Dielectric Properties Of Activated Carbon Preparated By Conventional And Microwave Heating

Activated carbon,as a functional carbon material with developed pore structure,large specific surface area and strong adsorption,was widely used in various fields,such as military industry,chemical industry,light industry,semiconductor,battery and electric energy storage.With the development of microwave technology,more and more fields have received extensive attention,such as production of activated carbon by microwave heating,microwave regeneration of activated carbon,microwave modified activated carbon,microwave irradiation activated carbon desulfurization and denitrification technology.However,the temperature change of activated carbon in the microwave field is mainly determined by its dielectric properties and expressed as a complex permittivity:?=??-j??.Therefore,it is necessary to explore the variation of the dielectric properties of activated carbon in order to provide the necessary experimental data and reasonable theoretical support for the application of activated carbon in the microwave field.The thesis used Hainan coconut shell,Jincheng anthracite coal and waste plastic bottle?PET?as research objects.Through the traditional heating and microwave heating methods,KOH,ZnCl₂ and H₃PO₄ were used as activators to prepare activated carbon.X-ray diffraction analysis,FT-IR and the N₂adsorption method were used to characterize the microcrystalline structure and pore structure of activated carbon respectively.The dielectric properties of activated carbon were measured by vector network analyzer.The conclusions were obtained from experimental research and analysis processing.?1?Activated carbons were prepared by coconut shell,anthracite,and waste plastic bottles?PET?with KOH under traditional heating.coconut shell activated carbon has a maximum BET specific surface area and the highest order of carbon atoms.The BET specific surface area of PET activated carbon is larger than that of anthracite activated carbon,but its carbon atom has the lowest order.The dielectric loss tan?of coconut shell activated carbon is the largest,and the dielectric loss tan?of PET activated carbon is slightly smaller than that of anthracite activated carbon.?2?Comparison of activated carbons prepared by microwave heating and traditional heating with coconut shell as raw material and H₃PO₄ as activator.It was found that the micropores in the activated carbon prepared by microwave heating were further developed into mesopores.Intermittent discharge phenomenon was occured during the preparation of activated carbon by microwave heating,which improved the order of carbon atoms in activated carbons.The dielectric loss tan?of the activated carbon prepared by microwave heating is larger than that of the conventionally prepared activated carbon.?3?Comparison of activated carbons prepared by traditional heating with KOH,H₃PO₄ and ZnCl₂ as activators and coconut shell as raw material.It was found that the carbon atom prepared by KOH had the smallest order of carbon atoms,but its BET specific surface area was up to 2643.14m²/g.During the activation process,KOH reacted with the carbon atoms in the materials,which caused lattice defects of the microcrystalline carbon in the activated carbon and formed an additional polarization center,ultimately the dielectric loss tan?of activated carbon prepared by KOH was the largest.The BET specific surface area of activated carbon prepared by ZnCl₂ was larger than that of H₃PO₄,and its carbon atom order was the highest.Therefore,the dielectric loss tan?of activated carbon prepared by ZnCl₂ was greater than that of activated carbon prepared by H₃PO₄.?4?Comparison of activated carbons prepared by microwave heating with KOH,H₃PO₄ and ZnCl₂ as activators and coconut shell as raw material.The BET specific surface areas of the three activated carbons were small,and the dielectric loss was mainly related to the order of carbon atoms.The activated carbon prepared by ZnCl₂ had the highest degree of carbon atom order and the dielectric loss tan?was the largest.Although the carbon atom prepared by KOH had the least order of carbon atoms,it formed polarization centers during the activation process.The dielectric loss tan?of the activated carbon prepared by KOH was larger than that of the activated carbon prepared by H₃PO₄.