Dae Sik Hong

The effect of water and acidity of the clay for ethylene polymerization over Cp2ZrCl2 supported on TMA-modified clay materials

Abstract The organic aluminum compounds (OACs) have been prepared on the surface of clay such as montmorillonite K-10 (MMT-10) and Kunipia by reaction of partial hydrolysis of trimethylaluminum (TMA). The effect of the water and acidity of the clay in ethylene polymerization was investigated over Cp 2 ZrCl 2 supported on the TMA-modified clay. Irrespective of whether water was present or not in the clay, Cp 2 ZrCl 2 supported on the TMA-modified clay showed catalytic activity for ethylene polymerization when acidic MMT-10 was used. However, in the case of basic Kunipia, no catalytic activity for ethylene polymerization was obtained. When Kunipia was changed to acidic by intercalation of an inorganic compound, Cp 2 ZrCl 2 showed the catalytic activity for ethylene polymerization in combination with the products of the partial hydrolysis of TMA on acidified Kunipia without methylaluminoxane (MAO).

Olefin homopolymerization catalyzed over asymmetric and symmetric ni(II) diimine complexes

Symmetric and asymmetric Ni(II) diimine complexes such as 2-[(2,6-diisopropylphenylimino)methyl]pyridine nickel(II) dibromide (a), 2-[1-(2,6-diisopropylphenylimino)ethyl]pyridine nickel(II) dibromide (b) and [1,2-bis(2,6-diisopropylphenylimino)] acenaphthene nickel(II) dibromide (c) were synthesized. For olefin homopolymerization, asymmetric Ni(II) diimine complexes [(a) & (b)] were compared with symmetric system (c). Asymmetric Ni(II) diimine complexes exhibited less catalytic activity and thermal stability as well as more b-hydride elimination than a symmetric diimine complex (c). The activity of (a) was larger than that of (b), which indicates that methyl group has a contribution to the instability of catalyst by s bond vibration rather than the stabilization of the active site by electron releasing property.

Preparation of Novel Supported Metallocene and their Olefin Polymerization Capabilities

Cp2ZrCl2 confined inside the supercage of NaY zeolite (NaY/MAO/Cp2ZrCl2) provides shape-selective copolymerization in which comonomer reactivity ratio depends on the shape and size of comonomer. In ethylene/propylene copolymerization over NaY/MAO/Cp2ZrCl2, a comonomer enhancement effect on the polymerization rate was observed, whereas in ethylene/1-hexene copolymerization comonomer enhancement effect was not observed. Comonomer depression effect was observed in ethylene/1-octene copolymerization. In ethylene/isobutylene copolymerization, isobutylene did not influence the polymerization rate. Copolymerization rate was also the same as the ethylene homopolymerization rate, indicating that isobutylene could not diffuse into the pores of the NaY zeolite during copolymerization because the kinetic diameter of isobutylene is larger than the pore diameter of NaY preadsorbed with methyl-aluminoxane (MAO). The comonomer content in the copolymer chain prepared with NaY/MAO/Cp2ZrCl2 was less by about one-half than that in the copolymer chain prepared with Cp2ZrCl2. Melting endotherm measured with DSC after successive annealing of copolymer shows that copolymers prepared with NaY/MAO/Cp2ZrCl2 show a narrower comonomer distribution than that prepared with Cp2ZrCl2.

Ethylene polymerization catalyzed over single site Ni complex catalysts supported on silica

The characterization of ethylene polymerization behaviors catalyzed over supported-Ni catalysts activated by MAO was reported. Supported-Ni catalysts were prepared by treating silica with MAO or TIBAL, followed by reacting pretreated silica with [(2,6-diiPrPh)2DABAn]NiBr2(1), [(2-py-CH=N-2,6-di-iPrPh)NiBr2](2) and [(2-py-C(CH3)=N-2,6-diiPrPh) NiBr2](3). In ethylene polymerization with Silica/MAO/(1), Silica/TIBAL/(1), a maximum activity was obtained at 30°C in all cases. The maximum activity is about 1/4 of that of corresponding unsupported catalyst. As polymerization temperature increased, the number and kinds of branching increased, whereas the molecular weight of prepared polymers decreased because of enhanced β-hydride elimination and reinsertion process. In ethylene polymerization with Silica/MAO/(2) and Silica/MAO/(3), powders were produced between 0°C and 50°C. The catalytic activity of Silica/MAO/(2) was higher than that of Silica/MAO/(3) in ethylene polymerization.