Study On Hydrogenation Of Nitroaromatics Catalyzed By Monometallic Pt,bimetallic Cu-Ni Nanocatalysts

The crystal structure,composition,morphology and so on of nanometallic catalysts have important influence on their catalytic performance,the preparation method plays a key role in realizing the controllable preparation of nanometallic catalysts with different microstructure.This study used strong electrostatic adsorption and electroless deposition to achieve the preparation of highly dispersed,particle size controllable supported monometallic Pt nanocatalysts;bimetallic Cu_xNi_y nanometallic catalysts were prepared by wet chemical reduction.The relationship between catalyst structure and preparation conditions was studied,and the hydrogenation activity of monometallic Pt catalysts and bimetallic Cu_xNi_y nanocatalysts was studied.The specific research results are summarized as follows.（1）Preparation and catalytic performance of supported Pt/Ti O₂ nanocatalysts.Pt/Ti O₂ catalysts with Pt loading of 0.5-7.4wt%were prepared by the combination of strong electrostatic adsorption and electroless deposition.The model reaction of 4-aminophenol was prepared by catalytic hydrogenation of 4-nitrophenol.The effects of reaction temperature,feedstock concentration,hydrogen pressure and catalyst loading on their catalytic activity were studied.The results show that the prepared Pt/Ti O₂（average particle size 2.0-3.6 nm）nanocatalysts have high dispersion,as the prepared Pt/Ti O₂ was used as catalyst for the hydrogenation of p-nitrophenol,exhibit excellent catalytic activity at low temperatures.And when 0.5wt%Pt/Ti O₂ was used as catalyst,at a reaction temperature 20 ℃,4-nitrophenol concentration 0.048 mol L^-1,catalyst 3wt%,when H₂ pressure is 0.8 MPa,the conversion of 4-nitrophenol and the selectivity of target product 4-aminophenol were 100%respectively.（2）Preparation and catalytic performance of supported Pt/C nanocatalysts.Combined with strong electrostatic adsorption and electroless deposition,Pt/C nanocatalysts with Pt loading of 5.1wt%,10.9wt%and 16.5wt%were prepared.Preparation of 4-aminophenol by catalytic hydrogenation of 4-nitrophenol,the effects of reaction temperature,raw material concentration,hydrogen pressure and catalyst loading on the reaction were studied.The results show that,Pt/C catalysts have shown excellent dispersion,the average particle size of Pt nanoparticles is 2.4-3.0 nm.Based on the prepared Pt/C,the selectivity of target product 4-aminophenol was 100%.And with 16.5wt%Pt/C as the catalyst,when the raw material concentration is 0.0048 mol L^-1,H₂ the pressure is 0.5 MPa,the catalyst dosage is 2wt%,after 10 h of reaction at 80℃,the conversion of 4-nitrophenol reached 99.8%.（3）Bimetallic Cu_xNi_y nanoparticles were prepared by wet chemical reduction with nickel acetate and copper nitrate as raw materials and hydrazine hydrate as reducing agent.The co-existence of metal Cu⁰ and metal Ni⁰ components facilitates the formation of small size metal nanoparticles in bimetallic Cu_xNi_y nanoparticles.The bimetallic Cu_xNi_y nanoparticles exhibited higher catalytic activity in the catalytic 1-nitroanthraquinone hydrogenation compared with monometallic Cu⁰ and Ni⁰nanoparticles.The dispersion of metal Ni⁰ nanoparticles and the interaction between metal Ni⁰ and Cu⁰ may play an important role in the catalytic hydrogenation of 1-nitroanthraquinone.The catalytic hydrogenation of 1-nitroanthraquinone 4 h,1-nitroanthraquinone conversion was 99.7%and the selectivity of 1-aminanthraquinone was 98.7%at 120℃.