narrower micropore size distribution. During the present work an adsorbent with a volumetric methane uptake as high as 165 V/V and another sample with a delivery as high as 145 V/V were produced.