Preparation And Catalytic Performances Of Hybrid LDH/C Composite Supported Noble Metal Catalysts

Supported noble metal catalysts have been widely used in the petroleum and chemicals processing because of their high activity and selectivity. Optimizing the composition and morphology of catalyst supports could improve the metal dispersion and the metal-support interaction and therefore increase the catalytic performances. In this paper, a series of novel composite composed of carbon nanostructures and layered double hydroxides (LDHs) have been synthesized and utilized as the support for noble metal catalysts. The LDH/C composite maintained the advantages of both carbon nanostructures and LDHs and also exhibited the synergistic effect, which enable it as a promising catalyst support to enhance catalytic performances.In this paper, a Ni-Al layered double hydroxide/graphene (NiAl-LDH/RGO) nanocomposite which was synthesized by introducing NiAl-LDH on the surface of graphene oxide (GO) was utilized as the support for Au nanoparticles. The synthesized Au/NiAl-LDH/RGO catalyst showed preferable catalytic performance including activity, selectivity and stability in the selective oxidation of benzyl alcohol. The activity of Au/NiAl-LDH/RGO catalyst was 9.8 times higher than Au/RGO catalyst and 1.2 times higher than Au/NiAl-LDH catalyst. Improved activity and selectivity was ascribed to the small size of Au nanoparticles which controlled by the defect sites and oxygenic functional groups in RGO and the metal-support interaction benefiting form the surface properties of NiAl-LDH. Moreover, superior catalytic stability of Au/NiAl-LDH/RGO catalyst was attributed to the introduction of NiAl-LDH in the composite support inhibited the aggregation of RGO.Nanocomposites with multi-level structure are widely used in catalysis, adsorption, biomedicine and energy regeneration due to their tunable structure and versatile property. In this paper, a series of LDH@CNS composites with multi-level structure was synthesized by depositing different LDHs on carbon nanospheres (CNS) by coprecipitation. The LDH@CNS composites were utilized as the support for Pd nanoparticles. As comparison, the catalytic performances of both the Pd catalysts supported on LDH@CNS composites and pure LDHs were investigated in the selective oxidation of benzyl alcohol. The activity of Pd/CoAl-LDH@CNS catalyst was 13.1% higher than Pd/CoAl-LDH catalyst, possibly attributing to the flower-like microstructure of the support LDH@CNS could expose more basic sites to contact with Pd nanoparticles. For further investigated the universality of the Pd catalyst supported on composites, Pd/LDH@CNS catalyst was applied in the partial hydrogenation of acetylene and showed preferable catalytic performance including activity and selectivity. Thus, it can be seen that the novel Pd nanocatalysts supported on LDH@CNS composites could be utilized as the high efficient catalysts in both liquid-phase oxidation and gas-phase hydrogenation.