Correlating the Morphological Evolution of Individual Catalyst Particles to the Kinetic Behavior of Metallocene-Based Ethylene Polymerization Catalysts

Abstract

Kinetics-based differences in the early stage fragmentation of two structurally analogous silica-supported hafnocene- and zirconocene-based catalysts were observed during gas-phase ethylene polymerization at low pressures. A combination of focused ion beam-scanning electron microscopy (FIB-SEM) and nanoscale infrared photoinduced force microscopy (IR PiFM) revealed notable differences in the distribution of the support, polymer, and composite phases between the two catalyst materials. By means of time-resolved probe molecule infrared spectroscopy, correlations between this divergence in morphology and the kinetic behavior of the catalysts’ active sites were established. The rate of polymer formation, a property that is inherently related to a catalyst’s kinetics and the applied reaction conditions, ultimately governs mass transfer and thus the degree of homogeneity achieved during support fragmentation. In the absence of strong mass transfer limitations, a layer-by-layer mechanism dominates at the level of the individual catalyst support domains under the given experimental conditions.

Syntheses of Silylene-Bridged Thiophene-Fused Cyclopentadienyl ansa-Metallocene Complexes for Preparing High-Performance Supported Catalyst

“…Silica (SYLOPOL-2410) was obtained from GRACE and used as received (Yeosu, South Korea). The 1 H NMR (600 MHz) and 13 C NMR (150 MHz) spectra were recorded on a JEOL (Tokyo, Japan) ECZ 600 instrument. Gel permeation chromatography (GPC) was performed in 1,2,4-trichlorobenzene at 160 • C using an Agilent PL-GPC 220 system equipped with an RI detector and two columns (PLgel mixed-B 7.5 × 300 mm from Varian (Polymer Lab (Salop, UK)).…”

“…1 H NMR (C 6 D 6 ): δ 7.79 (d, J = 7.6 Hz, 1H), 7.76 (d, J = 7.6 Hz, 2H), 7.33 (d, J = 7.6 Hz, 1H), 7.29 (t, J = 7.6 Hz, 1H), 7.26 (t, J = 7.6 Hz, 1H), 7.23 (td, 3 J = 7.6 Hz, 4 J = 1.4 Hz, 1H), 7.13 (td, 3 J = 7.6 Hz, 4 J = 1.4 Hz, 1H), 4.47 (s, 1H), 3.55 (s, 1H), 2.22 (s, 3H, CH 3 ), 2.14 (s, 3H, CH 3 ), 2.07 (s, 3H, CH 3 ), 1.74 (s, 3H, CH 3 ), −0.23 (s, 3H, SiCH 3 ), and −0.44 (s, 3H, SiCH 3 ) ppm. 13 C{ 1 H} NMR (C 6 D 6 ): δ 151. 0, 145.6, 145.6, 141.4, 138.1, 136.0, 133.7, 131.0, 126.7, 126.5, 126.0, 125.8, 125.6, 124.7, 124.6, 120.5, 120.3, 45.6, 40.8, 14.7, 13.7, 12.4, 12.2, −6.5, and −6.9 ppm.…”

“…(s, 1H), 1.92 (s, 3H, CH 3 ), 1.68 (s, 3H, CH 3 ), and −0.39 (s, 3H, SiCH 3 ), −0.56 (s, 3H, SiCH 3 ) ppm. 13…”

“…1 H NMR (C 6 D 6 ): δ 8.02 (s, 1H), 7.83 (d, J = 8.3 Hz, 1H), 7.80 (d, J = 8.3 Hz, 1H), 7.54 (s, 1H), 7.43 (dd, 3 J = 8.3 Hz, 4 J = 1.4 Hz, 1H), 7.34 (dd, 3 J = 8.3 Hz, 4 J = 1.4 Hz, 1H), 6.64 (q, J = 1.2 Hz, 1H), 4.47 (s, 1H), 3.74 (s, 1H), 2.35 (s, 3H, CH 3 ), 2.02 (s, 3H, CH 3 ), 1.86 (s, 3H, CH 3 ), 1.39 (s, 9H, tBu), 1.32 (s, 9H, tBu), −0.15 (s, 3H, SiCH 3 ), and −0.40 (s, 3H, SiCH 3 ) ppm. 13 34.9, 31.9, 31.9, 16.1, 15.1, 11.9, −6.3, and −6.9 ppm. HRMS(EI): m/z calcd.…”

“…When a homogeneous catalyst is injected, as dissolved, into a slurry-or gas-phase reactor, the shape and size of the generated polymer particles are irregularly uncontrolled, making stable operation impossible (termed 'fouling') as well as causing low productivity due to low bulk density. Because a large portion of PE and PP is produced by the slurry and gas-phase processes, high-performance supported catalysts are essential in the industrial sector [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”