Controlled Synthesis And Catalytic Performance Of High Stable And Recoverable Noble Mental Core-shell Catalyst

Noble metal-based catalysts have been widely used in various fields including chemistry,chemical engineering and biological engineering.In recent years,the noble metal nanocatalysts with higher specific surface provide more active sites when compared their bulk ones.They have attracted wide attention due to their high catalytic performances.However,the noble metal nanocatalysts always lost their catalytic activity due to the sintering,aggregation and migration.Moreover,the small particle size results in many problems in recycling noble metal nanocatalysts.Preparing noble metal nanoparticles with core-shell structure can solve these problems mentioned above.The catalytic performance of the noble metal-based nanocatalysts can be greatly enhanced by rationally choosing appropriate shell materials and noble metal nanoparticles.This thesis focuses on the design and preparation of core-shell structured noble metal-based catalysts.Following is the main research contents:?1?The Fe₃O₄@polydopamine-Pt?Fe₃O₄@PDA-Pt?catalyst was prepared by in situ growing platinum nanoparticles on the surface of Fe₃O₄@PDA.The magnetic Fe₃O₄ cores inside the catalyst make the catalyst can be separated by a magnet.Small Pt nanoparticles were uniformly dispersed on the surface of Fe₃O₄@PDA microspheres.The catalytic reduction reactions of nitro phenol?4-NP?and methyl blue?MP?were used as the model reaction to evaluate the catalytic performances,the Fe₃O₄@PDA-Pt catalyst showed high activity,stability and recyclability.?2?The Fe₃O₄/Pd@nitrogen-doped carbon?Fe₃O₄/Pd@NC?catalyst was prepared by coating Fe₃O₄/Pd microsphere with nitrogen-doped carbon shells.The catalytic performances of the Fe₃O₄/Pd@NC catalyst were significantly improved due to the nitrogen-doped carbon shells.The dispersion of Fe₃O₄/Pd@NC catalysts is better than that of commercial Pd/C catalyst in aqueous reaction solutions.the Fe₃O₄/Pd@NC catalyst showed good catalytic activity and recyclability in the reduction reaction of the 4-NP.?3?The magnetically recyclable and high selective Fe₃O₄/Pd@ZIF-8 catalyst with a core-shell structure was successfully synthesized by in situ coating Fe₃O₄/Pd microspheres with ZIF-8 shells.The Pd nanoparticles were uniformly anchored on the Fe₃O₄ support due to the interaction between Pd nanoparticles and amino-modified Fe₃O₄ microspheres.Further coating the Fe₃O₄/Pd microspheres with thin ZIF-8 shells greatly improved the catalytic performances,especially in the catalytic stability and selectivity.The resultant catalyst exhibited excellent size selectivity and magnetic recyclability for the liquid-hydrogenation of alkenes.This study might provide a promising strategy to prepare magnetically recyclable core-shell structured noble metal nanocatalysts with different types of MOF shells.