Preparation Of Coal-based Mesophase Semi-coke And Research On Its Application In Supercapacitor Electrode Materials

Coal dense medium component from the coal all-components group separation served as the material to prepare mesophase semi-coke.The effects of carbonization temperature,holding time,heating rate and briquetting pressure on mesophase semi-coke and generation process of mesophase semi-coke were investigated.The functional group structure and crystallite structure of the mesophase semi-coke were analyzed.The mechanism of formation of mesophase semi-coke from dense medium component was discussed.Active mesophase semi-coke which was prepared by KOH aactivation method was used as electrode to assemble a supercapacitor,and the electrochemical properties were characterized.The results show that the increase of temperature intensifies the reaction of pyrolysis and polycondensation,which is conducive to the formation of mesophase with wide area streamline structure.When the temperature is higher,the reaction is too violent,not conducive to the development of mesophase;The extension of holding time deepens the reaction process,which is conducive to the evolution of the streamline structure of mesophase semi-coke.When the heating rate is too slow or too fast is not conducive to the orderly development of mesophase,the optical heating rate to form the wide area streamline mesophase semi-coke is 4 ? /min.The briquetting pressure of raw materials mainly affects the development of mesophase by changing the particle gap,increasing the pressure will affect the thermal efficiency,small molecules escape and the guidance of inert gas,which is not conducive to the orderly development of mesophase.The optimal conditions to generate mesophase spherules and streamline mesophase semi-coke are 450 oC,4oC/min and bulk feed.Under the conditions above,the evolutionary process of mesophase is mesophase spherules,small wide area,medium streamline,wide area streamline(the coarse),wide area streamline(the fine).The mechanism of mesophase semi-coke formation is the nanoparticles with the size of 3~5 nm transformed into plane,aggregation of the plane molecules aggregate and stack to layer integrated,the molecular layer integrated interpenetrate to based unclears,based unclears integrate to mesophase spherules,integrating and growth of spherules,The spherules disintegrate to small wide area mesophase,the mesophase develop to wide area streamline by thermal condensation and airflow shear.The activated mesophase semi-coke prepared from different optical appearance of mesophase semi-coke and a mild KOH activation procedure possessed high surface area with 2000 m2/g and micropore volume with 1 cm3/g.And the optimal activated mesophase semi-coke(the coarse)synthesized with the wide area streamline mesophase semi-coke,because the lamellar structure of the mesophase semi-coke is conducive to the activation of KOH layer-by-layer,in the same time,the activation energy of KOH and the internal C atom reaction is lower.The specific capacitance reached the highest value,up to 225.90 F/g.