Morphological modifications of Cr/SBA-15 and Cr/Al-SBA-15 ethylene polymerization catalysts: Influence on catalytic behaviour and polymer properties

Aguado, J.; Calleja, Guillermo; Carrero, A.; Moreno, Jovita

doi:10.1016/j.micromeso.2010.01.006

Cited by 18 publications

(6 citation statements)

References 20 publications

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“…In the field of chromium‐based catalysts, McDaniel et al and Kurek et al prepared novel hybrid catalysts for producing polyethylene with ultra‐broad MWD through the usage of novel mesoporous silica gel to support a postmetallocene chromium complex and a half sandwich chromium complex. Moreno et al synthesized a novel silica–alumina–SBA‐15 material for the supporting of chromium(III) nitrate and metallocene zirconium complex to prepare chromium oxide/metallocene hybrid catalyst for producing bimodal polyethylene. In our previous work, we hybridized two famous chromium‐based catalysts named Phillips catalyst and S‐2 catalyst for producing polyethylene with broad MWD .…”

Section: Introductionmentioning

confidence: 99%

A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

Zhao

Cheng

et al. 2014

Macro Chemistry & Physics

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A novel SiO2‐supported Cr–V bimetallic catalyst for ethylene and ethylene/α‐olefin polymerization is investigated. This catalyst is prepared using the residual surface hydroxyl groups in a SiO2‐supported vanadium catalyst to support bis(triphenysilyl) chromate (BC) in order to get the merits from both the vanadium‐based catalyst and the S‐2 catalyst. By investigation of the polymerization behavior and the microstructures of their polymers, several vital factors, such as the addition amount of vanadium species and the dosage of 1‐hexene, on the ethylene/1‐hexene copolymerization are systematically investigated. The results show that the activity of each bimetallic catalyst is higher than that of the S‐2 catalyst, and the product from the bimetallic catalyst shows a higher molecular weight (MW) with a bimodal molecular weight distribution (MWD). The copolymers obtained using the bimetallic catalyst also show a better short‐chain branch distribution (SCBD) than that using the S‐2 catalyst through a temperature rising elution fractionation (TREF) cross successive self‐nucleation and annealing (SSA) characterization.

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Section: Introductionmentioning

confidence: 99%

A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

Zhao

Cheng

et al. 2014

Macro Chemistry & Physics

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“…In the field of chromium‐based catalysts, McDaniel et al and Kurek et al prepared a novel mesoporous silica gel to support a post‐metallocene chromium complex and a half sandwich chromium complex to prepare a hybrid catalyst and obtained ultra‐broad MWD PE product. Moreno et al synthesized a novel silica–alumina–SBA‐15 material for the supporting of chromium(III) nitrate and metallocene zirconium complex to prepare chromium oxide/metallocene hybrid catalyst for producing bimodal PE. In our previous work, we hybridized the two famous chromium‐based industrial catalysts namely the Phillips catalyst and the S‐2 catalyst for producing PE with broad MWD .…”

Section: Introductionmentioning

confidence: 99%

Novel SiO₂‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution

Zhao

Cheng

et al. 2014

Macro Chemistry & Physics

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Novel SiO 2 -supported silyl-chromate(Cr)/imido-vanadium(V) (Cr-imidoV) bimetallic catalysts for ethylene and ethylene/α-olefi n polymerization are investigated. These catalysts are prepared using the residual surface hydroxyl groups in SiO 2 -supported imido-vanadium catalysts to further support bis(triphenylsilyl) chromate (BC) in order to get the merits from both the SiO 2supported imido vanadium catalyst and the SiO 2 -supported silyl chromate S-2 catalyst. By investigation of the polymerization behavior and the microstructures of their polymers, several vital factors such as the addition amount of imido vanadium active centers and the dosage of 1-hexene in the ethylene homopolymerization and ethylene/ 1-hexene copolymerization are systematically investigated. Compared with the traditional S-2 catalyst and our previously reported SiO 2 -supported silyl-chromate(Cr)/vanadium(V)-oxide (Cr-V) bimetallic catalyst, the novel Cr-imidoV bimetallic catalysts show even higher activity and better 1-hexene incorporation ability, together with higher molecular weight (MW) and bimodal molecular-weight distribution (MWD).

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“…46 The forces induced by polymer formation (see the Supporting Information) can fracture pores with widths down to ca. 15 nm in silica, 47 and these fractures might lead to increased activity 48,49 by abstracting hydrogen atoms from ethylene or from polyethylene (see Figure S10 in the Supporting Information) to create alkyl and/or vinyl radicals. These radicals would readily interact with Cr II sites that have not yet been activated, converting them to polymerization-ready alkylCr III sites.…”

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confidence: 99%

Computational Support for Phillips Catalyst Initiation via Cr–C Bond Homolysis in a Chromacyclopentane Site

et al. 2018

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Using density functional theory, we examine a possible homolysis initiation mechanism for the Phillips catalyst, starting from CrII sites exposed to ethylene. Spin-crossing in an abundant quintet bis(ethylene) CrII site leads to cycloaddition to form a chromacyclopentane site. One Cr–C bond then homolyzes to generate a tethered n-butyl radical: [Cr(CH2)3CH2 •]. If the radical attaches to a nearby inorganic Cr site, it yields two alkylCrIII sites capable of Cossee–Arlman polymerization. The overall computed barrier for this initiation process is 132 kJ/mol, which is comparable to the 120 kJ/mol value that we estimated from reported initiation times in industrial reactors. Poisson statistics suggest that this mechanism could activate ∼35% of Cr sites on a commercial catalyst with a loading of 0.4 Cr/nm2. Pairwise Cr grafting, amplification by complementary initiation reactions, or the creation of dangling bonds that form as the silica support fractures, might explain the apparent increase in per-site activity at lower Cr loadings.

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Morphological modifications of Cr/SBA-15 and Cr/Al-SBA-15 ethylene polymerization catalysts: Influence on catalytic behaviour and polymer properties

Cited by 18 publications

References 20 publications

A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

Novel SiO₂‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution

Computational Support for Phillips Catalyst Initiation via Cr–C Bond Homolysis in a Chromacyclopentane Site

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Morphological modifications of Cr/SBA-15 and Cr/Al-SBA-15 ethylene polymerization catalysts: Influence on catalytic behaviour and polymer properties

Cited by 18 publications

References 20 publications

A Novel SiO2‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

A Novel SiO2‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

Novel SiO2‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution

Computational Support for Phillips Catalyst Initiation via Cr–C Bond Homolysis in a Chromacyclopentane Site

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A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

A Novel SiO₂‐Supported Cr–V Bimetallic Catalyst Making Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular Weight Distribution

Novel SiO₂‐Supported Silyl‐Chromate(Cr)/Imido‐Vanadium(V) Bimetallic Catalysts Producing Polyethylene and Ethylene/1‐Hexene Copolymers with Bimodal Molecular‐Weight Distribution