Gas‐phase olefin polymerization over supported metallocene/MAO catalysts: influence of support on activity and polydispersity

Abstract

Three catalysts obtained by supporting bis(n‐butylcyclopentadienyl)zirconium dichloride/methylaluminoxane on: (1) porous crosslinked poly(2‐hydroxyethylmethacrylate‐co‐styrene‐co‐divinylbenzene) particles (CAT1); (2) swellable crosslinked poly(styrene‐co‐divinylbenzene) particles (CAT2); and (3) by evaporating the catalyst precursors solution to dry powder, CAT3 were used in gas‐phase polymerization of ethylene, and ethylene/1‐hexene in a 2 L semi‐batch reactor at 80 °C and 1.4 MPa. The average polymerization activities of the three catalysts were 12.3–15.5, 4.2–10.1, and 14.3–62.9 ton PE (mol Zr h)−1 respectively. CAT1 and CAT3 produced polyethylenes with a polydispersity range of 2.3–2.7, while that of CAT2 was 3.5–6.4. The supported catalysts produced polyolefin particles with bulk density of 0.36–0.43 g ml−1, and essentially no fines. Ethylene/1‐hexene co‐polymerization (7 mol m−3 initial 1‐hexene concentration in the reactor) increased polymerization activities and produced lower‐molar‐mass co‐polymers. At 21 mol m−3 1‐hexene the polymerization activities decreased, but the relative amount of the low‐molar‐mass co‐polymer for CAT2 increased, leading to higher polydispersity. Copyright © 2006 Society of Chemical Industry

Condensed Mode Cooling for Ethylene Polymerization: Part II. The Effect of Different Condensable Comonomers and Hydrogen on Polymerization Rate

“…In their study of gas phase ethylene copolymerizations, also using supported Cp 2 ZrCl 2 /MAO catalysts, Hammawa and Wanke again found that the comonomer effect was more pronounced for shorter alkenes than for longer ones. However, they also demonstrated that the friability of the support was related to the importance of the comonomer effect, with more compact, less friable particles having a much higher alkene response.…”

Effects of propylene prepolymerization on ethylene/1‐hexene and ethylene/1‐octene copolymerization with an immobilized metallocene catalyst

“…However, compositional heterogeneity in the resulting copolymer may still occur, even in the case of a single-center catalyst. [13][14][15][16] Fink et al 14 ascribed the compositional distribution of ethylene/1-hexene copolymers prepared with a SiO 2 /methylaluminoxane (MAO)/zirconocene system to the formation, during the initial stages of polymerization, of a copolymer envelope around the catalyst particle. Easier diffusion of the smaller monomer, ethylene, with respect to 1-hexene was proposed to lead to a polymer particle comprising an ethylene-rich center surrounded by an outer layer of the copolymer, thus giving a broad overall chemical composition distribution (CCD).…”

The role of polymerizable organophilic clay during preparing polyethylene nanocomposite via filling polymerization

“…The same phenomenon was also reported in other researches where copolymerizable monomers took part in polymerization. 49,50 In contrast, the M w of PE in PE/12MMTs composite (12PE1) is close to that of the neat PE. For P-PE5, homopolymerized PE and copolymerized PE were separated by extraction using decalin as solvent in a Soxhlet extractor for 48 h, and then the MMTs in the residue were removed by reacting with hydrogen fluoride (HF) before examination.…”