Investigation On Preparation And Application Of Structured Catalyst Modified By Carbon Nanoifbers

M-Phenylenediamine is an important organic intermediate for thesynthesis of some polymers, dyestuff and other materials. The catalytichydrogenation technology of m-phenylenediamine is favored by the enterprisehome and abroad instead of the iron-acid reduction method, owing to itsadvantages such as less pollution to environment. The common reactor forhydrogenation is the slurry reactor because of its high conversion ofm-dinitrobenzene and the selectivity of m-phenylenediamine. Howerer, itneeds additional costs for separation of the catalyst from the products.Although this can be solved in the trickle bed reactor, but the selectivity is low.Structured reactor can combine the advantages of above reactors. As a result,it is practically significant to develop the catalytic hydrogenationm-dinitrobenzene to m-phenylenediamine in structured reactor. In this thesis,the honeycomb support is coated with γ-Al₂O₃and then modified by carbonnanofibers via methane catalytic decomposition. Finally, the catalyticactivities of the new support have been evaluated after being loaded Pd.The honeycomb cordierite ceramic is kind of structured support which isused most widely. However, it presents very low specific surface areas.Therefore, the honeycomb cordierite was washcoated with a layer of porousmaterial, such as γ-Al₂O₃. The orthogonal experimental method was adoptedto inspect the influence of suspension liquid solid content, coating time andcoating circles on the property of γ-Al₂O₃coating. Researches indicated thatcoating circle is the greatly impact factor to the BET surface of structuredcatalyst, followed by suspending liquid solid content and the last is coatingtime. The optimization process conditions for coating γ-Al₂O₃are25%suspension liquid solid content, coating2min and3circles.Then, in-situ coating CNFs and CNTs on cordierite monolith fromcatalytic decomposition of methane was investigated using nitrogen physisorption, SEM and TEM. It was found that the surface area of monolithcould be effectively increased after coating CNFs/CNTs on the monolith wall.Firstly, the effect of preparation conditions of catalyst on catalyticdecomposition of methane is studied. When being prepared with15wt.%ofγ-Al₂O₃coating,15wt.%Ni loading and dipping in1h, the catalyst possesseshighest activity. Secondly, the textural structure of the coated monolith isdependent on the morphology of the coated CNFs/CNTs and the entanglementbetween them. The high growth temperature and the addition of hydrogen inthe reaction gas are advantageous to the formation of CNT coating layers.Thirdly, the coating layers of CNFs have a better stability than that of CNTsin ultrasonic treatment by comparison.Finally, the performance of the CNF modified monolith was alsoinvestigated in catalytic hydrogenation of m-phenylenediamine reaction. Theresults showed that the conversion of m-dinitrobenzene and the selectivity ofm-phenylenediamine are83%and72%, respectively. In addition, the CNFmodified monolith shows good stability. The optimized reaction conditionsneed further research.