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Synthesis And Application Of Mesoporous Carbon Supported Nano Metal Catalysts

Posted on:2019-03-06Degree:MasterType:Thesis
Country:ChinaCandidate:J W FuFull Text:PDF
GTID:2351330548455539Subject:Physical chemistry
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Metallic nanomaterials are widely used in chemistry,physics,biology,medicine and other fields due to their surface effect and small size effect and their unique chemistry,electrochemistry and optical properties.Mesoporous carbon materials is a kind of commonly used metal catalyst carrier,it has a uniform distribution of pore diameter and highly ordered channel distribution,large specific surface area and pore volume,in areas such as hydrogen storage,catalyst,electrode materials show great potential applications.In this paper,the surfactant self-assembly method is used to obtain two kinds of nano-metal catalysts.The particle size distribution is uniform and the stability is strong.The catalytic properties of two kinds of catalysts were investigated by hydrogenation of aromatic nitro compounds and Fischer-Tropsch synthesis reaction.In the first part,gold nanoparticles were supported on different oxide supports and used for the selective hydrogenation of aromatic nitro compounds.Using thiol coordination and the physical limitation of the mesoporous wall not only avoid the use of a protective agent but also confine the gold nanoparticles in the carbon-silicon framework,limiting the growth of the nanoparticles.Different size gold nanoparticles oxide supported were obtained through in-situ reduction of gold nanoparticles by small molecules such as methane and carbon monoxide decomposed by high-temperature calcination.The 9 nm gold nanoparticles were selectively pretreated by sulfuric acid to get 3 nm gold nanoparticles.Even though the calcining temperature rose to 700°C,gold nanoparticle agglomeration was not observed,indicating that the prepared catalysts have high thermal-stability.In the hydrogenation of 3-nitrostyrene,the silica-supported gold catalyst is not catalytically active because of the large particle size of the gold nanoparticles and silica as an inert support.The conversion frequency?TOF?of the manganese dioxide-supported gold catalyst?5 nm?is higher than that of the ruthenium dioxide-supported gold catalyst?8 nm?,suggesting that the particle size is a major factor affecting the catalytic activity.In the 4-nitrostyrene hydrogenation reaction,the manganese dioxide-supported gold catalyst has no catalytic activity,indicating that the active carrier is the main reason for catalytic activity.The 3 nm gold catalyst was used for the reduction reaction of aromatic nitro compounds of different sizes,exhibiting higher catalytic activity and stability,and the conversion and selectivity of the aromatic nitro compounds were all up to 100%.No obvious loss of Au and decrease of activity were observed after reuse of the catalyst for 6 times,indicating that the catalyst has high stability and the active center is gold nanoparticles immobilized on the carrier.In the second part,an iron-based catalyst supported on mesoporous carbon was prepared and used for Fischer-Tropsch synthesis?FTS?reaction to investigate the catalytic performance.The calcination temperature affects the formation of the iron phase.The Fe3O4 phase is obtained at a temperature of 500°C,and the carbon monoxide and methane decomposed from the phenolic resin at a temperature of600°C to 800°C are carbonized to obtain a?-Fe3C phase.As the calcination temperature increases,the particle size increases from 8 nm to 25 nm.The catalyst calcined at 600°C was used for the FTS reaction,and the catalyst had a high selectivity to light olefins.
Keywords/Search Tags:gold nanoparticles, iron carbide, mesoporous carbon, nitro-slective hydrogenation, Fischer-Tropsch synthesis
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