Ethylene/1‐Hexene Copolymerization with A Novel SiO 2 ‐Supported Inorganic and Organic Hybrid Chromium‐based Catalyst

et al. 2016

Macromol. React. Eng.

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MgCl 2 /TiCl 4 catalyst which was fi rst reported by Kashiwa [ 1 ] and Galli [ 2 ] independently in 1968. Anhydrous MgCl 2 was used as Mg-source, and excess amount of TiCl 4 removed the alcohol from MgCl 2 -alcoholate adduct and MgCl 2 was recrystallized simultaneously. This is a signifi cant innovation and greatly promotes the development of industrial polyolefi n processes. Another commercial MgCl 2 / TiCl 4 ZN catalyst was developed by Böhm, [ 3 ] and Mg(OEt) 2 as the Mg-source reacted with TiCl 4 directly to synthesize MgCl 2 support in situ. Later on, Union Carbide Corporation (UCC) also utilized anhydrous MgCl 2 as Mg-source and meanwhile introduced SiO 2 into the titanium-magnesium catalytic (TMC) system to develop a series of MgCl 2 /SiO 2 bi-supported ZN catalysts. The most famous MgCl 2 /SiO 2 ZN catalyst was M-1 catalyst and successfully applied in UNIPOL gas-phase polyethylene process. [ 4,5 ] Chamla [ 6 ] and Stevens [ 7 ] used alkyl magnesium (MgR 2 ) and Grignard reagents (RMgCl) as starting Mg-source, respectively, followed A novel vanadium-modifi ed (SiO 2 /MgO/MgCl 2 )·TiCl x Ziegler-Natta ethylene polymerization catalyst with much better catalytic performance is successfully developed. The catalyst is prepared by co-impregnation of aqueous solution of water-soluble magnesium and vanadium compounds on SiO 2 , and a supported thin layer of magnesium and vanadium oxides is formed over the surface of SiO 2 after high temperature calcination in dry air, followed by further reaction with titanium tetrachloride to synthesize the magnesium dichloride carrier in situ and to support the titanium species simultaneously. By characterization of the catalysts and the polymers and investigation of the polymerization behaviors, it is found that compared with the original (SiO 2 /MgO/MgCl 2 )·TiCl x ZN catalyst, the introduction of vanadium species induce improved catalytic performance with 27% higher activity, 48% higher hydrogen response, and 60% higher 1-hexene incorporation ability with better short chain branch distribution.

Section: The Comparison Of Scbd For Copolymers From Different Catalystsmentioning

confidence: 99%

Vanadium Modification Effects on the (SiO₂/MgO/MgCl₂)•TiCl_xZiegler-Natta Polyethylene Catalyst

Wang

et al. 2016

Macromol. React. Eng.

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“…The ethylene/1‐hexene copolymers were fractionated by a self‐made TREF system . The equipment included an 850 mL column type fractionation bottle (height: 156 mm; diameter: 84 mm) filled with quartz sand, a silicone oil bath with thermostat (Huber, POLYTSTAT CC2‐225B ± 0.02 °C), a pump (KNF Lab, STEPDOS 08 S), a rotary evaporator (EYELA) and a nitrogen gas container.…”

Section: Methodsmentioning

confidence: 99%

A Novel SiO₂‐Supported Fluorine Modified Chromium–Vanadium Bimetallic Catalyst for Ethylene Polymerization and Ethylene/1‐Hexene Copolymerization

Sun

Wang

Macro Reaction Engineering

et al. 2017

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Phillips catalyst is one of the most significant industrial ethylene polymerization catalysts. Chemical modifications have been carried out to tune the Phillips catalyst performance and improve the polyethylene properties. After the modification of the catalyst by fluorine, the polyethylene product with higher molecular weight (MW) and narrower molecular weight distribution (MWD) is suitable for producing automobile fuel tanks. Vanadium containing Phillips catalyst enhances α‐olefin incorporation and MW regulation. In present work, fluorine modified and unmodified chromium–vanadium (Cr–V) bimetallic catalysts are prepared and explored. Compared with the fluorine‐free catalyst, the activities of F‐modified bimetallic catalysts slightly decrease with the increasing MW of the product and the hydrogen response increases slightly. Due to the synergistic effect of the chromium, vanadium and fluorine on the silica gel support, the short‐chain branch distribution (SCBD) of copolymers from F‐modified Cr–V bimetallic catalyst (Cr–V–F)600 is more beneficial than that of Cr–V bimetallic catalyst (Cr–V)600 and F‐modified Cr–V bimetallic catalyst (Cr–V–F)500. The fluorination of Cr–V bimetallic catalysts has not only preserved the high polyethylene activity of bimetallic active sites but also produced the advantage of the high MW ability from fluorine.

“…This was similar to our previous report on the SiO 2 -supported inorganic and organic hybrid chromium-based catalyst. [23] It should be noted that a much sharper decrease in the kinetic profile associated to the fast formation and fast decay type. It was reported that the vanadium center in vanadium-based Ziegler-Natta polymerization system catalysts tended to rapidly deactivated due to overreduction to inactive lower oxidation states by Al-alkyl cocatalyst during the polymerization process.…”

Section: Ethylene Polymerization Behaviorsmentioning

confidence: 98%

“…The SCBD in the corresponding ethylene/1-hexene copolymer products was characterized by combination of temperature rising elution fractionation (TREF) with successive self-nucleation/annealing (SSA) as demonstrated in our previous reports. [23,35] 2. Experimental Section , and average pore size 24.5 nm) was donated by Qilu Branch Co., SINOPEC.…”

Section: Introductionmentioning

confidence: 99%

“…Preparative TREF was carried out using a home-made instrument developed by us. [23,35] About 1.2 g polymer was heated and fully dissolved in 200 mL of xylene in a three-necked flask with stirring for at least 2 h. The reactor was then transferred to a temperature-controlled oil bath and filled with pre-heated quartz sand (AR), used as a crystallization support. The sample was kept at 135 8C for 1 h and then cooled to 30 8C at a controlled rate of 5 8C Á h À1 to facilitate controlling the crystallization of the polymer.…”

mentioning

confidence: 99%

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

Macro Reaction Engineering

Xue

Liu

et al. 2015

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Novel SiO 2 -supported Cr-V bimetallic oxides catalysts, which were capable of one-pot synthesizing polyethylene with bimodal molecular weight distribution, had been successfully developed. These catalysts were prepared with a simple introduction of vanadium oxide onto the traditional Phillips CrO x /SiO 2 catalyst. The polymerization activity over the Cr-V bimetallic catalysts was significantly improved compared with the V-free Phillips CrO x /SiO 2 catalyst. Moreover, the bimodal ethylene/1-hexene copolymer prepared by the novel catalyst showed a better short chain branch distribution with more 1-hexene comonomer inserted into the PE chains with high molecular weight, which would be favorable for the long term mechanical properties of the bimodal PE as potential high grade pipe materials.