Heterogeneous reagent/catalyst immobilization

In addition, immobilization of active metal components on the support materials with the aid of ILs provides the following features (i) stabilization of the metal catalysts on the surface of the supports, (ii) use of small amounts of IL, and (iii) accumulation of metals on support materials to facilitate catalytic reactions. As a result, the heterogenization of catalysts and reagents can offer important advantages in separation and reuse. 

In order to overcome these problems, attention was focused on the use of heterogeneous catalysis. We have found that functionalized solid materials, e.g., ionic liquids or tin triflates immobilized into mesoporous materials, can be used in N-acylation reactions as environmentally friendly replacements for traditional homogeneous acids which are useful but environmentally unacceptable catalysts [17, 18]. They had comparable activity to homogeneous reagents but can offer greater stability, safer and easier handling and can be... 

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). 

Oxidation of alcohols to carbonyl compounds is an important reaction. Stoichiometric oxidants such as chromates, permanganates and MO4 (M = Ru, Os) are the commonly used reagents [19a,59,60]. However, they are going out of favour increasingly because they create heavy metal wastes . In view of this, development of environmentally friendly heterogeneous catalysts for alcohol oxidation is very important. In the use of catalytic amounts of transition metal salts or complexes as homogeneous catalysts for the oxidation of alcohols [61-64], separation of the catalyst from the reaction mixture and its subsequent recovery in active form is cumbersome. Heterogeneous catalysts for this kind of reaction are therefore necessary [65]. Clearly, encapsulation and/or immobilization of known... 

Heterocycles as reagents and ligands in immobilized heterogeneous catalysts 95MI1. 

There have been many approaches published to "immobilize" a homogeneous catalyst. These heterogeneous catalysts must have better activity, selectivity, lifetime or some other property to warrant their use in an industrial chemical process. This talk will draw upon the author s experiences at DuPont and Air Products with Nation , Nafion on carbon, anionic attached [Rh(CO)2l2] to Reillex-425, carbons as catalysts for the hydrolysis of esters, heterogeneous catalyst to activate dimethyl ether as a methyl transfer reagent, and monoliths as hydrogenation catalysts. These individual experiences will show the complexities of a simple problem - "immobilization". 

---