Novel binary chlorides containing TiCl₃ as components of coordination catalysts for ethylene polymerization. II. Behavior of the resulting catalyst systems

Abstract

Synopsis /Binary chlorides described in part I yielded very active catalyst systems for HDPE synthesis when they were associated with (i-C4H&Al. Very high initial polymerization rates were observed for systems bases on MnC12-TiC13, MnC1~2TiC13, or FeC12~2TiC13 (III), but high yields, i.e., above 30 kg polymer/g Ti, could be reached only using moderate pressure of ethylene. Hydrogen consumption during ethylene polymerization was observed in the case of catalysts based on AlC1~3TiC13, CrC13-3TiC13, and other binary chlorides containing elements of the VIII group. Relevant amounts of ethane were found in the case of systems 111, V, and VIII. All the mixed chlorides studied were able to reduce cyclohexene in the presence of H2 and (i-CdH&Al, even though with different kinetic courses. Compounds 11,111, V, and VIII and (MgC12)1,yTiC13 and AlCl~3TiC13 were very active. The results have been explained on the basis of soluhilization processes involving the heterogeneous catalysts which actually were experimentally verified during cyclohexene reduction. Analogous processes may occur also during HDPE synthesis. INTRODUCTIONIn part I,' new binary chlorides CrC13-3(TiC13) (I), MoC1r3TiC13 (II), FeClY 2TiC13 (III), MnC1~2TiC13 (IV), NiC1~2TiC13 (V), and MnCl2.TiCl3 (VI) containing usually the y-modification of TiC13 were described. Their ability to give catalyst systems for the low-pressure polymerization of ethylene when associated to A1R3 was also mentioned.In this paper, the dependence of the polymerization rate on time and the influence of hydrogen used as regulator of the polymer molecular weight on some side processes, i.e., monomer hydrogenation and catalyst solubilization, are presented. Relevant differences have been encountered among the systems based on different binary halides and depending on the element associated with Tic13 in the solid solution. RESULTS AND DISCUSSION Ethylene PolymerizationProducts 1 through VI, and also VTil.lC16.~ (VII) and CoTil.6C16.6 (VIII), have been associated with Al(i-C4H9)3 to investigate their catalytic activity toward low-pressure ethylene polymerization. By working in the presence of HZ as Journal of Applied Polymer Science, Vol. 23,1333-1344(1979 Table I were obtained. They are referred to the catalytic activity shown by AlC13-3TiC13, while the possible contribution to the catalyst efficiency of the binary chloride due to the second transition metal has been neglected only in a first approximation. In fact, this assumption is not rigorous.2 However, Table I shows that catalyst systems based on 111, IV, and VI are about three times more efficient than the system based on AlC13-3TiC13. The hydrogen sensitivity, i.e., the dependence of the polymer molecular weight on the Hz concentration, can be considered satisfactory in the case of VI, whereas it is rather poor in the case of I11 and I.In part I, mention has been made of the difficulty to relate the overall catalyst efficiency to the surface area ( S A ) value of the binary chlorides used. Analogous difficulties in correlating th...

Ziegler–Natta Catalysis

“…In ethylene polymerizations at 5 atm pressure of monomer, good yields (1-28 kg polymer per g Ti) were achieved using triisobutylaluminium as cocatalyst. 98 Activity of the catalyst, however, decayed rapidly during the polymerization, so that overall yields were not as high as with some other systems. …”

Stereochemistry of Polymerization

“…Gallium is also active but expensive. Zinc and magnesium alkyls are the most thoroughly studied group II metal component [Greco et al, 1979]; beryllium compounds have received little attention because of their toxicity. Lithium, sodium, and potassium alkyls are the most studied group I metal component.…”