Fabrication Of Shaped Hierarchical Porous Carbon Materials And The Adsorption Performance For Volatile Organic Compounds

In the shortage of resources and energy crisis,adsorption process is widely used in the treatment of VOCs due to its low energy consumption,wide range of application and recyclability of adsorbate.In the adsorption process,proper adsorbent is acknowledged as the most important parameter for the efficient removal of VOCs.However,due to the nature structure and chemical property,the existing VOCs adsorbents have many problems,such as limited mass transfer and complex forming-activation process.In order to prepare efficient adsorbent for VOCs removal,this thesis focuses on the construction of hierarchical porous structure,the regulation of surface chemical property and the formation of materials in three aspects.Hierarchical ordered mesoporous carbon(OMC)and carbon spheres(CSs)were prepared through sol-gel method using phenolic resin as carbon precursor.Then the shaped OMC and CSs/OMC foam were synthesized via adhesive forming and gel casting with FB resin and OMC gel,respectively.Porous carbon beads(PCBs and NCBs)were prepared through phase inversion route followed by carbonization with PVDF and g-O3N4 as precursors.The adsorption properties of VOCs and the influence of different forming process on formed porous carbon materials were investigated.The detailed research contents are presented as follow:(1)Shaped OMC was prepared by sol-gel method and adhesive forming method.The process route of OMC powder forming was developed through the optimization of forming parameters.The adsorption for benzene on shaped OMC was physical adsorption;compared with activated carbon,shaped OMC showed better adsorption performance,due to the hierarchical porous structure.Under moderate loading,hierarchical porous structure could facilitate the dispersion of active components and enhance the adsorption performance of H2S.Compared with microporous activated carbon,the pore structure of OMC is more conducive for dispersion of copper,which effectively inhibit the grain size growth and improve the adsorption properties.(2)CSs/OMC foams with high porosity,high pore volume,abundant micro-mesoporous structure and 3D network structure were prepared via"silica-assistant" sol-gel method and gel casting forming.The chemical property of carbon sphere was tailored by nitrogen doping.Due to the hollow structure and nitrogen doping,nitrogen doped carbon sphere(NHCS)exhibits excellent adsorption performance for benzene.The promoted desorption behaviors were own to the hollow structure.The mechanism of enhanced adsorption performance caused by nitrogen doping is clarified.With the NHCS amount of 0.10g,CSs/OMC foam presented excellent adsorption properties for benzene,attributed to better dispersion of NHCS and rich hierarchical porous structure(microporous and mesoporous and hollow structure).The pressure drop is only 24.5 Pa,far less than the traditional granular activated carbon(GAC),which can effectively reduce the energy consumption.(3)The phase inversion method in the field of membrane separation was introduced into the preparation of spherical carbons.Porous carbon beads(PCBs)with high sphericity,high strength and particle size of about 1.5 mm were successfully prepared by phase inversion route followed by carbonization.The pore structure of PCBs can be adjusted by changing the composition of the coagulation bath to control the phase inversion process.Due to the well-developed pore structure and super hydrophobicity,PCBs exhibit good adsorption performance for VOCs.PCBs-2 showed the fastest adsorption kinetics and the highest adsorption capacity for benzene,attributed to high meso-macropores content and thin skin layer.Compared with GAC and other porous carbon,PCBs-2 exhibits excellent dynamic adsorption performance under similar adsorption conditions.PCBs-2 presents good reusability used as adsorbent.(4)Nitrogen doped carbon beads(NCBs)with abundant micro/meso/macro hierarchical porous structure,high nitrogen content,polar functional groups and particle size of 1.2 mm were successfully prepared with PVDF and g-C3N4as precursors.The structure and chemical property of NCBs can be tailored via controlling the content of g-C3N4 due to its dual-function of template and nitrogen source.Owing to the abundant porous structure and chemical polarity,NCBs extend the adsorption performance for H2S under retention of adsorption for benzene.The promotion on adsorption performance for H2S from mixture could attributed to the change of electron distribution on nitrogen atom caused by the adsorbed benzene.The adsorption kinetic confirmed the enhancement on mass transfer ascribe to meso/macro hierarchical porous structure.The pressure drop is only 68.6 Pa,less than the traditional GAC,which can effectively reduce the energy consumption.