Metallocenes/operation catalyst activators

The process operates in the liquid phase by dissolving the ethylene in an inert solvent such as cyclohexane or isopentane. The metallocene catalyst is also injected to the mix. The solvent has several important functions. It keeps in solution the alpha olefins produced as well as the ethylene and catalyst. It also enhances the catalyst activity and selectivity. 

Several important homogeneous catalytic reactions (e.g. hydroformylations) have been accomplished in water by use of water-soluble catalysts in some instances water can act as a solvent and as a reactant for hydroformylation. In addition, formation of aluminoxanes by partial hydrolysis of alkylaluminum halides results in very high activity bimetallic Al/Ti or Al/Zr metallocene catalysts for ethene polymerization which would be otherwise inactive. Polymerization of aryl diiodides and acetylene gas has recently been achieved in water with palladium catalysts. Finally, nickel-containing enzymes, such as carbon monoxide dehydrogenase (CODH) and acetyl-CoA synthase, operate in water with reaction mechanisms comparable with those of the WGSR or of the Monsanto methanol-to-acetic-acid process. ... 

These processes have been used successfully for many years to carry out gas-phase polymerization of polyolefins using the Ziegler-Natta catalysts. It was expected that replacement of the Ziegler-Natta by metallocene catalysts in fluidized-bed reactors will be rather straightforward. However, the adaptation of the more active metallocenes to existing commercial fluidized-bed reactors led to many operational problems. For... 

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