Development of novel chromium oxide/metallocene hybrid catalysts for bimodal polyethylene

Moreno, Jovita; Grieken, Rafael van; Carrero, A.; Paredes, Beatriz

doi:10.1016/j.polymer.2011.02.048

Cited by 29 publications

(30 citation statements)

References 32 publications

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“…Such versatility has provoked many researches for simultaneous application of Ziegler-Natta or Phillips catalysts with metallocenes having new characteristics. Examples mainly include production of bimodal MWD by hybrid catalyst (both catalysts supported on the same support) [19][20][21][22][23]. Further, application of mixed homogenous and/or heterogeneous dual metallocene systems or the corresponding hybrid catalysts was seen to have more flexibility for control of chain microstructure [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Mortazavi

Jafarian

Ahmadi

et al. 2015

J Therm Anal Calorim

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Nickel diimine late transition metal (LTM) and Cp 2 TiCl 2 metallocene catalysts were supported on the TIBA-modified MgCl 2 ÁnEtOH adduct, separately and concurrently, at different ratios, to yield hybrid catalysts, where the catalytic precursors were activated in the ethylene polymerization with TEA as the cocatalyst. Polymerization activities revealed that supported LTM catalysts show very high levels of activity, in an adverse trend with polymerization temperature ranging from 30 to 70°C, in opposition to the activity of metallocene component. Consequently, the proportion of corresponding polymer fractions were tuned by changing reaction temperature as well as catalyst composition. Study of thermal properties confirmed that LTM component is responsible for production of less crystallizable branched chains, while metallocene fraction makes highly crystallizable linear chains. All samples showed noticeable thermorheological complexity due to coexistence of linear and branched microstructures. Interestingly, it was found that increase in metallocene fraction of the hybrid catalyst stalls the terminal relaxation of the produced polymers and increases the entanglement density by decreasing the extent of branching. Study of dynamic mechanical properties revealed that the intensity of b transition could be correlated with the branching level and catalyst composition accordingly.

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Section: Introductionmentioning

confidence: 99%

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Mortazavi

Jafarian

Ahmadi

et al. 2015

J Therm Anal Calorim

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“…Other alternatives involving the usage of hybrid catalysts with two or more catalytic systems on a support (e.g. metallocene‐chromium over silica or SBA‐15 or polymer coated hybrid catalysts have also led toward bimodal polyethylenes. However, these hybrid systems are more difficult to tailor to the desired products and result in added operational complexity.…”

Section: Resultsmentioning

confidence: 99%

Ethylene Polymerization Over Ph₂C(Cp)(2,7‐t‐Bu₂Flu)ZrCl₂ Supported On SiO₂‐MAO

Casas

Paredes

Escola

et al. 2013

Macro Reaction Engineering

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Ethylene polymerization over heterogeneous [Ph2C(Cp)(2,7‐t‐Bu2Flu)ZrCl2] supported on SiO2‐MAO is studied. The influence of the main reaction variables is determined in ethylene homopolymerization: TEA concentration (88–702 ppm), temperature (55–85 °C) and pressure (3–12 bar). An optimum in the catalytic activity is achieved at TEA a concentration of 351 ppm, 85 °C and 8 bar of ethylene. At this ethylene pressure, all the polyethylenes show molecular weights above 400 000 g · mol−1. Using hydrogen as transfer agent, the activity is distinctly lower but it is possible to attain molecular weights below 40 000 g · mol−1. Regarding 1‐butene, it is observed good catalytic response in copolymerization, observing remarkable activities, higher than those obtained in homopolymerization.

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“…[14][15][16] A few studies concerning the combination of chromium-based with nonchromium based catalysts were also published. [17][18][19][20][21][22] Following this trend, a novel SiO 2 -supported Cr-V bimetallic catalyst was prepared by using the residual surface hydroxyl groups in a SiO 2 -supported vanadium catalyst to support bis(triphenysilyl) chromate in our previous work. [23] Compared with the silyl-chromate (S-2) catalyst which is synthesized by supporting bis(triphenysilyl) chromate separately on silica, the resulting PE made by the Cr-V bimetallic catalyst showed higher molecular weight (MW) and bimodal MWD, while ethylene/1-hexene copolymers also exhibited a better short-chain branch distribution (SCBD).…”

Section: Doi: 101002/mren201700059mentioning

confidence: 99%

Effect of Alkyl Aluminums on Ethylene Polymerization Reactions with a Cr‐V Bimetallic Catalyst

Bao

Tian

Jin

et al. 2018

Macro Reaction Engineering

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The effect of introducing various types of alkyl aluminums directly into the catalyst and/or in the polymerization process as cocatalyst on the efficiency of a Cr‐V bimetallic catalyst for ethylene polymerization is systematically investigated. Results indicate that polymerization activity, kinetic behavior, and polymer properties of the Cr‐V catalyst are strongly affected by using alkyl aluminums in different stages of polymerization, due to the different responses and sensitivities of the two metal centers to alkyl aluminum. When employed as cocatalyst, triisobutyl aluminum gives high activity and polyethylene with relatively low molecular weight, while diethylaluminum chloride cocatalyzes the production of ultra‐high molecular weight polyethylene but with very low activity. On the other hand, the pre‐reduction of the bimetallic catalyst by alkyl aluminums has a marked promotion effect on catalyst efficiency. It is suggested that the addition of alkyl aluminum to the catalyst and to the reactor as cocatalyst are more or less equivalent in their effects on the improvement of polymerization activity, but they behave in different ways to affect polymer properties.

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Development of novel chromium oxide/metallocene hybrid catalysts for bimodal polyethylene

Cited by 29 publications

References 32 publications

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Ethylene Polymerization Over Ph₂C(Cp)(2,7‐t‐Bu₂Flu)ZrCl₂ Supported On SiO₂‐MAO

Effect of Alkyl Aluminums on Ethylene Polymerization Reactions with a Cr‐V Bimetallic Catalyst

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Development of novel chromium oxide/metallocene hybrid catalysts for bimodal polyethylene

Cited by 29 publications

References 32 publications

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Ethylene Polymerization Over Ph2C(Cp)(2,7‐t‐Bu2Flu)ZrCl2 Supported On SiO2‐MAO

Effect of Alkyl Aluminums on Ethylene Polymerization Reactions with a Cr‐V Bimetallic Catalyst

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Ethylene Polymerization Over Ph₂C(Cp)(2,7‐t‐Bu₂Flu)ZrCl₂ Supported On SiO₂‐MAO