Influence of supports on gas-phase olefin polymerization over polymer-supported (n-BuCp)2-zirconium chloride/MAO catalysts

The influence of support properties on gas-phase olefin polymerization over polymer-supported (n-BuCp)2ZrCl2/MAO catalysts were investigated in a newly fabricated polymerization reactor with enhanced cooling. Inserting Kenics type static mixers into channels used for coolant flow enhanced the cooling efficiency of the new reactor; the coolant channels are drilled along the reactor wall. Good gas-phase temperature control was achieved in polymerization runs with maximum instantaneous rates up to 100 g-PE per hour. Polymerizations were typically run for 1 h at 80°C, 1.4 MPa and, for some runs, gas samples from the reactor were analyzed at 3 min intervals.;The polymerization rate profiles are typically acceleration-decay type. Residual aluminum alkyls in the reactor suppressed the initial polymerization rates, but average activities often increased due to broadening of the activity profiles. This effect increased with the amount of aluminum alkyl and decreasing alkyl size as follows: TEA > TIBA > TNOA.;Polymer-supported catalysts were prepared by sequentially contacting thermally treated supports with MAO and metallocene solutions followed by vacuum drying the suspensions. Low fragility supports resulted in catalysts that homopolymerized ethylene with low activity due to poor catalyst fragmentation. The product particles consisted of unfragmented catalyst core surrounded by loose polyethylene layer. The average ethylene homopolymerization activity of these catalysts 10--50 g PE/(g cat·h) increased 5--20 times when about 15 mol/m3 1-hexene was initially present in the gas-phase; the catalysts were completely fragmented during the copolymerization. Catalysts made with highly friable supports showed high activity during both ethylene, and ethylene/alpha-olefin polymerizations. 1-Hexene had less significant influence on activity than with the low friability supports under similar polymerization conditions.;The presence of 7.5 mol/m3 1-hexene resulted in copolymers of much lower molar masses than the homopolymers but further increases in the amount of 1-hexene did not result in significant additional molar mass decreases. Addition of about 10 ppm hydrogen in the reactor depressed the polymerization activity reversibly and lowered polymer molar mass. Polyethylene molar masses increased with ethylene pressure, and decreased with increasing catalyst particle size and polymerization temperature. The spherical morphology of the support particles was generally well replicated in the polymer particles.