Selective Hydrogenation Of 3-nitrostyrene Catalyzed By Oxide-supported Pt

Selective hydrogenation reaction is widely used in fine chemicals,such as the production of spices,perfumes,pharmaceuticals,pigments,dyes,and agrochemicals.Aromatic amines containing reducible groups as key components of fine chemicals(e.g.,pesticides,dyes,pigments and pharmaceuticals)and bulk chemicals(e.g.,polymers)are prepared by selective hydrogenation of corresponding nitro aromatic.Although platinum(Pt)as a heterogeneous catalyst has been widely used in the hydrogenation industry.Due to its specific electronic structure and geometric structure,traditional Pt catalysts are usually highly active,but have great difficulty in discriminating competitive functional groups in many cases.Therefore,it is still an important issue in the field of catalytic chemistry and chemical engineering to explore the fine structure and electronic modulation of Pt based catalysts and their mechanism of action affecting the hydrogenation performance of 3-nitrostyrene.To solve this issue,in thesis thesis,we synthesized two series of Pt-supported catalysts by concisely varing the Pt-oxide support interactions,The tructural and electronic properties of the catalysts were characterized by XRD,XPS,TEM,and CO-DRIFTs techniques.Moreover,the catalysts were comparatively evaluated for the selective hydrogenation of 3-nitrostyrene as model reaction,and the structural changes of the representative catalysts during the reaction were studied by the identical location-transmission electron microscopy(IL-TEM)technique.With the characterization and reaction results,the effect of the electronic and geometric properties of the catalysts on the catalytic performance was rigorously revealed,and the possible reaction mechanism was proposed.The main results consist of following parts:(1)ZnO nanorods support Pt nanoparticles(NPs)for the selective hydrogenation reaction of 3-nitrostyrene.By directly loading metallic Pt NPs with narrowly distributed particle size over well structured ZnO nanorods followed by the succeeding thermal treating in a reductive atmosphere,the electronic and geometric effects of the Pt component on the surface of ZnO supports were finely adjusted,which was an effective strategy to optimize the selectivity of the Pt-based catalyst in the hydrogenation of 3nitrostyrene.The results show that the PtZn intermetallic nanoparticles formed by the reduction treatment at 300? can selectively adsorb nitro groups and have a good selectivity for the target product(3-vinylaniline).In addition,IL-TEM method was used in the reaction system to study the behavior of the active sites on the surface of the Pt/ZnO catalysts obtained by different temperature reduction treatment in the reaction process,and the stability of the catalyst under the reaction conditions was revealed.(2)Tailoring surface structure of iron oxide nanorods to support Pt NPs for the selective hydrogenation reaction of 3-nitrostyrene.Iron oxides with different structures were prepared by the calcination of ?-FeOOH precursor as supports and further supported Pt by EG reduction method.The results show that the surface structure of FeOOH can enhance the dispersion and stability of the platinum component compared with Fe3O4 and?-Fe2O3,making it more active in the selective hydrogenation reaction of 3-nitrostyrene.And the electronic structure of Pt could be affected by surface structure of iron oxide supports,making it have excellent selectivity in the reduction reaction of 3-nitrostyrene.