Preparation Of Activated Carbon From Petroleum Coke By KOH Activation In The Presence Of Hydrogen And The Technology For The Continuous Activation

Activated carbons (AC) produced by KOH activation are widely used in fuel gas separation, gas storage, catalysis reaction, electric double-layer capacitor (EDLC) materials and various chemical processes due to their developed micropore structure and larger pore volume. It is well known that petroleum coke (PC) is a good precursor for preparing high surface area AC because of its abundant resource, high carbon content, low volatile and ash content. However, PC is difficult to be activated due to the stable micro-graphitic structure. Generally, high KOH/PC ratio is needed to prepare AC from PC, which brings many problems, such as high KOH consumption, high pollution, high cost, equipment corrosion, hidden danger, and so on. These problems restrict the exploration and application of PC-based high surface area activated carbons. In domestic, the research on the production of AC from PC by the KOH activation is just in the batch production with the small scale device. This will cause the low production efficiency and restrict its large scale production. Therefore, how to explore a process technology with low KOH consumption and continuous equipment for the production of AC with high performance is the emphasis for further research. In this dissertation, investigations were conducted as follows:AC was prepared from a green petroleum coke (PC) from SINOPEC Liaoyang Petrochemical Company and KOH as activating agent in the presence of Ho. The horizontal tube furnace was used for the activation. The effects of preparation variables including KOH/PC ratio, activation temperature, activation time, content of H2in the carrier gas and particle size of the PC on the porosity development of the AC were investigated. All the variables had an important influence on the performance of the AC. At the KOH/coke ratio of2:1, activation temperature780℃and activation time60min, AC with the specific surface area of2477m2/g and pore volume of1.10cm3/g was prepared in the presence of30%H2. The surface area and pore volume of the AC increased by500m2/g and0.25cm3/g, respectively, compared with that of AC prepared in the N2atmosphere.The effects of H2on the carbonization of PC were investigated. The presence of H2is beneficial for removal of the surface heteroatom groups of the PC during the carbonization process, which caused the carbonized samples had a lower content of nitrogen, sulfur and oxygen. Meanwhile, additional-CH-and-CH2-species were formed due to the chemisorption of H2on the nascent sites of the PC created by the removal of the surface heteroatom groups.The effects of H2on KOH activation of petroleum coke were systematically investigated by analyzing the evolution rate of H2, evolution of water, production of metallic K and element content of AC. The reaction of H2with the surface groups of PC caused the reduction of H2content in the sweep and the increase in the production of water. The formed-CH-and-CH2-species could act as ’active sites’ to participate in the activation reaction. The increase in the quantity of’active sites’is beneficial to the further activation reaction. And the formation of metallic K could enhance the activation reaction.The PC (deashed with hydrochloride acid and hydrofluoric acid), graphite and other carbon materials (with some surface groups) were adopted as the raw materials for the activation under N2and N2+H2atmosphere. The result showed that the ash in the PC almost has no effect on the KOH activation of PC. The introduction of H2in the carrier gas almost has no effect on the porosity development of AC prepared from graphite. But as the other carbon materials were used as raw material, the introduction of H2is beneficial for the porosity development of the AC. The water produced by the interaction of H2and suface oxygen groups of PC had no evident effect on the porosity development of the resultant activated carbon.AC prepared from PC was used as electric double-layer capacitor (EDLC) materials. At the KOH/coke ratio of3:1, activation temperature780℃and activation time60min AC with specific surface area of2824m7g and pore volume of1.56cm/g was prepared in the presence of30%H2. The specific surface area, total pore volume and mesopore volume of the AC increased by400m2/g,0.40cm3/g and0.25cm3/g, respectively, compared with that of AC prepared in the N2atmosphere. At the investigated range of scanning rate, the gravimetric specific capacitance of the electric double-layer capacitor made from the AC prepared under H2+N2is higher than that prepared in the N2atmosphere.Based on the characteristic of KOH activation, the continuous activation system was constructed which included the dehydration system, continuous activation system and metallic potassium convertion system. And the continuous activation device was designed, constructed and adjusted. The performance of AC prepared with the activation device is close to that prepared with horizontal pipe reactor. Porosity characterization of AC from different batches showed that the AC prepared with the activation device has a good stability.