Phillips Cr/Silica Catalyst for Ethylene Polymerization

Polyethylene with Reverse Co‐monomer Incorporation: From an Industrial Serendipitous Discovery to Fundamental Understanding

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At riethylaluminium(TEAl)-modified Phillips ethylene polymerisation Cr/Ti/SiO 2 catalyst has been developed with two distinct active regions positioned respectively in the inner core and outer shell of the catalyst particle.D RIFTS, EPR, UV-Vis-NIR DRS,S TXM, SEM-EDX and GPC-IR studies revealed that the catalyst produces simultaneously two different polymers,i .e., low molecular weight linear-chain polyethylene in the Ti-abundant catalyst particle shell and high molecular weight short-chain branched polyethylene in the Tiscarce catalyst particle core.Co-monomers for the short-chain branched polymer were generated in situ within the TEAlimpregnated confined space of the Ti-scarce catalyst particle core in close proximity to the active sites that produced the high molecular weight polymer.T hese results demonstrate that the catalyst particle architecture directly affects polymer composition, offering the perspective of making high-performance polyethylene from as ingle reactor system using this modified Phillips catalyst.Several years ago at an industrial ethylene polymerisation plant, the in situ generation of co-monomer on aC rp olymerization line using the well-known Cr/Ti/SiO 2 Phillips-type catalyst was reported. [1][2][3][4][5][6][7][8] Hence,t he co-feeding of 1-hexene was significantly reduced in order to keep ap olymer with similar content of co-monomer.T he interesting finding was that 1-hexene was the major component, while butene and other oligomers were present in lower concentration. Moreover, the properties of the polyethylene produced were not affected despite the presence of butene.Onthe contrary,the polymer made even exhibited some improvements.T he hypothetical explanation for in situ co-monomer generation was ac ontamination of the recycling feeds by triethylaluminium (TEAl), as there were several lines with ac ommon recycling section.

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Novel SiO2‐Supported Chromium Oxide(Cr)/Vanadium Oxide(V) Bimetallic Catalysts for Production of Bimodal Polyethylene

“…[15][16][17][18] Following this trend, a third-generation Phillips catalyst has also been developed to produce the bimodal MWD polyethylene. [4] The catalyst of Cp 2 ZrCl 2 or (n-BuCp) 2 HfCl 2 metallocene and chromium oxide co-supported on montmorillonite, [19] or the chromium oxide and (n-BuCp) 2 ZrCl 2 co-supported onto several inorganic carriers, [20] was reported in the literature. Due to the strong H 2 response of metallocene active site in ethylene polymerization process, Paredes et al [21] also found the catalyst with CrO x /(n-BuCp) 2 ZrCl 2 co-supported on Al-SBA-15 led to the PE with wide bimodal MWD.…”

“…[24][25][26][27][28] The vanadiumbased catalysts for homopolymerization of ethylene and/or copolymerization of ethylene with a-olefin are usually MgCl 2 -supported catalysts, known as vanadium-magnesium catalysts. [29][30][31] As one of the traditional Z-N catalysts, vanadium species in the form of halides, such as VOCl 3 and VCl 4 , are irreplaceable and widely used in the industrial synthesis of ethylene-propylene-diene elastomers and ethylene propylene rubber. Meanwhile, it was found that the vanadium catalyst was featured with excellent capability to get polyethylene with narrow MWD, high incorporation of 1-alkenes in ethylene/1-alkene copolymerization reactions, and homogeneous SCBD along the copolymer chains.…”

“…[1][2][3][4] This well-known catalyst, as highly dispersed chromium oxide covalently anchored on silica gel surface, was first discovered by Hogan and Banks in Phillips Petroleum Company in early 1950s. [5,6] Compared with the other polyolefin catalysts, such as Ziegler-Natta titanium chloride catalysts and metallocene catalysts, the polyethylene produced by Phillips catalyst using single reactor process was characterized with very broad molecular weight distribution (MWD, usually between 10 and 30) reflecting the numerous types of active site due to the various physical or chemical structures originated from the amorphous silica support and various surface chromate species.…”

“…It is noted that the activity level continuously increased during the reaction, suggesting the 1-hexene comonomer as an activation agent may play a role. The comonomer could act as activation agent on the copolymerization of ethylene/1-hexene, [4,36,37] and ethylene/cyclopentene [38] over the Phillips CrO x /SiO 2 catalyst.…”