Inorganic supports polymerization

There is a whole spectrum of heterogeneous catalysts, but the most common types consist of an inorganic or polymeric support, which may be inert or have acid or basic functionality, together with a bound metal, often Pd, Pt, Ni or Co. Even if the support is inert its structure is of vital importance to the efficiency of the catal ic reaction. Since the reactants are in a different phase to the catalyst both diffusion and adsorption influence the overall rate, these factors to some extent depending on the nature and structure of the support. 

Cyanide complexes have a venerable history (see CCC S )),1 and find utilization in many industrial processes including as synthetic catalysts e.g., Co cyanides on inorganic supports catalyze alkylene oxide polymerization,187 molecular magnetic materials, in electroplating, and in mining. Their pharmacology and toxicology is well explored... 

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). 

We now present several useful, or potentially useful, systems based on luminescent metal complexes in organic or inorganic supports. The probe molecules were chosen based on the above guidelines. Each probe is supported in some way by a second material to produce a practical device. The results presented show how metal complexes can be applied to diverse problems. These results also identify some problem areas with polymeric supports. We discuss some of our insights into the design and modeling of such systems and describe measurements that help unravel these complex systems. 

Polymerization activity was markedly enhanced when the catalysts were chemically grafted onto inorganic supports. Typical results are... 

Owing to the heat capacity of the catalyst support (this holds especially true for inorganic supports) overheating is avoided particularly in the early stages of the polymerization after the supported catalyst is introduced to the gas-phase reactor. Another approach is taken by UCC who describe the use of catalyst solutions rather than supported catalysts. In the UCC-approach catalyst solutions are injected into the gas-phase reactor and the polymerization heat is removed by evaporation of the solvent [560-563]. 

In terms of availability, number, and nature of surface groups, surface area, pore size, pore volume, and form and size of the particles, silica has been undoubtedly the most preferred inorganic support. Suitable modification is possible via the surface silanol groups, which can react either directly with an appropriate metal complex or with an intermediate ligand group. Direct surface bonding has often been practiced, e. g., for the anchoring of metal carbonyl complexes [14] (eq. (11)), carbonyl clusters [26], polymerization catalysts [21, 62], or other special systems, e. g., 7r-allyl complexes [63] or metalloporphyrins [64]. 

Insoluble chiral catalysts bearing stationary supports such as inorganic materials or organic crossUnked polymers, or homochiral organic-inorganic coordination polymeric catalysts without using any external support. 

Although the inorganic supports show many advantages such as temperature stabihty, solvent, and mechanical resistance, there are not many papers dealing with the use of these membranes for SLM construction, probably due to the same problems as for polymeric supports membrane stabihty and lifetime. 

V(L)Cl2(TpMs )] (L = N Bu L = O) were in situ supported onto SiC>2 and onto MAO and trimethylaluminum. All catalyst systems were shown to be active in ethylene polymerization. The systems were stable at different [A1]/[V] molar ratios and polymerization temperatures.21 Branched polyethylene/high-density polyethylene blends were prepared using the combined [NiChfa-diimine)] and V(T(Tp-vls )(N Bu) catalysts. The polymerization reactions were performed in hexane or toluene at three different polymerization temperatures (CPC, 30°C and 50°C) and several nickel molar fractions, using MAO as cocatalyst.22 TpMs- and TpMs -imido vanadium (V) were immobilized onto a series of inorganic supports All the systems were shown to be active in ethylene polymerization in the presence of MAO or TiBA/MAO mixture.23... 

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