Effect of Pore Size on Adsorption of Hydrocarbons in Phenolic-based Activated Carbon Fibers

The combined effect of pore size and pore volume on the equilibrium adsorption capacity and the adsorption kinetics for a series of normal alkanes is determined. The selected adsorbents, activated carbon fibers (ACFs) and air activated phenolic fibers (AAPFs), possess a range of micropore sizes and have been thoroughly characterized in past work. For the normal alkane series, the lower surface area (smaller pore size) adsorbents demonstrate higher adsorption capacities for low boiling point alkanes and for adsorbing molecules at low concentrations. For higher boiling point alkanes and at higher concentrations, the adsorption capacity is greater for higher surface area materials (larger pore size) due to increasing pore volumes. This data was modeled using the DR equation to develop a predictive capability for adsorption based on boiling point and micropore size. For the full range of gas concentrations, the average initial mass rates of adsorption increase as the average pore size increases.