Supported Catalysts Coated with Shell Layers

4 Supported Catalysts Coated with Shell Layers 

The construction of core- or yolk-shell nanoarchitectures relies on the encapsulation of an individual metal NP with a shell layer. As demonstrated in the above examples, these catalysts were effective as nanoscale model catalysts that show thermal and chemical stabilities, as well as enhanced catalytic activity and selectivity. Recent works demonstrated that the principles acquired from these model catalysts are applicable to more complex model catalytic systems, and even to industrial supported catalysts. 

Asefa and his co-workers coated a silica layer on a silica sphere-supported Pd catalyst (Pd/Si02), followed by partial etching of the outer silica layer using NaOH, 

Nanocryslal htanocrystal Cu20 E(ched-Cu20 ZIF-8 Nanocrys(al ZIF-8 

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Among other things, Pd-Au coated catalysts are extremely well suited to the catalysis of the gas phase oxidation of ethylene and acetic acid to give vinyl acetate. The catalytically active metals are deposited in the form of a shell on or in the outermost layer of the support. They are often produced by penetration of the support with metal salts into a surface region and subsequent precipitation by alkalis to form water insoluble Pd-Au compounds (5). 

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