Preparation And Applied Research Of Acticated Cabon From Xinjiang Petroleum Coke

As an excellent absorbent, Activated Carbon(AC) with developed pore structure and huge specific surface has been widely used in the area of environmental protection, industry, national defense, medical health and ect, furthermore, it has potential applications on the supercapacitor, gas storage, gas separation and catalyst support. With the expansion and specialization of the application of AC, researches on preparation of AC towards low cost, high adsorption capacity and controllability. Petroleum coke, one byproduct in the process of oil refining, has been regarded as a good raw material to prepare AC because of its'nominalprice, high fixed carbon content and low ash content. Through optimizing the preparation conditions according to the activation mechanism and reducing KOH/Coke ratio, making pore structure and specific surface controllable was a problem need to be resolved. In this text, taking petroleum coke of Karamay Refinery as precursor and KOH as activating agent, high specific surface activated carbon was prepared. The effection of different preparation conditions on pore size distribution and specific surface area of AC was investigated systematically. The electrochemical property and gas storage performance of the as-synthesized AC under different activation conditions were also investigated. The main contents and results are as follows:1. The effect of KOH/Coke ratio, temperature and time of activation on the properties of AC were investigated. It was found that pore size distribution and specific surface area of AC affected by KOH/Coke ratio greater. AC with developed micro porous structure or mesoporous structure can be synthesized by adjusting KOH/Coke ratio. When KOH/Coke ratio is 6:1, activation temperature is 800℃, activation time is 1h,an AC with specific surface area as high as 3587 m²/g and the total volume 2.02 cm³/g could be prepared at optimum conditions.2. The TG cures and exhaust gas in the activation process were analyzed by simultaneous TG-MS, the role of each component in the activation reaction as follows: Before 600℃, KOH directly reacted with oxygen groups and alkyl groups on the surface of petroleum coke and generated a lot of H₂O, a small amount of H₂ and CH₄; Around 800℃,the K₂CO₃ and K₂O generated from KOH, continued react with carbon and then generated CO₂ and CO; The generated K vapor intercalate into the lamellae of the carbon and formed intercalation compounds, which further promote the formation of the porous structure. The TG curves at different heating rates were analyzed by thermal dynamics software, then proposed reaction model of the activation reaction and calculated kinetic triplet.3. The influence of pre-oxidation of the PC with the different concentrations of HNO₃, HClO₄, H₂O₂ on pore size distribution and specific surface area of the produced AC was investigated. The results showed that introduction of the surface oxygen groups by the pre-oxidation can increase the activation reaction and reduce the KOH/Coke ratio, the effect of pre-oxidation varies in the order of HNO₃>HClO₄>H₂O₂. An AC with a surface area 2332 m²/g and the total volume 0.97cm³/g was prepared from the coke oxidized by 3mol/L HNO₃ with a 2:1 KOH/Coke ratio, equaling to a 3:1 KOH/Coke ratio.4. The electrochemical performance of the produced AC as anode materials for lithium-ion batteries were investigated, and compared with the electrochemical performance of heated-treated petroleum coke. The electrochemical measurements showed that: the discharge capacity of the produced AC was advanced remarkably with the increasing of specific surface area. The as-synthesized AC with a surface area 3587 m²/g showed a high initial discharge capacity of 1546 mAh g^-1 at 0.5 C, and the discharge capacity is 625.1mAh g^-1 after 50 cycles, which is still larger than the theoretical capacities of graphite. At low current density(≤1C), the electrochemistry properties of AC with high specific surface area has surpassed heated-treated petroleum coke, but nearly at high current density.5. H₂ and CO₂ storage performance of the as-synthesized AC under different KOH/Coke ratio were investigated. It showed that, H₂ adsorption on AC increased with the increase of the specific surface area of AC, and maximum adsorption capacity could reach 5.04wt% at 77K and 1MPa. CO₂ adsorption on AC showed in linear progression with the rising of pressure, and the maximum adsorption capacity was 3.65 wt% at 273K and 0.1MPa.