Costruction Of Au Catalysts Based On Layered Double Metal Hydroxide/Carbon Nanocomposites And Their Catalytic Oxidation Properties

Biomass resources are attracting attentions as the most promising alternative to fossil resources for the depletion of fossil resources and environmental problems that are urgently needed to be addressed.The path of biomass conversion is the conversion of biomass degradation into platform molecules,which are then catalytically converted into high value-added chemicals.The catalytic conversion of platform molecules requires high performance catalysts.Benzyl alcohol(BA)and 5-hydroxymethylfurfural(HMF)are widely used as intermediates in the synthesis of various fine chemicals as a biomass platform compound.Therefore,it is of practical significance to develop a highly efficient alcohol oxidation catalyst for biomass platform compounds.In this paper,LDHs and treated carbon materials(N-CDs or acidified-CNTs)were used as composite carriers,and Au nanoparticles were loaded by NaBH4 immersion reduction method and resulting the formation of two new Au-based solid base catalysts.The as-prepared catalysts were is applied to the aerobic oxidation reaction of benzyl alcohol to a benzaldehyde under solvent-free condition and the selective oxidation reaction of 5-hydroxymethylfurfural to FDCA.The detailed work is as follows:(?)Nitrogen-doped carbon materials(N-CDs)were successfully prepared by solid phase heat treatment of DCD and CA.N-CDs/MgAl-LDHs composite carrier was prepared by double-drop method,and Au nanoparticles were loaded by NaBH4 reduction method,obtaing Au/NCDs/LDHs solid base catalyst.The effects of alkaline synergy of hydrotalcite and nitrogen-doped carbon materials on the catalytic performance of the composite support were invostigated by characterization and performance tests.It is well known hydrotalcite has a certain Bronsted basicity,and N-CDs surface provides Lewis basic sites.there are synergistic effect of B base and L base in the composite support.Becaue the presence of basic site can adsorb and activate the alcoholic hydroxyl group of benzyl alcohol to form alkoxy intermediate.Therefore,the presence of N-CDs and the alkaline synergy of hydrotalcite and nitrogen-doped carbon materials make the catalyst exhibits excellent catalytic performance.The results show that the reaction temperature is 120?,the reaction time is 1 h,the oxygen pressure is 0.4 MPa,the TOF value reaches 20175 h-1,and the Au/N-CDs/LDHs composite exhibits excellent catalytic activity,stability and recyclability.The catalytic performance of Au/N-CDs/LDHs composites has significant advantages compared with the catalysts of the same literatures,showing good application prospects.Based on the results of catalytic experiments,the mechanism of selective oxidation of benzyl alcohol in the absence of alkali and solvent was discussed.(?)A composite of hydrotalcite and acidified carbon nanotubes(LDHs/CNTs)was used as a carrier,and Au nanoparticles were loaded by NaBH4 reduction method to prepare a highly efficient and stable catalyst Au/LDHs-CNTs.The Au/LDHs/CNTs catalyst was applied to the aerobic oxidation of HMF in an aqueous phase without alkali,showing high and stable catalytic activity.The effects of different mass ratios,reaction temperatures and reaction times of LDHs and CNTs on the selective oxidation of HMF were investigated.The catalyst with the best LDHs and CNTs initial ratio was tested for catalyst activity,stability and reusability.The results showed that HMF was almost completely converted to FDCA under the reaction conditions of 150? and 6 h;the catalyst with optimum LDHs and CNTs inital ratio showed acid resistance,high stability and high activity.