Preparation Of Gold And Cerium Oxide Composite Material And Its Catalytic Performance For Oxidative Esterification Of Aldehydes

Methyl methacrylate（MMA）is an important fine organic chemical widely used in plexiglass,medicine,adhesives and other fields.Gold catalyst has excellent catalytic performance in catalyzing the oxidative esterification of methacrolein（MAL）and methanol（Me OH）,but the life of the gold catalyst is also a key factor in evaluating its catalytic performance.There are two main reasons for the deactivation of gold catalysts:（i）gold particles are easily lost after a long time of use,resulting in decreased activity or deactivation;（ii）the growth of gold particles leads to the decrease or even deactivation of the catalytic activity.Therefore,it is of great significance to prepare a long-lived gold catalyst.In this thesis,we prepared highly dispersed single-atom gold catalysts and core-shell gold catalysts,investigated their oxidative esterification properties for catalyzing MAL to MMA,and carried out kinetic analyses.The main research contents are as follows:1.Single-atom Au catalysts with different Au loadings were synthesized and applied for the oxidative esterification of MAL and Me OH.The catalysts were characterized by XRD,TEM,BET,ICP and UV-vis.The reducibility of the catalysts was tested by H₂-TPR.Ce O₂ carrier distribution,electronic states of O and Au,and between Au and Ce O₂ and the active oxygen on the surface of the Ce O₂ carrier was studied by XPS.The cycle performance of the Au-10/Ce O₂ catalyst was examined,and the single-atom Au-10/Ce O₂ catalyst with the best catalytic performance was selected,a kinetic analysis was carried out after eliminating the influence of the internal diffusion and external diffusion in the reaction,and the activation energy of the reaction was calculated.Through experimental research,it is found that the highly dispersed single-atom gold catalyst has more active sites and thus has a higher activity without increasing the gold loading,and the single-atom gold anchored on the Ce O₂ support is not easy to lose It is easy to agglomerate to improve the service life of the catalyst.2.A series of highly stable Au@Ce O₂/Mn O_x core-shell catalysts were synthesized and applied for the oxidative esterification of MAL and Me OH to prepare MMA.The catalysts were characterized by XRD,Raman,BET,TEM,FT-IR,ICP and UV-vis.The reducibility of the catalyst was tested by H₂-TPR.The role with the interaction between Au and Ce O₂and the active oxygen on the surface of the Ce O₂ carrier was studied by XPS.The Au@Ce O₂-C-10 catalyst with the best catalytic performance was selected to test the cycle performance.After eliminating the influence of the internal and external diffusion of the reaction,a kinetic analysis was carried out and the activation energy of the reaction was calculated.In conclusion,The Au@Ce O₂ core-shell structure could prevent the agglomeration of gold,thereby prolonging the service life of the catalyst.