Preparation And Preliminary Application Of High Surface Area Activated Carbon

HSAAC (high surface area activated carbon) is widely used in fuel gas storage, gas separation, catalysis and various chemical processes. Cokes are by-products of the petroleum product. It is well-known that PC (petroleum coke) is a good precursor for preparing high surface area AC (activated carbon) because of its abundant resources, low price, high carbon content, low volatile and ash content. However, PC is difficult to be activated due to its stable micrographitic structure. A large amount of KOH is needed to prepare AC, which brings many problems, such as high product cost and environment pollution. Therefore, how to optimize the technical conditions and lower KOH/coke ratio is of great value for further research.AC is prepared from a commercial PC from CNPC Liaohe Petrochemical Company as the precursor and KOH for activation, the effect of different preparation conditions on the properties of AC was investigated by using orthogonal design and single factor analysis. It has been found that the PC is a good precursor for preparing AC with a high iodine adsorption value. Meanwhile, the properties of AC are affected by activation temperature, KOH/coke ratio, activation time and their interactions.The influence of PC pre-modification with H₂O₂ and HClO₄ on the surface properties of AC was analyzed. The results showed that the alkyl groups of PC disappeared, and the oxygen functionalities were formed by pre-modification. And the addition of oxygen to the graphitic microcrystallines of the precursors slightly widens the interlayer spacing. Also, it leads to an increase in the reactivity of the PC in chemical activation, which results in an increase in the BET surface area. Based on the above results, it can be indicated that the surface oxygen functionalities of the precursor can be acted as 'active site', which play an important role in activation. Therefore, an AC with a surface area as high as 2336 m²g^-1 was prepared from the coke oxidized by 15%H₂O₂ solution with a 3:1 KOH/Coke ratio.The high surface area activated carbon was used as the adsorbent for methane storage, and effects of BET surface area and iodine adsorption value on the adsorptive capacity of adsorbents was investigated. Results indicated that The AC with high surface area and pore size distribution between 1～2nm, was a good adsorbent for methane storage compared to other two samples from Hebei and Institute of Coal Chemistry of Chinese Academy of Science. The volume adsorption capacity was 95V/V at room temperature and the pressure of 3.5MPa. It was found that BET surface area and pore size distribution played an important role in the storage of methane.