The Synthesis And Characterizations Of Ni-Pd And Ni-Co Bimetallic Catalysts And The Study Of Catalysis For Hydrogenation

Bimetallic catalysts which distinguish from their parent metals have great potential applications in chemical industry, medicine, catalysis and electronics, etc., for the synergistic effects, rich composition diversity and shape-depended effects. The size, shape and structure would be changed by controlling the reaction process and conditions when the second metal including precious and light metal is added, resulting in changing of the catalytic activity and selectivity, etc. In this paper, Ni-Pd and Ni-Co bimetals with the morphologies of nanochain and branch were successfully prepared by controlling the auxiliaries including gas (H2).Firstly, chain-like Ni-Pd nanoparticles have been prepared by polyol reduction process in which nickel (Ⅱ) acetate and palladium (Ⅱ) acetate are reduced at high temperature by1,2-propanediol in the present of polyvinyl pyrrolidone (PVP). The morphology, structure and element distribution of those nanoparticles were characterized. A possible mechanism for the formation of such Ni-Pd nanochains was proposed.Next, compositionally controlled self-assembly Ni-Pd bimetals have been demonstrated in the system of oleylamine-toluene-ethanol with TBAB, in which hierarchical Pd-Ni bimetallic chains with different assembling modes have been achieved. Based on the analyses of XRD patterns, TEM and SEM images, FT-IR spectra and M-H curves, the mechanism of the composition controlling self-assembly were illustrated, in which the self-assembly behaviours were controlled by the competition of the surfactant interaction and the magnetic dipole interaction.Then, Ni-Co bimetals with branched structure were prepared by the modified polyol method assisted with H2. The characterizations of XRD, TEM, EDX, BET and magnetism show that compared with the absent of H2, the bimetallic structure and morphology were changed with the adsorption of H2, and the surface areas were increased.Finally, the catalytic activity and selectivity of the hydrogenation of acetophenone over these Ni-Pd and Ni-Co bimetals depend on their compositions. The activities enhance with the increasing content of Pd and Co. The Pd-rich catalysts show better hydrogenation catalytic activity than Ni rich catalysts, and Ni50Pd50is the best proportional bimetals. The activity of Ni-Co with H2is higher than that of Ni-Co without H2.