1887

oa Litnet Akademies : 'n Joernaal vir die Geesteswetenskappe, Natuurwetenskappe, Regte en Godsdienswetenskappe - Oligomerisasie van langerketting 1-alkene in die teenwoordigheid van Cp2MCl2-metalloseen-, meer komplekse Zr-metalloseen- en tridentaat bis(imino)piridienyster(II)-katalisatorsisteme

Volume 15 Number 3
  • ISSN : 1995-5928

 

Abstract

Die oligomerisasievermoë van ’n reeks Cp2MCl2-metalloseen- (Cp = siklopentadiëniel, η5-C5H5; M = Zr, Ti, Hf en Nb), meer komplekse Zr-metalloseen- en tridentaat bis(imino)piridienyster(II)- katalisatorsisteme is ondersoek. Verskeie faktore wat die katalisatoraktiwiteit van die Cp2MCl2- metalloseen-katalisatorsisteme gedurende die omskakeling van 1-alkene kan beïnvloed, is nagegaan. Die faktore is: aktiveringstemperatuur (Ta), aktiveringstyd (ta), reaksietemperatuur (Tr), kokatalisatorkonsentrasie, die tipe oorgangsmetaal (M) en die monomeerkonsentrasie (mo). Die temperatuur, die oorgangsmetaal en die kokatalisatorkonsentrasie het die reaksietempo en die graad van oligomerisasie dramaties beïnvloed. Die twee faktore wat die reaksietempo en graad van oligomerisasie dramaties beïnvloed het, naamlik die kokatalisatorkonsentrasie en die reaksietemperatuur (Tr), is verder met die meer komplekse Zr-metalloseen- en tridentaat bis(imino)piridienyster(II)-katalisatorsisteme ondersoek. Uit die drie reekse katalisatore wat ondersoek is, is vier geïdentifiseer wat die hoogste aktiwiteit getoon het, en die potensiaal het om vir die dimerisasie van langerketting 1-alkene gebruik te kan word.

Oligomerisation of longer chain 1-alkenes in the presence of Cp2MCl2-, more complex Zrmetallocene and tridentate bis(imino)pyridine iron(II) catalyst systems

1-alkenes represent a large part of the commercial market and since oligomers thereof are important intermediates for specialty chemicals, they warrant further study. Metallocene catalysts are a promising development, since metallocenes, such as Cp2ZrCl2 (Cp = cyclopentadienyl), are easily obtainable. Examples of the oligomerisation of higher 1-alkenes are limited and there is a shortage of in-depth studies on these types of catalysts [3, 8–39]. It is also very apparent that only low MAO loadings lead to the formation of oligomers, and at higher loadings, polymerisation takes place [3, 18–29]. In an effort to increase the knowledge base of the oligomerisation of 1-alkenes a series of Cp2MCl2-catalysts (M = Zr (1), Ti (2), Hf (3) and Nb(4)), more complex Zr-metallocene (5 to 7) and tridentate bis(imino)pyridine iron(II) (8 to 11) catalyst systems was investigated (Figure 4). The specific aim was to determine the oligomerisation activity and selectivity of these catalysts in the presence of MAO as co-catalyst. Several factors can influence the catalyst activity during the conversion of 1-alkenes, namely activation temperature (Ta), activation time (ta), reaction temperature (Tr), co-catalyst concentration, the transition metal (M), and the monomer (mo) concentration. All these factors were investigated for the metallocene catalysts (1 to 4). The choice of ligand and bridging compound of the metallocene catalysts influenced the properties of the polymers obtained during reactions. The three more complex metallocene catalysts, 5 to 7, were investigated for their ability to oligomerise higher 1-alkenes. An important development in 1-alkene polymerisation catalysts was the discovery of the Group 8 iron catalysts, the so-called neutral tridentate bis(imino)pyridine iron(II) catalysts. Four catalysts of this type, 8 to 11, were identified for investigation of their activity with regard to the oligomerisation of higher chain 1-alkenes. Many factors can influence the catalyst activity during the conversion of 1-alkenes; in this study, only the reaction temperature (Tr) and co-catalyst concentration were varied because they were found to be major factors in determining the catalytic activity. The activity of the catalysts and degree of oligomerisation (n) were investigated with regard to 1-heptene and 1-octene.

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2018-12-01
2019-06-17

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