Hydrogenation Of Nitroaromatics With H₂ To Arylamines Catalyzed By Copper-based Nanocatalysts

At present,the research of functional nanomaterials is very important on the basis of metal Cu nano-catalyst.A series of bimetallic Cu-based nano-metal catalysts with specific structure and morphology were designed and constructed,which can change the electronic properties and geometric structure of the active components of the catalysts to improve the catalytic performance of Cu-based nano-catalyst.In this paper,the structure-activity relationship between the morphology of copper-based nanocatalysts and the catalytic performance of catalytic hydrogenation of nitroaromatics to arylamines was studied.The research results are summarized as follows.Bimetallic CuPt_x nanoparticles were prepared in ethanol solution by the wet chemical reduction method using Cu?NO₃?₂ and H₂PtCl₆ as starting materials,hydrazine hydrate as a reductant,and polyvinyl pyrrolidone as an organic modifier.The average particle sizes of Cu and Pt nanoparticles were 60 nm and 3 nm,respectively.The small-sized Pt nanoparticles were evenly anchored at the surfaces of large-sized Cu nanoparticles.In the bimetallic CuPt_x nanoparticles,electron was transferred from platinum to copper species,which increased the selectivity of1-aminoanthraquinone by suppressing the high hydrogenation activity of metallic platinum.The hydrogenation of 1-nitroanthraquinone was catalyzed by the bimetallic CuPt_0.1.1 nano-catalyst to produce 1-aminoanthraquinone.The reaction was carried out at 140 ^oC for 4 h.The conversion rate of 1-nitroanthraquinone was 98.9%,and the selectivity of 1-amino-anthraquinone was 99.3%Cu_xNi_y alloy nano-metal particles with small particle size?17²5 nm?and narrow size distribution?7⁴0 nm?were successfully prepared by wet chemical reduction method using sodium dodecyl sulfate as modifier,hydrazine hydrate as reducing agent.And the as-prepared Cu_xNi_y nanoparticles are used for for the hydrogenation of p-nitrophenol to p-aminophenol with H₂.At the reaction temperature of 120 ^oC and the pressure of 0.8 Mpa H₂,the hydrogenation of p-nitrophenol catalyzed by Cu_0.2Ni_0.8.8 alloy nanocatalyst for 4 h,and the conversion of p-nitrophenol and the selectivity of p-aminophenol reached 100%.Monometallic Cu,monometallic Ni,and bimetallic Cu_xNi_y nanoparticles were prepared by a wet chemical reduction method.Cu–Ni alloy phase was formed in the bimetallic Cu_xNi_y nanoparticles.The bimetallic Cu_x Ni_y nanoparticles exhibited higher catalytic activity for the hydrogenation of 3-nitro-4-methoxy-acetylaniline to3-amino-4-methoxy-acetylaniline with H₂ than the sole Ni nanoparticles,which was ascribed to the effect of the Cu–Ni alloy phase.When the reaction was catalyzed over thebimetallicCu_0.7Ni_0.3catalystat140^oCfor2h,the3-amino-4-methoxy-acetylanilineselectivitywas99.4%Whilethe3-nitro-4-methoxy-acetylaniline conversion was 95.7%.The kinetic equation of the catalytic reaction is r₀=-dn₀/(dt·W_cat)=13.59 exp?-19.74/RT?C₀⁰.45.45 P₀¹.15.15 mol h^-11 g^-1,the reaction activation energy for 3-nitro-4-methoxy-acetylaniline hydrogenation was19.74 kJ/mol.