The Synthesis And Evaluation Of Ethylene Tirmerization Catalysts With Multidentate SNS Ligands

In this article,the (C8H17SCH2CH2)2NH and (C14H29SCH2CH2)2NH multidentate SNSligands were prepared at0℃using bis(2-chloroethyl)amine, n-octyl mercaptan andn-Tetradecyl mercaptan as the raw materials,and reacted with CrCl3(THF)3at roomtemperature to give the corresponding SNS/CrCl3catalyst. The structure of two ligands wasrespectively characterized by defferent methods. Both species of ligand were used to ethylenetrimerization to1-hexene. The composing and content of liquid products were analysed bygas-chromatograph. The activity and selectivity of ethylene trimerization were studied undervarious reaction conditions(reaction temperature,ethylene pressure and the amount ofcocatalysts etc.).It was found that an ethylene trimerization reaction at90℃and5MPa ethylenepressure, using the CrCl3(THF)3/(C8H17SCH2CH2)2NH complex activated by300equivalents of MAO, afforded97.43%1-C6. Only0.35%PE was produced and the catalystactivity was55.94kg/gCr·h-1.Using the CrCl3(THF)3/(C14H29SC2H4)2NH complex activated by300equivalents ofMAO at90℃and5MPa ethylene pressure,afforded98.57%1-C6. Only0.26%PE wasproduced and the catalyst activity was87.70kg/gCr·h-1.Comparison of two catalytic system found that the CrCl3(THF)3/(C14H29SC2H4)2NH/MAO system has higher catalystic activity and selectivity for ethylene trimerization than theCrCl3(THF)3/(C8H17SCH2CH2)2NH/MAO system.It may be due to the enhanced solubilityin solvent that the longer alkyl chain of sulfur-substituted affords. Both of them, coupled withthe high activity,excellent selectivity, and performance in the presence of low amounts ofMAO, means that the potential of the systems being employed to produce1-hexene on a largescale is promising.