Olefin oligomerization
Tanja H. Ritter; Helmut G. Alt
Abstract
Nine different bis(arylimino)pyridine complexes of Fe(III) with different halide substituents (F, Cl, Br, I) at different positions of the iminophenyl group of the ligand have been synthesized, characterized and applied for homogeneous 1-pentene and 1-hexene oligomerization and co-oligomerization reactions ...
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Nine different bis(arylimino)pyridine complexes of Fe(III) with different halide substituents (F, Cl, Br, I) at different positions of the iminophenyl group of the ligand have been synthesized, characterized and applied for homogeneous 1-pentene and 1-hexene oligomerization and co-oligomerization reactions after activation with methylaluminoxane (MAO). The best activity in 1-hexene oligomerization (152 kg/mol.h) was observed for 4/ MAO with an iodine substituent in para position of the iminophenyl group. Fluorine substituents in the meta position of the iminophenyl group proved as disadvantageous (1 kg/mol.h) in homo-oligomerization reactions but advantageous in co-oligomerization reactions of 1-pentene and 1-hexene. Obviously, tiny electronic or steric differences at the active sites of the corresponding catalysts are responsible for this result (structure-property relationship). The product distributions of the co-dimerization reactions of 1-pentene and 1-hexene reflected a binominal behaviour with dominating co-products. The ratio of dimers is 1:2:1 (C10:C11:C12) while the trimers (pentadecenes up to octadecenes) show proportions of 1:3:3:1.
Olefin oligomerization
Tanja H. Ritter; Helmut G. Alt
Abstract
1-Pentene, respectively 1-hexene, were reacted with 13 homogeneous metallocene catalysts to give linear oligomerization products, predominantly dimers, with selectivities above 90%. The product distributions of the codimerization reactions of 1-pentene with 1-hexene reflected a binomial behaviour. Therefore, ...
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1-Pentene, respectively 1-hexene, were reacted with 13 homogeneous metallocene catalysts to give linear oligomerization products, predominantly dimers, with selectivities above 90%. The product distributions of the codimerization reactions of 1-pentene with 1-hexene reflected a binomial behaviour. Therefore, the ratio for dimers is 1:2:1 (C10:C11:C12) while the trimers (pentadecenes up to octadecenes) show a proportion of 1:3:3:1. By changing the ratio of the 1-pentene/1-hexene mixture, the binomial distribution switched to the side of products of the higher concentrated monomer. Even when using methyl branched olefins, the binomial product distribution could be observed. Alkenes with an internal double bond could not be dimerized under these conditions. The reactions with olefins containing a methyl group in β-position, a tert-butyl group or a neopentyl group failed. Addition of appropriate additives like tributylphosphine or aluminum powder raised both the activities and the selectivities for dimers, which means that the fraction of undecenes obtained from the codimerization reactions of 1-pentene and 1-hexene increased.
Catalysis
Andrea M. Rimkus; Helmut G. Alt
Abstract
Eight different zirconium phenoxyimine complexes were synthesized, characterized and tested as catalysts for ethylene polymerization. The phenoxyimine compounds were prepared by condensation of substituted salicylaldehydes with aliphatic and aromatic amines, the substituted salicylaldehydes from ortho ...
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Eight different zirconium phenoxyimine complexes were synthesized, characterized and tested as catalysts for ethylene polymerization. The phenoxyimine compounds were prepared by condensation of substituted salicylaldehydes with aliphatic and aromatic amines, the substituted salicylaldehydes from ortho substituted phenols and paraformaldehyde. The introduction of iodo substituents was achieved either by iodination of the aldehyde component followed by condensation with amines or the iodination of the aldehyde after the condensation with amines or the iodination via condensation with iodo substituted amines. Deprotonation of the hydroxy function of phenoxyimine compounds and reaction with zirconium tetrachloride gave mononuclear bis(phenoxyimine) zirconium complexes in good yields. These complexes were activated with methylaluminoxane (MAO) and applied for ethylene polymerization. The performances of the various catalysts were compared and structure-property-relationships were discussed.
Catalysis
Helmut G. Alt
Abstract
EEthylene polymerization catalysts became available in an enormous variety. The challenge in this research is to find catalysts that are able to connect ethylene molecules in such a way that not only linear chains are produced but variations like branched materials that possess very interesting mechanical ...
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EEthylene polymerization catalysts became available in an enormous variety. The challenge in this research is to find catalysts that are able to connect ethylene molecules in such a way that not only linear chains are produced but variations like branched materials that possess very interesting mechanical properties like linear low density polyethylene (LLDPE). In this contribution, three different types of catalysts are presented that are able to do not only one job at a time but three. These are “intelligent catalysts”. Catalysts of type 1 are homogeneous metallocene complexes that can be activated with methylaluminoxane (MAO).With ethylene they produce their own support and they become heterogeneous catalysts (self-immobilization) and they prevent fouling in polymerization reactors. The produced resin has evenly distributed ethyl branches (without a comonomer) with unique properties and the MAO that is necessary in the activation step can be recycled. Catalysts of type 2 are dinuclear complexes with two different active sites. One centre can oligomerize ethylene and the other one can copolymerize the in statu nascendi produced oligomers with ethylene to give branched LLDPE (a molecule as the smallest reactor for LLDPE) and/or bimodal resins.Catalysts of type 3 are MAO activated iron di (imino) pyridine complexes that are able to oligomerize ethylene to give not only oligomers with even numbered carbon atoms but also odd numbered ones. In this reaction, one catalyst does three jobs at a time: oligomerization, isomerization and metathesis of ethylene.
Catalysis
Haif Alshammari; Helmut G. Alt
Abstract
A series of dissymmetric dinuclear complexes were synthesized, as dual site catalysts in ethylene polymerization, by coupling the allylated a-diimine complexes of the metals Ti, Zr, V, Ni and Pd with the ansa-zirconocene complex [C5H4-SiH(Me)-C5H4]ZrCl2 possessing a hydride silane moiety. The different ...
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A series of dissymmetric dinuclear complexes were synthesized, as dual site catalysts in ethylene polymerization, by coupling the allylated a-diimine complexes of the metals Ti, Zr, V, Ni and Pd with the ansa-zirconocene complex [C5H4-SiH(Me)-C5H4]ZrCl2 possessing a hydride silane moiety. The different stages of syntheses included the formation of bis(cyclopentadienide)methyl silane which was utilized to prepare the silyl-bridged zirconocene complexes. The dinuclear complexes were prepared by mixing the latter complexes with allylated alpha-diimine via a hydrosilylation reaction using the Karstedt catalyst, platinum (0)1,3 divinyl-1,1,3,3,-tetramethyldisiloxane to react at room temperature for 40 h. These dinuclear complexes were activated with methylaluminoxane (MAO) and tested for the polymerization of ethylene. The dinuclear catalysts showed various activities depending on the nature of the metals and produced polyethylenes with broad or bimodal molecular weight distributions. The trend in polymerization activities was: Ni>Pd>V>Zr>Ti. The ethylene polymerization activities of the dinuclear catalysts were almost double the activities of their analogous alpha-diimine precursors.
