Synthesis And Characterization Of A Novel Passivated Ni/SiO₂ Catalyst And Its Application In Various Reduction Reactions Of Nitro

Noble metal catalyst has high reaction activity,but it is deactivated easily and expensive.Nickel catalyst,is very cheap and relatively stable,not easy poisoned, although with a lower initial activity.Nickel catalysts have already had the trend to replace the precious metal catalyst in a number of non-refined industries of the world.In recent years,our laboratory have developed a novel passive supported nickel catalyst,my primary work is making a series of characterizations of the nickel catalyst and exploring its applications in a variety of nitro-reduction reactions.1.A green reduction of aromatic nitro compounds to aromatic amines over a novel Ni/SiO₂ catalystAromatic amines and their derivatives are important intermediates.We have prepared a novel Ni/SiO₂ catalyst by the technologies of deposition-precipitation and surface passivated,and firstly put it into the process of synthesis amine from aromatic nitro compounds.In our experiments,Ni/SiO₂ is found a highly efficient,stable and reusable catalyst for the reduction of aromatic nitro compound.Vary aromatic amines is achieved while using the catalyst,and the probable reason is that the passivated Ni/SiO₂ catalyst has lower activity and doesn't destroy sensitive groups in comparison with other reported catalysts.The major advantage of this catalyst is as follow:it can be stored safely in air below 423K and need no activation before use;can be easily prepared and scaled up easily;mild reaction conditions;catalytic system is environmentally friendly,ethanol as sole solvent;the product can be conveniently separated using filtration or magnetic separation;high conversion and selectivity,almost without by-products;sensitive functional groups,such as-OH,-Cl,-CH₃,-CHO,-CH₂OH,-COCH₃,-OCH₃ and -NHCOCH₃,remain unaffected in the reaction condition.2.One pot synthesis of imines from aromatic nitro compounds with a novel Ni/SiO₂ magnetic catalystImines and their derivatives are versatile intermediates in organic synthesis,in particular for the preparation of heterocycles,non-natural aminoacids,anti-cancer agents and liquid crystalline materials.There are three main synthesis routes:direct synthesis of imines[acid catalyst and dehydration];one-pot synthesis of imine with oxidation[oxidation,acid catalyst and dehydration];one-pot synthesis of imine with reduction[reduction,acid catalyst and dehydration].Ni compounds are excellent catalysts for the reduction of nitroaromatics and SiO₂ is a commonly-utilized catalyst for imine formation.It seemed promising that Ni/SiO₂ can be an effective bifunctional catalyst for one pot synthesis imines from nitroaromatics.We put it to one pot synthesis imines from nitroaromatics for the first time.We found the optimal reaction conditions,explored different catalyst system;in the best conditions,we have synthesis a large number of imines with vary complex substituents in the optimal conditions.It maybe has good use in the synthesis of heterocycles,amino acids,anti-cancer reagents and liquid crystal material.Catalyst can be conveniently recycled and reused.One-pot synthesis is a method that without separation intermediates,saving costs and environmental friendly.