Production and adsorption characteristics of MAXSORB: High-surface-area active carbon

High-surface-area (over 3000 m2 g−1) active carbon has been developed with an extremely large adsorption capacity. Various kinds of petroleum coke were mixed with an excess amount of KOH and dehydrated at 400°C, followed by activation at 600–900°C in an inert atmosphere. The remaining KOH was removed by washing with water after the activation. Pore analysis indicated that this active carbon has a large portion of mesopores (1.0–1.5 ml g−1) with radii between 10 and 20 Å, whereas micropores are as numerous as in conventional steam activated carbon (0.5 ml g−1). Since considerable amounts of K2CO3 and hydrogen were formed, the majority of the carbon consumption was due to the transformation of K2O into K2CO3 by CO2. Potassium metal was also formed from the hydroxide by dehydration and reduction by hydrogen or carbon. Reversible adsorption of gasoline vapour, and isotherms of methylene blue and iodine in solution were obtained. Regardless of the kind of adsorbent tested, the adsorption capacity increased proportionally to the BET surface area. The fact that the surface area exceeds the geometric maximum was explained by introducing the concept of associated adsorption. This product is now commercially available from our company under the brand name of MAXSORB.