Details

Autor(en) / Beteiligte

• Gil, Marcelo P.
• dos Santos, João H.Z.
• Casagrande, Osvaldo L.

Titel

Polymerization of ethylene by the tris(pyrazolyl)borate titanium(IV) compound immobilized on MAO-modified silicas

Ist Teil von

• Journal of molecular catalysis. A, Chemical, 2004-02, Vol.209 (1), p.163-169

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2004

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• The immobilization of soluble catalyst { Tp Ms ∗ }TiCl 3 on silica and MAO-modified silicas containing 4.0, 8.0 and 23.0 wt.% Al/SiO 2 and their use in ethylene polymerization are described. The immobilization of soluble catalyst { Tp Ms ∗ }TiCl 3 ( Tp Ms ∗ HB(3-mesityl-pyrazolyl) 2(5-mesityl-pyrazolyl) −) on silica and MAO-modified silicas containing 4.0, 8.0 and 23.0 wt.% Al/SiO 2 yields active supported catalysts for ethylene polymerization. Among the supported catalysts studied by XRF spectroscopy, higher titanium content was obtained using MAO-modified silica containing 8.0 wt.% Al/SiO 2 as support. For the ethylene polymerization reactions carried out in hexane at 60 °C using a combination of triisobutylaluminum (TiBA) and methylaluminoxane (MAO) (1:1), the activities varied between 24.4 and 113.5 kg of PE/mol [Ti] h. The highest activity is reached using MAO-modified silica containing 4.0 wt.% Al/SiO 2 as support. The viscosity-average molecular weights ( M ̄ v ) of the PE’s produced with the supported catalysts varying from 1.44 to 9.94×10 5 g/mol with melting temperatures in the range of 125–140 °C. The use of other Lewis acid cocatalysts, including TiBA, diethylaluminum chloride (DEAC), and trimethylaluminum (TMA) resulted also in the formation of active catalysts for ethylene polymerization. However, the activities are lower than that one using a combination of TiBA and MAO. The viscosity-average molecular weights ( M ̄ v ) of PE’s are influenced by varying the cocatalysts as well as the Al/Ti molar ratio. The supported catalyst generated in situ under ethylene atmosphere is roughly four times more active than supported one containing 4.0 wt.% Al/SiO 2.