Fabrication Of Magnetic Pt/C Catalysts For Hydregonation Of Nitrobenzene

Nitrobenzene hydrogenation is an important reaction in organic chemistry, as aniline is used as basic raw materials for production of methylene diphenyl diisocyanate (MDI), rubber chemicals, dyes and pharmaceuticals. Most of global aniline is produced by catalytic hydrogenation of nitrobenzene. It is noted that Pt-based nanocatalysts show high activity and selectivity in this reaction. To keep high dispersion of active components under reaction conditions, porours carbons are extremely promising candidates as catalyst supports due to their unique physical and chemical properties, such as high surface areas, excellent chemical stability, and good oxidation resistance at low temperature. However, the carbon supported Pt nanocatalysts have issues with separation and recovery. In this thesis, we have developed carbon supported magnetic Pt nanocatalysts show a high catalytic activity in nitrobenzene hydrogenation, and are reusable and have magnetic separation function in liquid phase reactions.Firstly, dopamine was used as carbon precursor to coat Fe2O3nanoparticles. The polydopamine shells act as anchor sites for Pt. Finally, after thermolysis reduction process, core-shell nanocatalysts Pt/Fe3O4@C were obtained, which show a high conversion of aniline (e.g.98%) in nitrobenzene hydrogenation, and can be recyclyed by magnetic separation mean. Investigation on the recyclability of the Pt/Fe3O4@C catalysts showed excellent results in a total of four cycles, i.e., high conversion (>98%). The fifth and sixth cycles exhibited drop in conversions37%and11%, respectively. The catalyst can be regenerated by a simple calcination treatment at250℃under air. After heat treatment, this catalyst recovers its activity of high conversion (>98%).Highly engineered bifunctional yolk-shell nanocatalysts (Pt/Fe304@void@C) with tailored structural configuration, i.e. hollow carbon spheres as the matrix, entrapped Fe3O4nanoparticles in the hollow core as magnetic carrier, and the in situ formed and highly dispersed Pt nanoparticles within the carbon shells as the active catalyst sites, have been prepared. The obtained nanocatalysts was collected by a magnet for reuse, which gave again99%yield of aniline over eight consecutive runs without any dcactivation. Judging from the activity per Pt site, we carried out a catalytic reaction in which the molar ratio of nitrobenzene to Pt used was1500. After2h reaction period, the catalyst gave38%yield of aniline, with a higher turnover frequency of285h-1...