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

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

Polimery 2000, No 5, 349


DOI: dx.doi.org/10.14314/polimery.2000.349


Summary

Catalyst activity was studied in a slurry polymerization of ethylene carried out over supported VCl4/MgCl2 and VOCl3/MgCl2 catalysts 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 compounds 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.
Keywords: polymerization of ethylene over vanadium-magnesium catalysts, deactivation of catalyst in the presence of hydrogen, Al(i-Bu)3 and Al(i-Bu)2H as cocatalysts, organoaluminum hydrides as deactivators
T. B. Mikenas, V. A. Zakharov, L. G. Echevskaya, M. A. Matsko (312 KB)
Polymerization of ethylene in the presence of hydrogen over supported vanadium-magnesium catalysts