Preparation Of Nanodiamond Supported Pd Catalysts And Their Catalytic Performance

Benzaldehyde is an important chemical product which is widely used in the synthesis of medicines,spices,pesticides and dyes.Traditional methods for the preparation of benzaldehyde such as chlorination-hydrolysis of toluene often lead to serious equipment corrosion and environmental pollution.Therefore,the development of a green and environmentally friend ly oxidation process of benzyl alcohol has become a hot topic for researchers.As a special carbon material,nanodiamond is ascending in the field of catalysis due to the characteristics of both diamond and nano materials.The high-defect graphene on the surface of nanodiamond after calcination can provide anchor sites for metal nanoparticles?NPs?which prevents the metal NPs from aggregating.By oxidizing graphitized nanodiamonds,the introduced oxygen-containing functional group interact with the metal,thereby improving the catalytic activity of the prepared catalyst.Therefore,it is of great research value to explore a green and efficie nt graphitized nanodiamond supported palladium catalyst for selective-oxidation of benzyl alcohol.?1?Firstly,nanodiamonds with different graphitization extents were calcined at 700?,900? and 1100?,respectively,followed by the impregnation of Pd²⁺and further reduction process,which were applied on selective-oxidation of benzyl alcohol.The structure of support and active components of the catalyst were studied by TEM,XRD,Raman and XPS.Comparing the catalytic activity of the nanodiamond treated at different temperatures supported palladium catalysts,the nanodiamond-graphene core-shell structure obtained by calcination at1100? supported palladium?Pd/ND@G-1100?showed the best catalytic activity.After optimizing the reaction conditions,the specimen with Pd loading of 3 wt%exhibited the optimum results that the conversion of benzyl alcohol reached 42.6%and the selectivity of benzaldehyde reached 82.2%,with the catalyst amount of 50 mg?9?_{benzyl alcohol}?9)_?9?=1940,under the reaction temperature of 115? and reaction time of 3.5 h.?2?Pd/ND@GO was designed and synthesized through impregnation method to anchor Pd NPs on nanodiamond-graphene oxide?ND@GO?obtained from ND@G by nitric acid treatment,which was applied to selective-oxidation of benzyl alcohol.TEM,XRD,IR and XPS were used to characterize the morphology and structure of this material.Simultaneously,the effect of the oxygen content of Pd/ND@GO on the catalytic activity was studied.When the oxidation time with nitric acid was 6 h and the mass concentration of nitric acid was 58%,Pd/ND@GO-1100 exhibited marvelous catalytic activity with the conversion rate of benzyl alcohol and the selectivity of benzaldehyde reaching 100%,and 94%,respectively,with the catalyst amount of 50 mg?9?_{benzyl alcohol}?9)_?9?=2186,under the reaction temperature of115? and reaction time of 3.5 h..