III International Conference

STUDY OF METALLOCENE CATALYTIC SYSTEM Cp 4 Zr-MAOIN THE ABSENCE OF MONOMERPP-I-43Sedov I.V., Knerelman E.I., Russiyan L.N., Matkovskiy P.E., Aldoshin S.M.Institute of Problems of Chemical Physics RAN, Chernogolovka, Moscow region, RussiaE-mail: isedov01@rambler.ruSpectroscopic investigation of metallocene catalytic system Cp 4 Zr-MAO in the absenceof monomer was carried out. Obtained results can be used for detail description ofpolymerization mechanism.Tetrakiscyclopentadienyl zirconium (C 5 H 5 ) 4 Zr is one of the simplest cyclopentadienylzirconium derivatives. According to X-ray analysis, there are three η 5 -bonded C 5 H 5 -groupsand one η 1 -bonded C 5 H 5 -group in (C 5 H 5 ) 4 Zr molecule [1, 2]. In this respect, it is interesting tostudy catalytic properties of such compound in the polymerization process. In combinationwith МАО and/or other cocatalysts, (C 5 H 5 ) 4 Zr may be used as a soluble catalyst of homo- andcopolymerization of ethylene, and as a base for new supported catalysts creation. Ourpreliminary experiments showed that the productivity of soluble catalytic system (C 5 H 5 ) 4 Zr –MAO (I) during the process of ethylene polymerization (T = 60 o C , P = 5 bar, [(C 5 H 5 ) 4 Zr] =0.002 mmol/l, Al/Zr = 25000, 60 min) has achieved 742 kg PE/g Zr per hour. Later, it wasshown [3, 4] that the productivity could be increased to 2180 kg PE/g Zr. Thus, the purpose ofour work is to study the mechanism of component interaction in the described catalyticsystem (C 5 H 5 ) 4 Zr – MAO in the absence of monomer.The following results were obtained during analysis of UV-Vis spectra evolution.It was observed the fast accumulation of a product (I) (with absorbance max λ = 326 nm)in the first moment of the catalyst components mixing. The bathochromic shift may beexplained by formation of polarized metal – carbon bond containing an intermediate [5].Later, it was observed the product (I) consumption and a product (II) (absorbance max λ =372 nm) accumulation. By our suggestion, the second bathochromic shift is associated withthe further polarization of metal – carbon bond in nascent active species and the formation ofcontact ionic pair. The analysis of the kinetic regularities unambiguously established that theprocesses (I) and (II) were consecutive. After a lapse of time the product (II) concentrationdecreased. Obviously, it is explained by the active species collapse. Above process isaccompanied by a product (III) formation. The concentration of zirconocene and the Al/Zrmolar ratio do not influence on the products (I) and (II) formation. However, the increase of85