Controllable Preparation Of Highly Dispersed Au-Pd Catalysts And Their Catalytic Activity For Glucose Oxidation

Gluconate plays an important role in food,industry,medicine and other fields,and one of its main sources is the catalytic oxidation reaction of glucose.The Au catalyst is found to have a high catalytic effect on the reaction,and the reaction conditions are relatively mild,and the process is green and environmentally friendly.However,the reported Au catalysts have poor reaction stability.It is easy to deactivate in the reaction,and its catalytic reaction mechanism is simple,but how to improve the cycle stability still has research prospects.To this end,this paper uses the synergy between the bimetallic active components,studies and improves the preparation method table of the carrier,and uses transition metals to modify the carrier to control the strength of the synergy between the bimetallic components of Au-Pd/Al₂O₃ With the ability of the self-made carrier to absorb and transport oxygen in the catalytic reaction,a series of Au-Pd/AC and Au-Pd/Al₂O₃catalysts with excellent catalytic performance have been successfully prepared,and they have passed XRD,SEM,HADDF-STEM,XPS,O₂-TPD Characterization methods such as FT-IR research and comparative analysis of the structure of the catalyst carrier,the difference in surface composition and the reason for the reduced activity,design and confirm the effect of the synergy between the two metals on the reaction activity,and different supports also have an effect on the catalyst activity.The following conclusions:（1）Designed to use the nano sol method to make Au solution and Pd solution into gold palladium sol,and add commercial activated carbon AC carrier to prepare Au-Pd/AC catalyst,use glucose oxidation reaction as probe reaction.The activity test results show that the catalytic activity mainly depends on the level of Au content,and its cycle stability is also improved compared with single metal Au or Pd catalysts.Further research shows that the Au-Pd bimetallic alloy catalyst was successfully prepared by the nano-sol method.The Au-Pd/AC catalyst has a very high degree of dispersion of Au NPs,with an average particle size of 2.47±0.41 nm,and exhibits extremely high glucose Catalytic oxidation activity,the highest activity can reach 11840 mol_glucose mol _Au^-1 h^-1,and the selectivity of Au-Pd catalyst to glucose oxidation reaction is close to 100%;in addition,the improvement of Au-Pd catalyst activity is mainly due to Au,Pd There is a strong synergistic catalytic effect between bimetals.XPS shows that Pd atoms tend to be positively charged,which leads to stronger interactions between Pd atoms and nucleophilic reactant molecules（such as oxygen molecules）,thereby improving the catalytic activity of the Au-Pd bimetallic alloy catalyst.（2）Based on the research of Au-Pd/AC catalyst prepared by nanosol method,explore the strategies of adopting suitable surface metal oxidation support and improving the preparation method of the support,regulating the preparation of highly dispersed Au-Pd bimetallic alloy catalyst and studying its synergistic catalysis effect.The results show that the Al₂O₃ material synthesized by the deposition-water vapor method is used to replace the activated carbon AC material,and the Au-Pd sol is supported on the Au-Pd/Al₂O₃ catalyst to prepare the Au-Pd/Al₂O₃ catalyst.It is applied to the glucose oxidation reaction and the different raw material ratios and ratios are systematically studied.The effect of Al₂O₃prepared by different calcination temperatures and Al₂O₃ prepared by transition metal doping on the catalytic performance of alloy catalysts.The experimental results show that:Compared with Au-Pd/AC,although the self-made Al₂O₃ has a relatively low specific surface area,the self-made Al₂O₃ catalyst has higher initial reaction activity(16493mol_glucose mol _Au^-1 h^-1),and its cyclic reaction Stability is better.O₂-TPD characterization analysis shows that compared to Au/Al₂O₃ catalyst,Au-Pd/Al₂O₃ catalyst has a stronger ability to adsorb and activate oxygen,which is likely to be one of the main reasons for its higher catalytic reaction rate.（3）The use of transition metal to modify the support,by adjusting the ability of the support surface to adsorb activated oxygen,is another strategy in this paper to further regulate the synergistic catalytic effect between the Au-Pd bimetallic components.Using different transition metal oxides doping to prepare self-made Al₂O₃ surface,exploring and preparing a series of bimetallic alloy catalysts,and used in the glucose oxidation reaction.The experimental results show that:compared with Au-Pd/AC,this series of catalysts also have higher initial reaction activity,and its cyclic reaction stability is better.However,not all transition metal oxides can increase the reaction rate of the catalyst.Only the introduction of Ni,Mg and other metals can promote the oxidation reaction of glucose.This may be because the self-made Al₂O₃ surface has abundant surface hydroxyl groups.The introduction of metal oxides is related to the destruction or consumption of the hydroxyl groups of alumina,and relevant research is still continuing to explore.