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Polymerization of ethylene in the presence of hydrogen over supported vanadium-magnesium catalysts

Mikenas T. B., Zakharov V. A., Echevskaya L. G., Matsko M. A.

Polimery

2000

T. 45, nr 5

349-352

Catalyst activity was studied in a slurry polymerization of ethylene carried out over supported VCl4/MgCl2 and VOCl3/MgCl2 cata-lysts in relation to hydrogen concentration (0–40 mmols/L, i.e., 0–2 bar) and to Al(i-Bu)3 and Al(i-Bu)2H, each used as cocatalyst. Hydrogen was found to reduce the activity of the catalyst by 2 to 6 times. The deactivation occurring in the presence of hydrogen was directly related to hydrogen pressure and found to be due to the hydride species of organoaluminum com-pounds forming in the side reaction of AlR3 with the V-H bonds accompanied by adsorption of alkylaluminum hydride on active sites. A sequence of reactions is suggested (eqns. 2-5) to explain the deactivation and reactivation of the catalyst.