Comparison of Support Effects on Phillips and Metallocene Catalysts

Abstract

Both metallocene and Phillips chromium catalysts are used in the commercial manufacture of polyethylene. Unlike most other commercial metallocene systems, the Chevron Phillips Chemical (CPC) platform does not use methylaluminoxane or fluoroorganic boranes. Instead, the support itself serves to activate (ionize) the metallocenes, which then polymerize ethylene at high activity. Most of these solid acid supports can also be used to anchor Cr to make a Phillips catalyst. This provides an interesting opportunity to compare the polymerization responses by these two disparate systems, Phillips Cr and CPC metallocene, when supported on the same solid acid carriers. In this study, both chromium oxide and several metallocenes were deposited onto a variety of solid oxides, under a variety of conditions, and the resulting support effects were observed and compared. Although using seemingly different chemistries, the two catalyst systems exhibited a surprising number of similarities, which can be attributed to the acidity and porosity of these diverse supports.

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

“…1 H NMR (C 6 D 6 ): δ 7.97 and 7.95 (d, J = 1.4 Hz, 1H), 7.87 (d, J = 8.3 Hz, 1H), 7.79 and 7.78 (s, 1H), 7.64 and 7.62 (s, 1H), 7.51 and 7.50 (dd, 3 J = 3.4 Hz, 4 J = 1.4 Hz, 1H), 7.44 and 7.42 (dd, 3 J = 8.7 Hz, 4 J = 1.4 Hz, 1H), 6.23 (q, 4 J = 1.4 Hz, 1H), 3.31 and 3.30 (q, J = 6.2 Hz, 2H), 2.13 (d, 4 J = 1.4 Hz, 3H, SCCH 3 ), 2.03 (s, 3H, CH 3 ), 1.93 and 1.89 (s, 3H, CH 3 ), 1.39, 1.36, 1.34, and 1.32 (s, 18H, tBu), 1.26 and 1.08 (s, 3H, Si-CH 3 ), 1. 15…”

“…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].…”

Mechanistic Insights of Ethylene Polymerization on Phillips Chromium Catalysts

“…Chemical modification of the silica surface provides significant benefits over the use of inorganic phases different from silica. In particular, TiO 2 - and Al 2 O 3 -containing silica-based PCCs are long-lasting and have been successfully commercialized [ 8 , 15 , 16 ]. In further studies, fluorination of the silica supports at the stage of thermal treatment proved to be quite effective in terms of catalytic activity and PE characteristics [ 3 ]; the impact of fluorination of silica on the properties of PCCs was studied recently by Liu et al [ 17 , 18 ] (see Section 6.5 ).…”

“…On the other hand, a larger pore volume and pore diameter are required for the disintegration of the catalyst particles during polymerization. This ensures high and consistent activity as well as excellent morphology of the PE [ 16 ]. However, the pronounced dependence of the PE characteristics from support properties allowed the development of a simple and efficient method of the modification of PCCs based on the treatment of commercial mesoporous silica by Si(OEt) 4 oligomers and the Cr source before oxidative calcination [ 31 ].…”

Novel Imido‐Cr/Silica Ethylene Polymerization Catalysts Modified from the Phillips Catalyst

“…[1] The vigor and vitality of this catalyst is maintained by its continuous and numerous recipe upgrades, which are generally promoted by several fundamental methods including calcination treatment, activation manipulation, as well as physical and chemical modification. [2][3][4][5] Regarding to chemical modification, it is the inorganic components, such as metal oxides, mineral acid, halogen compounds, and the combination of them, that are commonly employed, while polar organic modifiers are scarcely investigated. It probably results from the highly unsaturated and electronically deficient nature of the Cr center, which is likely to be poisoned by these polar organic components, leading to lower activities.…”