Solid catalysts and reagents

Many books and reviews cover the preparation, characterization4 and use of homogeneous5 and heterogeneous6 catalysts. Others describe supported metal catalysts,7 other supported catalysts and reagents,8 and their use in preparative chemistry,9 the use of polymers as supports,10 trends in industrial catalysis,11 and the environmentally friendly nature of solid catalysts and reagents.12... 

J. H. Clark and C.N. Rhodes, Clean Synthesis Using Porous Inorganic Solid Catalysts and Supported Reagents , Royal Society of Chemistry, Cambridge, 2000. 

Recyclability can be achieved by heterogenization of the reaction mixture, by binding the catalyst and products to different phases. This can be achieved by (i) immobilization of the catalyst on a solid inorganic or polymeric support (solid-liquid protocols) or (ii) partitioning the catalyst and reagents/products in different liquid phases (liquid-liquid protocols) (see Chapter 9.9 for more details on supported catalysts). 

Clark, J. H. Rhodes, C. N. Clean syntheses using porous inorganic solid catalysts and supported reagents, Royal Society of Chemistry Cambridge, UK, 2000. 

Recyclable Catalysts and Reagents and Solid-Phase Synthesis... 

Catalytic reactions take place by individual molecular interactions at active sites. These sites, specifically favorable to reaction, exist only at the interface between solid catalyst and some fluid phase that conveys reagent species and exports products of catalytic reaction. Usually, to achieve practical reaction rates, any catalytic agent should be deployed over a large surface area. This is facilitated by dispersing the catalyst within some support solid. Other components, like binders and promoters, may also be incorporated to enhance reactivity. 

Reaction of dialkylmagnesium compounds with selected chlorinated compounds produces finely divided MgCl that can be used as a support for polyethylene catalysts. Other reagents may be used to produce different inorganic magnesium compounds, also suitable as supports. Examples are shown in Figure 4.1. Treatment of these products with transition metal compounds results in a supported "precatalyst." Typically, the transition metal is subsequently reduced by reaction with an aluminum alkyl and the solid catalyst isolated. The solid catalyst and cocatalyst (usually TEAL) may then be introduced to the polymerization reactor. 

Thus, irrespective of the order of addition of the catalyst and reagents for the solid-phase catalytic hydrosilylation reaction to proceed, the appearance of an active intermediate compound containing both of the reagents and catalyst is necessary ... 

Clean Synthesis Using Porous Inorganic Solid Catalysts and Supported Reagents... 

Many reactions in the fine-chemical industry are performed with organic liquids or in organic solvents. When the surface of a solid-acid catalyst is hydrophilic, the presence of small amounts of water can completely block the surface of the catalyst. Carefully dried catalysts and reagents must then be employed. It may be noted that zeolites with a high silica-to-alumina ratio are hydrophobic. The (internal) surface of the zeolite is, therefore, not readily poisoned by accumulation of (traces of) water. With zeolites, moreover, use can be made of the uniform size of the pores to perform shape-selective reactions after passivation of the catalytic sites on the external surface of the zeolite crystallites. In the bulk-chemical industry several interesting reactions have been developed with zeolite catalysts [27] (cf. the review of Tanabe and Hdlderich [28]). 

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