ChemInform Abstract: HYDROGENATION OF OLEFINS AND POLYMERIZATION OF ETHENE OVER CHROMIUM OXIDE/SILICA CATALYSTS. III. HYDROGENATION OF OLEFINS AND HYDROGEN/DEUTERIUM EXCHANGE

Wittgen, P.P.M.M.; Groeneveld, C.; Zwaans, P.J.C.J.M.; MORGENSTERN, H. J. B.; Heughten, A.H. van; Heumen, C.J.M. van; Schuit, G.C.A.

doi:10.1002/chin.198308085

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“…This study shows that heterolytic C-H activation of ethylene is likely a key step in ethylene polymerization, a mechanism that conserves the Cr-oxidation state during catalysis. Heterolytic C-H activation is common on supported metal species, and is probably a key step in alkane dehydrogenation using Cr(III)/Al 2 O 3 catalysts [31], C-H activation on alumina surfaces [32][33][34], hydrogenation reactions involving supported chromium species [35], and in ethylene polymerization on well-defined Cr(III)-silicates [15]. In addition, the presence of Cr(III) sites according to EPR and the striking similarity of the IR Fig.…”

Section: Discussionmentioning

confidence: 99%

Polymerization on CO-Reduced Phillips Catalyst initiates through the C–H bond Activation of Ethylene on Cr–O Sites

Delley¹,

Conley²,

Copéret³

2014

Catal Lett

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Investigation of the polymerization of ethylene on CO-reduced Phillips catalyst (1 wt% chromium) by infrared spectroscopy reveals the presence of new OH bands. In particular, an OH-band appears at 3,605 cm-1 , consistent with the interaction of the SiOH group with an adjacent Lewis acidic chromium center, Si-(l-OH)-Cr. Polymerization with d 4-ethylene leads to the formation of the isotopically shifted band at 2,580 cm-1 , consistent with heterolytic C-H activation of ethylene over a Cr-O bond to generate the first Cr-C bond in ethylene polymerization with Phillips catalyst, as recently observed on well-defined Cr(III) silicates.

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