The Synthesis Of Porous Nickel(Cobalt) Nitrides And Their Application For The Catalytic Reduction Of Aromatic Nitro-Compounds

With the development of modern industry.a large number of aromatic nitro compounds are discharged into water.These compounds need long period for the degradation.high toxicity.bioenrichment etc.Therefore.it is urgent o develop efficient methods for the removal/conversion of these compounds from water.The catalytic reduction by using NaBH4 as a reducing agent can convert highly toxic aromatic nitro compounds into amino compounds with low toxicity,easy degradation and high added value,thus being an effective way to reduce the pollution of aromatic nitro compounds.Noble metal nanomaterials are important hydrogenation catalysts,but its usage is restricted by the low reserve and high cost.Therefore.the researchers have paid to the intensive interest in the development of cheap non-noble metal catalysts.The Co and Ni-based nitrides have noble metal-like electronic structure and good magnetic properties,being favorable for the catalytic application.Their properties are governed by the size,pore structure and morphology.Based on this,this thesis is devoted to the development of a new method for the synthesis of porous cobalt(nickel)-based nitride,which can be use as highly efficient and magnetically separated catalysts by adjusting the morphology and pore structure.Two dimensional porous sheet materials of cobalt-nickel-based nitrides and one dimensional tubular nickel-based nitrides were prepared by solvent-assisted and organic ligand-induced reaction.The main contents of this paper are as follows:(1)The sheet precursor of cobalt nickel-metal hydride was synthesized by the reaction of nickel nitrate,cobalt nitrate and anhydrous sodium acetate with polyethylene glycol with abundant hydroxyl groups.The surface of hydroxide was modified by 3-aminopropyl triethoxy silane(KH550).and the excessive aggregation and growth of particles were inhibited by silica derived from KH550 during pyrolysis.By optimizing the synthesis conditions,the cobalt-nickel molar ratio,the temperature of heating treatment and the nitriding time,the wo-dimensional porous sheet structure composed of small particles of CoNiN is finally obtained.The catalytic performance was evaluated by using p-nitrophenol(4-NP,0.3 mM)as the pollutant,and the nearly complete conversion was achieved in 2.5 min.At the same time,the optimized catalyst has good catalytic activity for many kinds of nitroaromatic compounds.It is worth noting that cobalt nickel nitride has good magnetism,which can be separated from the reaction solution by an external magnet and has good recycling performance.(2)By using polyvinylpyrrolidone(PVP)as a structure-directing agent,a one-dimensional tubular material of nickel-butanedione oxime chelate is synthesized at room temperature through the coordination and complexation reaction of diacetyl oxime and nickel salt.It was found that the addition of PVP was the key factor to form the tubular structure,and the products formed without PVP were mainly composed of nanorods.The complexes were transformed into nitrides by a two step heat treatment.First,the oxide tubes were prepared by calcination in air,and then the one-dimensional nickel nitride nanotubes were prepared by heating treatment of oxide tubes under NH3 atmosphere.For the hydrogenation reduction reaction of 4-NP(0.3 mM),the catalyst showed good activity.The effective conversion could be realized in 2 minutes.Moreover,the catalysts shows good catalytic activity for a variety of nitro compounds.The Ni3N-350 catalyst can be separated and reused with a assistance of strong magnetic magnet.The tests show that the catalyst has excellent recycling performance,and can remain the high catalytic efficiency even after 15 times of recycling uses.