Wolfgang Fenzl

Supported nickel catalysts for ethylene oligomerization

Abstract New supported nickel catalysts for ethylene oligomerization have been obtained by the reaction of the nickel complex (I) with functional groups of modified silica (or alumina) or with magnesium hydride. Silica and alumina were modified by treatment with Al(CH3)3 or with Ti(CH2C6H5)4. A number of the synthesized catalysts exhibit high activity and high selectivity in ethylene oligomerization. At high temperature (above 90 °C) some catalysts produced a mixture of linear α-olefins and polymer. Experimental data on the interaction of the Ni complex I with the different supports and the composition of the surface Ni complexes are reported.

Heterogenization of a homogeneous nickel chelate ethylene oligomerization catalyst

Abstract Novel supported nickel catalysts for ethylene oligomerization have been synthesized. Thus, silica or alumina has been modified using Ph 2 PCH 2 CH 2 Si(OEt) 3 . The resulting supported phosphine was reacted with equimolar amounts of bis(cyclooctadiene)nickel and triphenylphosphonium 2-oxo-2-phenylethylide, yielding: E = Si of silica or Al of alumina, n = 1, 2 In this way a well-known homogeneous catalyst has been fixed on a support chemically. Activity and selectivity of the new catalysts are similar to those of the corresponding homogeneous but the activity can be increased tenfold by treatment with hydrogen.

Ethylene Insertion with Soluble Ziegler Catalysts: Direct Insight into the Reaction Using Enriched 13C2 H4 and 13C NMR Spectroscopy II. The System Cp2TiMeCl/AlMeCl2/13C2H4

Abstract The elementary processes involved in the polymerization of ethylene by soluble Ziegler catalysts of the type Cp2TiMeCl/AlMeCl2 have been studied by 13C NMR spectroscopy. Using 13C-enriched ethylene, detailed information was obtained directly on the system in the course of the polymerization. No spectroscopic evidence was found for precoordination of the monomer. The development of the oligomer distribution, which could be followed spectroscopically, proves that the mechanism proposed by Olivé cannot be correct. These experiments show conclusively that the ethylene is inserted into the titanium-carbon bond.

19. Co- and Terpolymerization of Ethene and Higher α-Olefins with MgH2 Supported Ziegler Catalysts: New Mechanistic Insight via the True Reactivity Ratios

Publisher Summary The determination of the true reactivity ratios is possible, at the present, only by means of analysis of the polymer product formed via the different active centers. This can be achieved by the analysis of the 13 C NMR spectrum for the unequivocal copolymer signals assignments in the original polymer mixture, or for the isolated copolymer signals. The objective of this chapter is to demonstrate how this right way leads to the estimation of the true copolymerization parameters and how; as a consequence, new mechanistical details are obtained in ethene/higher α-olefin copolymerization reactions using super active MgH 2 /TiCl 4 /AlEt 3 Ziegler–catalyst system. For the estimation of the copolymerization parameters it is useful to discern between the overall or mixed parameters, and the true copolymerization parameters. First, it is assumed that there are only uniform active centers located on the catalyst surface, ethene and comonomer peaks in the 13 C NMR spectrum of the polymer mixture is used for the estimation of the copolymerization parameters according to the Mayo–Lewis equation. This evaluation, via the r 1 versus r 2 diagram, leads to the overall or mixed copolymerization parameters. The Mayo–Lewis equation describes the composition of the copolymer as a function of the initial monomers mixture and the copolymerization parameters.

Molecular Behaviour of Soluble Catalysts for Olefin Polymerization Part I: Ethylene insertion with soluble Ziegler Catalysts

The development of the oligomer distribution during the polymerization of 13 C enriched ethylene by soluble Ziegler catalyst systems of the type Cp 2 TiMeCl/AlMe n Cl n was followed by 13 C NMR spectroscopy. It is shown that the rate of formation of new chains can be monitored directly from the spectra. The concentrations of Ti-propyl and Ti-pentyl species during the polymerization were followed; both attain a steady state concentration. These results give a greater insight into the way that the oligomer distribution develops and into the dependence on the chain length of the first insertion steps.