Research On Microstructure Regulation And Catalytic Performance Of Supported Noble Metal Catalysts With High Stability

As the most important component of heterogeneous catalysts,the supported noble metal catalysts are widely used in some fields such as organic synthesis,car exhaust gas purification and fuel cell.The highly dispersed noble metal particles are the key to ensuring the catalytic activity of catalysts,however,their catalytic activity would be lost due to the migration and growth of the noble metal particles at high temperature.Therefore,this paper addresses the problem by designing the structure of the catalyst supports to form geometric confinement on noble metal particles and regulating the interaction between the noble metal particles and the support to improve the sintering resistance of the noble metal catalysts.This work provides new ideas and approaches for the further development of the supported noble metal catalysts.The main research contents and results are as follows:The ZrO₂ hollow spheres are prepared by sacrificing template method,in which Pd nanoparticles are anchored to the inner wall of the hollow spheres.The rich mesoporous structure in the sphere wall enables the full contact between the reactants and active sites,thereby facilitating the reaction.Compared with the Pd/ZrO₂ catalyst in which Pd particles are directly loaded on ZrO₂ particles,the Pd@HS-ZrO₂catalyst exhibits high activity and thermal stability even when calcined at 800℃.The Pd particles also maintain good monodispersity at high temperature.The above results fully demonstrate the structural advantages of ZrO₂ hollow spheres.With the ability of polydopamine（PDA）to chelate metal ions,the Au/γ-Al₂O₃ is coated to prepare Au/γ-Al₂O₃@CeO₂ catalysts with high activity and stability.The dopamine molecules not only act as structural guider to form PDA-Ce coating layer on the surface of Au/γ-Al₂O₃,but also act as pore-forming agent to obtain porous structure in CeO₂ layer after in-situ oxidation during high temperature calcination.Therefore,the Au particles can fully expose the active sites while being confined.And the modification method was effectively extended to the Pd/γ-Al₂O₃ catalyst.By the reversible process of Mg（OH）₂（?）MgO+H₂O,the decomposition of Mg（OH）₂ at high temperature under inert atmosphere could activate the surface of support to construct strong metal-support interaction（SMSI）between Au and MgO to prepare Au/MgO catalysts with high activity and stability.The MgO coating layer could effectively inhibit the migration of Au particles at high temperature.Compared with the Au/MgO-O₂ catalysts calcined in air without SMSI formation,Au/MgO-Ar exhibits higher catalytic activity and thermal stability.