Polymerization of ethylene with Cr[OC(CH₃)₃]₄/Al(C₂H₅)₂Cl as catalyst modified with some metal chlorides

Abstract

Polymerization of ethylene was carried out in toluene using the homogeneous catalytic system Cr[OC(CH3 h ]4 /Al(GH, hC1, combined with various metal chlorides (MtCS,). The polymerization activity was found to be strongly dependent upon the MtCL, used. A clear correlation was found between the activity and the elctronegativity X(MtX+ ) of the metal ion in MtCS, . MtCS, containing metal ions with X(MtX+ ) < 8,5 (electronegativity of the active C?+ ) show a markedly increased activity, whereas those with X(MtX+ ) > 8,5 have a rather decreased activity. Thus, for example, the catalyst combined with MgCb shows very high activity to give a linear polyethylene with a remarkably high molecular weight and narrow molecular weight distribution. A plausible mechanism for the enhancement of the activity by suitable MtCJ is proposed on the basis of these results.

Syntheses of chromium(III) complexes with Schiff-base ligands and their catalytic behaviors for ethylene polymerization

“…A large fraction of the catalysts, especially the industrially relevant ones, are heterogeneous systems prepared by the deposition of soluble Ti-, Zr-or Crcontaining precursors on high surface area supports, such as silica, alumina or magnesium chloride. Among these transition metals that catalyze the polymerization of olefins, chromium occupies a prominent position [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

Ethylene and propylene polymerizations with the MgCl2-supported tris(acetylacetonato)chromium-diethylaluminium chloride catalyst system

“…[3,4] The chromium catalysts obtained by reacting chromium(III) acetate monohydrate (Cr(CH 3 COO) 3 N H 2 O) with acetic acid and acetic anhydride also showed extremely high activity for ethylene homopolymerization with diethylaluminium chloride (DEAC) as cocatalyst. [5][6][7] The polymerization activity of this catalyst was significantly improved by the use of a suitable metal chloride, such as magnesium dichloride (MgCl 2 ) [8,9] as catalyst support. The MgCl 2 -supported chromium(III) stearate (Cr(C 17 H 35 COO) 3 )-DEAC catalyst system produced poly(propylene) with ca.…”