The Synthesis Of PtPdNi Ternary Metal Nanocatalyst And Its Catalytic Performance For The Hydrogenation Of Benzaldehyde And Styrene

Metallic catalysts are widely used in the field of heterogeneous catalysis,such as,catalytic oxidation,catalytic hydrogenation,and electrocatalysis.The type of metallic catalysts has gradually changed from the mono-metallic to the multi-metallic catalysts.How to enhance the catalytic performance（activity,selectivity and stability）of multi-metallic catalysts and the utilization of noble metal has become a crucial problem.This work designed the PtPdNi tri-metallic nanocatalysts,their catalytic hydrogenation performance and utilization of noble metal were improved by the synergistic effect of relevant species and the interaction between the metal and support.The main research results of this paper were as follows:（1）Platinum（Pt）,palladium（Pd）and nickel（Ni）were used as the active sites,which were supported on the faujasite（FAU）,multi-walled nanotubes（CNTs）and black carbon（BP-2000,C）,a series of mono-metallic and multi-metallic supported catalysts with different metal compositions were prepared.Benzaldehyde and styrene hydrogenation reactions were used as model reactions to explore their different catalytic hydrogenation performance and its reason was investigated.The X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,high-resolution transmission electron microscopy（HRTEM）,High-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）,energy-dispersive X-ray spectroscopy（EDS）elemental mapping and line-scanning,high sensitivity low energy ion scattering（HS-LEIS）and H₂-temperature programmed reduction（H₂-TPR）were used to characterize the nanostructures and other properties of the as-prepared catalysts.（2）The Pt-Pd nanoalloy clusters could improve bezaldehyde hydrogenation.Under the mild reaction conditions（25°C and 1 MPa H₂）,the turnover frequency(TOF=7801.8 h^-1)of the 1.5%Pt-1.5%Pd/Ni/FAU tri-metallic catalyst for benzaldehyde hydrogenation was6.7 times as much as 3%Pt/Ni/FUA,and 23 times as much as 3%Pd/Ni/FAU.When C was used as support,the catalytic performance of the 1.5%Pt-1.5%Pd/Ni supported catalysts for benzaldehyde hydrogenation was better than that of the 3%Pt/Ni and 3%Pd/Ni supported catalysts.The characterization results confirmed the reasons were that the Pt-Pd nanoalloy clusters formed in the 1.5%Pt-1.5%Pd/Ni tri-metallic catalyst and the interaction between Pt and Pd,which could improve the catalytic hydrogenation activity for benzaldehyde hydrogenation.The catalytic hydrogenation activity of the tri-metallic catalysts with 1%and0.1%loading of noble metals（Pt+Pd）was between the PtNi and PdNi bimetallic catalysts because the Pt-Pd nanoalloy clusters did not completely form and thus the interaction between Pt and Pd was weak.The promoting effect of the Pt-Pd nanoalloy clusters was not obvious for the hydrogenation of styrene.（3）When FAU was used as supported,the presence of Ni increased the catalytic activity of the catalysts for benzaldehyde and styrene hydrogenation reaction.The 1.5%Pt-1.5%Pd/Ni/FAU catalyst（uncalcined）provided TOF of 12300 h^-11 and 45648 h^-1 for the hydrogenation of benzaldehyde and styrene,respectively,which was higher than 1.5%Pt-1.5%Pd/FAU catalyst.It suggested that Ni improved their catalytic hydrogenation activity.It was found that Ni could enhance the dispersion of Pt and Pd by analyzing the characterization results.Thus,the Pt-Pd particles size in the 1.5%Pt-1.5%Pd/Ni tri-metallic catalyst was smaller than that in 1.5%Pt-1.5%Pd/FAU.（4）The catalytic performance of the catalysts with faujasite as support was much more excellent than that of the catalysts with the CNTs and C as support.For example,the average size of metal nanoparticles in 1.5%Pt-1.5%Pd/Ni/FAU was 3.33 nm,which was smaller than that of metal nanoparticles in the tri-metallic catalysts with CNTs（14.86 nm）and C（7.79 nm）as the support,faujasite supported catalysts had micropore structure and it has high thermal stability during being reduced process,thus forming the metal-support interactions.It prevented the Ni nanoparticles agglomerating with better dispersion.Therefore,the catalytic property of the 1.5%Pt-1.5%Pd/Ni/FAU catalyst（uncalcined）for benzaldehyde（styrene）hydrogenation(TOF=12300.8 h^-1 or 45648 h^-1)was much more excellent than that of 1.5%Pt-1.5%Pd/Ni/CNTs（uncalcined）(TOF=900.3 h^-1 or 21052.8h^-1)and 1.5%Pt-1.5%Pd/Ni/C（uncalcined）(TOF=665.9 h^-1 or 21196.8 h^-1)。With FAU as the support,the interaction（between Pt and Pd,Pt-Pd and Ni）in the PtPdNi tri-metallic catalysts promoted catalytic hydrogenation performance.Compared to catalysts with CNTs and BP-2000 as support,the catalysts with FAU as support were with small metal particles size.This work will provide certain theoretical basis for designing and preparing the multi-metallic nanocatalysts with lower noble metal loading,and high stability and excellent catalytic performance for catalytic hydrogenation reactions.