Preparation of chromium catalysts bearing pyridine based SNS ligands for ethylene trimerization

While conventional ethylene oligomerization reactions generally produce a mathematicaldistribution of LAOs (linear alpha olefins) there has been a considerable interest in the selectiveoligomerization of ethylene to specific carbon chain length olefins. The majority of the knowntrimerization catalysts are chromium-based such as Cr-SNS catalysts that these catalysts are bothhighly active and selective for the ethylene trimerization. In this work we have attention to synthesisand application of two chromium catalysts bearing pyridine and amine based SNS ligands that werenamed respectively as (Cat I) and (Cat II). To synthesize the Cat I, 2,6-pyridine-dimethylene-ditosylate(PMT) as precursor with yield of about 76% was synthesized. Then, octane thiolate was added to aTHF solution of PMT under nitrogen atmosphere at room temperature. After purification with columnchromatography, pyridine based SNS ligand (PMT-Oct) with yield of 60% was obtained. Finally, thePMT-Oct ligand was reacted with CrCl3(THF)3 to produce the Cat I with yield of 61%. For Cat IIpreparation, Bis-(2-octylsulfanyl-ethyl)-amine ligand (Amine-Oct) was reacted with CrCl3(THF)3 atroom temperature. All synthesized materials such as PMT, PMT-Oct and Amine-Oct ligands, Cat I andII were analysed using 1H-NMR, 13C-NMR and CHNS. The activity and selectivity of the preparedcatalysts in ethylene oligomerization reaction under high pressure of ethylene was tested.

کلیدواژه ها:

Ethylene trimerization ، Catalyst ، 1-hexene ، Ligand ، SNS