Synthesis Of Iron-based Catalysts And Their Application In Hydrogenation Of Nitrobenzene

Iron-based catalysts exhibited excellent performance for ammonia synthesis,the production of olefins?via Fischer-Tropsch synthesis?,selective catalytic reduction of NOx,and so on.It is of great significance to explore new applications and mechanisms of iron catalysis,which has attracted many attentions for its abundance,low price,and nontoxicity.Selective hydrogenation of nitroarenes is of great importance as anilines are important commodity chemicals in the production of methylene diphenyl diisocyanate?MDI?,polyurethanes,dyes,and explosives.We hope to find a kind of efficient,stable,easily separated and reusable use iron-based catalyst through the research on iron-based catalysts for selective hydrogenation of nitrobenzene and the reaction mechanism.First,a convenient and stable iron oxide?Fe₂O₃?-based catalyst,in which active Fe₂O₃ nanoparticles?NPs?were embedded into carbon films,was prepared via the pyrolysis of iron-polyaniline complexes on carbon particles.The Fe₂O₃@G-C-900 composite was highly active and stable for the direct selective hydrogenation of nitroarenes to anilines under mild conditions.The conversion of NB over Fe₂O₃@G-C-900 reached 95.4%with a 99.1%selectivity to AN?70 ?,p?H2?= 2.0 MPa,2.0 h?.When acid-pretreated XC-72R particles and other commonly used supports,such as SiO2,Al2O3 and MgO,were used as the support,the conversion of NB and selectivity to AN decreased sharply.At the same time,it was found that the hydrogenation of NB performed mainly in a direct routine which can depress the formation of those byproducts with high boiling points.The excellent performance of Fe₂O₃@G-C-900 was thought to be attributed to its high specific surface area,large pore volume,highly dispersed Fe₂O₃ NPs and the synergetic interaction between the Fe₂O₃ NPs and the protective carbon films.Furthermore,N in the carbon films herein not only brought imperfect and porous encapsulation,but also enhanced the catalytic activity of the carbon surface around the Fe₂O₃ core.It was found that Fe₂O₃@G-C-900 showed a superior activity in the hydrogenation of a series of nitroarenes,and nitroarenes with para-substitutions proceeded easily compared with meta-and ortho-substituted substrates.Carbon supports play an important role in governing catalyst performance.In order to verify the effect of carbon supports,a convenient and stable iron oxide?Fe₂O₃?-based catalyst was prepared via the pyrolysis of graphene oxide,aniline and ferrous acetate at varied temperature?denoted as Fe₂O₃/rGO/N-rGO?,in which active Fe₂O₃ nanoparticles?NPs?were supported on composite carbon films composed of reduced graphene oxide and nitrogen-reduced graphene oxide.The pyrolysis temperature had a great influence on the size of metal nanoparticles and the morphology of catalysts,which made the catalytic activity different.It was found that Fe₂O₃/rGO/N-rGO-700 composite was highly active and stable for the direct selective hydrogenation of nitrobenzene to aniline.At the same time,it was found that the hydrogenation of NB performed mainly in a direct routine which can avoid a series of problems such as the separation issues,impurities in the final product and catalyst deactivation.