Study On De-intercalation Of The Intercalated Potassium In The Preparation Of Activated Carbons By Alkali Activation

High specific surface area activated carbon is an excellent material for the preparation of supercapacitor,catalyst,catalyst carrier and fuel gas storage medium because of its rich pore structure and large adsorption capacity.Activating petroleum coke by KOH has been a hot research topic in the preparation of high specific surface area activated carbon.The activation mechanisms by KOH have been widely studied.During the activation with KOH,metallic potassium is inevitably formed.The potassium might intercalate in between the hexagonal carbon layers of the crystallite of activated carbons?ACs?and so that plays an important role in porosity development.We should know that not only the intercalation of potassium but also the de-intercalation of potassium-graphite intercalation compounds?K-GICs?make contributions to the porosity development of ACs.The de-intercalation of potassium would not only improve the porosity development,but also provide convenience for doping of ACs,and so that to modify the properties of ACs to match different applications.In this study,ACs were prepared from petroleum coke?PC?with KOH as activation agent,and after the furnace cooled down to a desired temperature,H₂S?H₂O?HCl entrained in nitrogen flow was introduced into the reactor.The effects of H₂S on the porosity development of the resultant ACs at different temperature were investigated by using BET method;and the effects of H₂S on the surface properties of the resultant ACs were investigated by using the elemental analysis,FTIR analysis,and Boehm titration;and with XPS analysis,XRD analysis,the paper proposed the mechanism of intercalation and de-intercalation process.The experimental results show that the total pore volume?V_t?and micropore volume(V_micro)of activated carbon are reduced after H₂S introduction,and the specific surface area(S_BET)decreases with the increase of temperature.The rate of mesopore increased in varying degrees.Comparing the effects of H₂S,H₂O and HCl on the de-intercalation results,it is found that compared to HCl and H₂S,the reaction atmosphere with H₂O is relatively mild and has less influence on the internal crystal structure of activated carbon;HCl and H₂S have strong acidity and corrosiveness,not only reaction with the intercalated potassium,but also changing the inner and outer surface pore structure of activated carbon.The spacing distance between layers became shorter.the number of micropores decreased,expanding into the mesopores and macropores.