Synthesis Of Cu_x-Ni/Ni（OH）₂/RGO Nanocomposites And The Catalysis In Hydrogenation

As metal catalysts,transition metals have been developed for taking place of the role of preciousmetals in synthetic chemistry.Among them,copper and nickel,which could be used as excellent catalysts for dehydrogenation and hydrogenation,have always been catching researchers’attentions.However,the nanoparticles of transition metals are easily oxidized when exposed in air.What’s more,catalysts with high activity usually require the specific surface area as large as possible.Besides the great specific surface,graphene oxide（GO）can enhance the dispersity of metals because of the rich functional groups on GO surfaces,strengthen the synergistic effect to promote the catalytic activity,and hence has been widely used as the supporter.Catalytic hydrogenation is a basic reaction and plays an important role in chemical engineering,and can be divided into two types:one is direct hydrogenation of unsaturated bonds,such as olefins and alkynes;the other is hydrogenation accompanying by the breakage of other chemical bonds,such as hydrodeoxygenation and hydrodesulfurization.In this work,Cu_x-Ni/Ni（OH）₂/RGO nanocomposites were synthesized at room temperature,and employed as catalysts for the hydrogenation of styrene,phenylacetylene and furfural.The catalytic activity and selectivity of these catalysts were discussed from these reactions.The main research contents include:1.Cu_x-Ni/Ni（OH）₂/RGO nanocomposites were prepared by co-reduction at room temperature.The size of Cu nanoparticles on the surface of Ni/Ni（OH）₂/RGO by changing the molar ratio of copper and nickel.The results from the nanocomposite characterizations show that hydrazine hydrate could reduce Ni（OH）₂ on the surfaces of the nanocomposites to Ni⁰,and the GO to reduced graphene oxide（RGO）at the conditions.Furthermore,it is confirmed that there are a number of Cu nanoparticles with the different sizes and the exposed crystal face of Cu（111）through TEM,HRTEM,XRD,XPS and SAED measurements.2.Cu_x-Ni/Ni（OH）₂/RGO nanocomposites were used as catalysts for the hydrogenation of styreneand phenylacetylene as the hydrogen source is hydrazine hydrate.It is shown that reaction temperature can strongly affect the hydrogenation.The yield increases with the increasing temperature,but does not change with the reaction temperature when the temperature reaches the boiling point of solvents.The catalytic activity of Cu_x-Ni/Ni（OH）₂/RGO depends on the size of the Cu nanoparticles loaded on nanocomposites.With the increase of the Cu nanoparticles in size,the yield increases firstly and then decreases,which is attributed to the synergistic catalytic effects of Cu nanoparticles and Ni⁰.3.Cu_x-Ni/Ni（OH）₂/RGO nanocomposites were used as catalysts for the furfural hydrogenationwhich can produce a lot of chemicals.Using Cu_x-Ni/Ni（OH）₂/RGO as catalysts,the hydrogenation product of furfural is 2-methylfuran（2-MF）through optimizing reaction conditions from temperature,solvent and the composition of catalysts.The yield of 2-MF can reach 92.15%at 180°C in 1,4-dioxane.The size of Cu nanoparticles,the crystal face of Cu（111）and the content of nickel can influence on the catalytic activity and selectivity.In addition,the study of the reaction in different mixed solvents shows that the polarity of solvent can significantly effect on the 2-MF yield.The solvent effect could adjust the adsorption and desorption of product and weaken the coke on the catalyst surface,and hence improve the activity and recycling stability of Cu_x-Ni/Ni（OH）₂/RGO.