Pekka Sormunen

Modification of olefin polymerization catalysts. III. A 13C CP-MAS NMR study of adsorption of silyl ethers on MgCl2-supported Ziegler-Natta catalysts

Abstract A 13 C CP-MAS NMR and elemental analysis study of adsorption and interaction of silyl ethers, RSi(OMe) 3 (R = Et, Ph, OMe), as internal and external electron donors with MgCl 2 -supported Ziegler-Natta catalyst has been carried out. A chemical activation of anhydrous MgCl 2 with EtOH and AlEt 2 3 produces a high-surface-area support stabilized by an organoaluminium compound, AlEt 2 (OEt). In a treatment of the aluminium-modified MgCl 2 support with silyl ether, the aluminium surface complex is retained and silyl ether is almost totally incorporated into the support. 13 C CP-MAS NMR data of the methoxy region indicate that a mobile liquid-like silyl ether species dominates, except in the case of Si(OMe) 4 , where a more strongly bound species is also present on the support. TiCl 4 treatment removes the weakly adsorbed silyl ether species, leaving a species which is attributed to an aluminium-bound silyl ether surface complex. No evidence of titanium-bound silyl ether species was found in the solid state or in solution where TiCl 4 undergoes with silyl ethers an exchange reaction forming a yellow solid identified as [TiCl 2 (OMe) 2 ] x . Activation of the catalyst with AlEt 3 at a high Al: Ti ratio produces a material with a low silyl ether coverage showing a weak methoxy signal in 13 C CP-MAS. The linewidths of the observed signals in 13 C CP-MAS NMR are in the range 5–10 ppm at every stage of preparation of the catalyst, indicating heterogeneity of the coordination sites on the surface of chemically activated MgCl 2 .

Modification of olefin polymerization catalysts. II: A 29Si NMR study on the complexation of silyl ethers with triethylaluminium

Abstract The effect of complexation with a Lewis acid, AlEt 3 , and alkylation on the chemical shift of silyl ethers has been studied using 29 Si NMR spectroscopy. The substitution of a methoxy group for an ethyl group shifts the 29 Si signal on an average by 36.9 ppm to lower field, and the signal for the complexed silyl ether is usually shifted to lower field compared with that for the uncomplexed ether, the shift varying between − 1.4 and 18.1 ppm. Dynamic processes have been observed for some of the spectra; this is interpreted in terms of competition of Al acceptors for the several silyl ethers simultaneous present.

Solution NMR and FT-IR studies on the reactions and the complexes of silyl ethers with triethylaluminium

Complexation and reactions of silyl ethers RnSi(OMe)4−n (n = 0−3, R = Ph, alkyl) with AlEt3 were studied in benzene and followed by 13C and 29Si NMR. In the presence of excess AlEt3, of five consecutive steps: alternating complexation and alkylation of silyl ethers, Ph(Et)nSi(OMe)3−n (n = 1.2), and dialkyl-aluminium alkoxodes, (Et2AlOMe3)n (n = 2.3).

The influence of crystal water on the performance of a Ziegler-Natta catalyst in propylene polymerization

Ziegler-Natta catalysts are the most common catalysts when producing polypropylene. The polymerization process is disturbed even by minute amounts of water. Great care is therefor taken to avoid moisture both when producing the catalyst and when performing the polymerization.

11. A 13C CP - MAS NMR and Elemental Analysis Study of Adsorption of Silyl Ethers on the MgCl2-Supported Ziegler-Natta Catalysts

We describe here our results from a 13 C CP-MAS NMR and elemental analysis study of adsorption and interaction of a silyl ether, RSi(OMe) 3 (R = Ph), as an internal and an external electron donor with a MgCl 2 -supported Ziegler-Natta catalyst. A chemical activation of anhydrous MgCl 2 with EtOH and AlEt 3 produces a high surface area support stabilized by an organoaluminium compound, AlEt 2 (OEt). In a treatment of the thus obtained MgCl 2 with silyl ether the aluminium surface complex is retained and silyl ether is almost totally incorporated into the support. The effects of TiCl 4 and AlEt 3 treatments are also discussed.