Supported transition metal complex catalysts selectivity

Pis serve as catalysts for transition metal complexes. These metal eom-plexes are suitable for the epoxidation of olefins. The heterogeneous PI-supported transition metal complex catalysts provide superior catal5dic activity, selectivity and stability in the epoxidation of higher olefin. Because of the heterogeneous nature, the catalysts can be easily separated from the reaction product, which eases recycling of the catalysts." ... 

Another example of coordination of a transition metal into a selected polymer is the use of Nafion resin [7]. Several studies over the past 20 years have demonstrated that the perfluorinated ion-exchange polymer is an excellent support for metal-complex catalysts (Figure 11.1). 

Many heterogeneous catalysts have been reported in the past to be prepared by anchoring or grafting, processes whereby stable, covalent bonds are formed between an homogeneous transition metal complex and an inert polymer or inorganic support [1-4] The aim was to combine the potential versatility and selectivity of homogeneous catalysts with the practical advantages of a solid material [5]... 

The catalytic activity of zeolites in alkane to olefin reactions, photochemical conversion reactions, Fischer-Tropsch hydrogenation, isocyana-tion, carbonylation, and related chemistry make up the last theme. An important focus of this is to explore the utility of zeolites as selective heterogeneous catalysts for reactions that involve Group VIII metals. The mechanistic nature of some of this chemistry is presented, along with the characterization of supported organometallic transition metal complexes. 

A new type of materials has been developed by delaminating the lamellar precursors of some zeolites. These materials show external surface areas > 600 m. g from where active sites can be accessible to very large molecules. If on one hand delamination eliminates geometrical shape selective properties of zeolites, it allows on the other hand to dispose of catalysts with the good reactant accessibility of mesoporous materials, but with the stability and active sites characteristics of zeolites. The very large and well structured external surface area can be specially suited for supporting different catalytic functions, which include, among others, metals, transition metal complexes and enzymes. 

Very recently a critical review of the work on heat-treated macrocylic complexes on carbon was published It showed that the results for gas diffusion electrodes obtained can hardly be compared with each other. The activity and pyrolysis behaviour of carbon-supported transition metal chelates is determined by various factors such as the chelate, the texture of the carbon, the dispersion of the catalyst on the support, the kinetics of the pyrolysis reactions, etc. The processes which occur during the metal loading on the carbon and the pyrolysis were discussed. The authors developed a new carbon modified rotating ring disc electrode which can be used for quick comparisons of both the activity and selectivity of carbon-supported catalysts... 

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