Synthesis Of Microporous And Mesoporous Carbon Materials For Catalysis And Adsorption

Porous carbon materials are now attracting great research interests due to their high thermalstability, extremely large surface area large and chemical inertness. And has been widely used inareas of catalysis, adsorption, hydrogen storage and electrochemistry etc. In this thesis, a seriesof porous carbons and carbon-based nanocomposites with ordered mesoporous structure ormicroporous strucuture were fabricated. These carbons were also functonalized and applied ascatalysts for propane dehydrogenation, adsorbents for CO₂capture and dye decorlorizaiton.1. Supermalecular aggregate and assembly is an effective method for synthesis of mesoporouscarbon materials. Ordered mesoporous carbon materials （OMCs） were synthesized with the useof citric acid as an environmentally friendly catalyst to catalyze the polymerization ofresorcinol/formaldehyde resin. The obtained carbon materials with high thermal stability have a2-D hexagonal mesopore system with uniform pore size of⁵.2nm and a high surface area of612⁸51m²/g, which were available under a wide composition range of reaction system, withreaction temperature of50–80oC and the molar ratio of formaldehyde to citric acid≥3. Thepresence of citric acid in the synthesis system can enhance the hydrogen bonding betweentriblock copolymer and resol and further introduce more micropores to the final carbon material,which is favorable for CO₂adsorption. The nitridation of the OMCs in ammonia flow at thetemperature of650^-1000oC is demonstrated to be effective in introducing basic functionalitiesthat enhances the specific interaction of CO₂and adsorbent. The N-doped OMCs exhibitenhanced CO₂uptake with CO₂capture capacity of3.46mmol/g for1000oC-nitrided sample.Both textual and surface chemistry influenced the CO₂capture performance of the resultantmesoporous carbon adsorbents.2. Monolithic carbons with ordered mesopores were used as catalyst for dehydrogenation ofpropane to propylene, exhibiting high catalytic activity and stability. After50hours in steam, thepropane conversion of12.1%was observed with propylene selectivity of95.1%in the directdehydrogenation process, while the propane conversion of20.1%with propylene selectivity of25.8%in oxidative dehydrogenation process. It has been found that the surface basic groups controlthe catalytic turnover. Activated with HNO3could dramatically improve the catalytic activity of themesoporous carbon, exhibiting high selectivity and stability. The final propane conversion is22.4%with stable propylene selectivity of86.6%after50hours. HNO3activation introduces more basicoxygen groups than the pristine carbon, which is believed to be active site in the dehydrogenationprocess. 3. Spherical nitrogen-containing polymer and microporous carbon materials have beensynthesized by using hexamethylenetetramine as nitrogen source and one of the carbonprecursors under solvothermal conditions, without using any surfactant and toxic reagent suchas formaldehyde. The synthesis strategy is cost-effective and can be easily scaled up forproduction. The microporous carbon spheres exhibit high surface areas of528936m²g^-1withmicropore size of0.61.3nm. The synthesized microporous carbons show a good capacity tostore CO₂, which is mainly due to the presence of nitrogen-containing groups and a largeamount of narrow micropores （<1.0nm）. At1atm, the equilibrium CO₂capture capacities ofobtained microporous carbons are in the range of3.95.6mmol g^-1at0oC and2.74.0mmolg^-1at25oC. Core-shell structured nitrogen-rich microporous carbon materials were alsoprepared by introducing the melamine-formaldehyde （MF） resin as co-carbon precursor. Thistype of carbon material contains a large amount of nitrogen-containing groups with the700oC-carbonized sample as high as7.92wt%and consequently basic sites, resulting in a fasteradsorption rate and a higher adsorption capacity (4.3mmol g^-1) for CO₂than pure carbonmaterials (3.4mmol g^-1) under the same conditions. The potential for large scale productionand facile regeneration makes this material useful for industrial applications.4. Mesoporous carbons with specific surface areas in the range of310–892m²g^-1, mesoporevolumes in the range of0.40–1.22cm3g^-1are prepared by using crude attapulgite, calcinedattapulgite and HCl-treated attapulgite as inorganic templates and resorcinol-formaldehyde resin asthe carbon source through impregnation method. The influences of the calcination temperature andHCl concentration on the pore structure of the resultant carbons are investigated. The results indicatethat the the calcination temperature and the HCl concentration are600oC and4M, respectively, andthe corresponding carbons have the maximum surface areas and mesopore volumes. Adsorption oflosyzyme on the mesoporous carbons in aqueous solution reveals that the equilibrium adsorptioncapacities （qe） are in the range of13.4–33.1μmolg^-1. It was also found that the monolayeradsorption capacity increased with increasing the accessible specific surface area and the porevolume. The large mesopores and their hierarchical porous structure could facilitate the easydiffusion of protein molecules, and also be responsible for the excellent adsorption capability forproteins. Moreover, the obtained carbons exhibit high CO₂capture capacity of1.102.78mmol g^-1.5. Hierarchical mesoporous carbon-titania nanocomposites with nanocrystal-glass frameworkshave been synthesized via the organic-inorganic-amphiphilic coassembly by using resol polymer as acarbon precursor prehydrolyzed TiCl4as an inorganic precursor, and triblock copolymer F127as atemplate. The carbon-titania nanocomposites with controllable texture properties and compositioncan be obtained in a wide range from0to85wt%TiO₂by adjusting the initial mass ratios. TheC-TiO₂nanocomposites exhibit high thermal stability up to700°C, high surface area of200–355 m²g^-1and hierarchical pore size （5.2nm,6–18nm）. Additionally, the nanocomposites show goodperformance in decolorizaiton of Rhodamine B due to the photocatalytic activity of the titaniananocrystals and the strong adsorptive capacity of the porous carbon.