Recent work on the longstanding mystery of ethylene-induced initiation in the Phillips catalyst includes progress at several different scales.  At the molecular scale, calculations show that initiation can occur via conversion of a bis(ethylene)Cr(II) complex to chromacyclopentane which then homolyzes one of its two Cr-C bonds. While remaining attached to the metal through its other Cr-C bond, the dangling radical attacks a nearby Cr(II) site. The result is two activated Cr(III) sites capable of Cossee-Arlman polymerization, and the overall pathway has a barrier of 133 kJ/mol.  These results are approximately consistent with experimental initiation times at industrial loadings, and with new data on induction times at different Cr-loadings.  I will discuss our theoretical efforts to compute site averaged kinetic properties for these atomically dispersed catalysts on quench-disordered silica. <br/>

Toward an understanding of initiation in the Phillips catalyst

256th National Meeting (2018)

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