Clay as a Polymerization Catalyst Support

Ray et al. [24] treated Cloisite 20A (montmorillonite modified with dimethyl-ditallow-containing approximately 65% Cig, 30% Cis, and 5% Ci4-ammonium cation chains) with a MAO solution, after vacuo-drying at 100 °C. The resulting MAO-treated clay was subsequently used for ethylene polymerizahon in the presence of a late transition metal catalyst (2,6-bis[l-(2,6-diisopropylphenylimino)ethyl] pyridine iron(ll) dichloride) and additional MAO in a glass reactor. They compared the result with homogeneous polymerization with the same catalyst in the presence of Cloisite 20A and observed that the supported catalyst was more efficiently exfoliated than when only a mixture of catalyst and clay was used. This comparison led them to conclude that at least some of the active centers resided within the clay galleries. Inductively coupled plasma (ICP) measurements showed that all MAO and catalyst remained in the solid catalyst after drying. 

Sample Clay (g/L) Added MMAO (mol L g- ) Supported/ added MMAO (%) Added CpaZrCb (x10 molL- g ) Supported/ added CpaZrCh (%) 

The authors considered this organic modification removal as a result of reactions between oxygen atoms in MMAO and ammonium ions. They also compared three different in-situ polymerization methods performed under atmospheric pressure of ethylene  

1) polymerization in the presence of MMAO-modified clay (MMAO/clay + catalyst)  

2) polymerization with catalyst supported on MMAO-modified clay (or MMAO/ clay/catalyst), with additional MMAO  

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