Abstract

CATALYSTS, Chromium; SHOZI, Mzamo L.; ZULU, Xolelwa  and  FRIEDRICH, Holger B.. Ethylene Trimerization over Supported SNS and PNP. S.Afr.j.chem. (Online) [online]. 2021, vol.75, pp.32-39. ISSN 1996-840X.  http://dx.doi.org/10.17159/0379-4350/2021/v75a5.

Chromium(III) complexes with sulphur, nitrogen and phosphorus tridentate ligands were synthesized and characterized. These complexes were supported on SiO₂ and characterized by BET surface area measurements, XRF, SEM-EDX and FTIR. The complexes were tested for activity and selectivity in the trimerization of ethylene. The substituent's effect and influence on the sulphur on the supported catalysts were studied using the ethyl and the decyl substituted catalysts. The influence of temperature on catalytic performance was evaluated using the PPP supported system. The most active supported catalyst, the decyl substituted SNS catalyst, showed good activity of up to 19 500 g/g Cr h^-1 and selectivity of 97.3 % to C6 products (98.2 % 1-hexene). This activity and selectivity were comparable to the homogeneous counterpart's performance that achieved 22 000 g/g Cr h^-1 and 98.2 % C6 products (96.7 % 1-hexene), which surpassed the ethyl substituted catalyst, which was not supported, under the same reaction conditions. The supported PPP catalyst activities showed it was sensitive to higher temperatures, but this depends on the supporting technique.

Keywords : Ethylene trimerization; sulfanyl ligands; phosphine ligands; supported catalysts.

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