Silica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization

Handle URI:
http://hdl.handle.net/10754/562903
Title:
Silica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization
Authors:
Atiqullah, Muhammad; Anantawaraskul, Siripon; Emwas, Abdul-Hamid M.; Al-Harthi, Mamdouh Ahmed; Hussain, Ikram; Ul-Hamid, Anwar; Hossaen, Anwar
Abstract:
Metallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts-silica/MAO/(nBuCp)2ZrCl2 (Catalyst 1) and silica/nBuSnCl3/MAO/(nBuCp)2ZrCl2 (Catalyst 2), where MAO is methylaluminoxane-were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene-1-hexene Copolymer 1 and Copolymer 2, respectively. Fouling-free copolymerization, catalyst kinetic stability and production of free-flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self-nucleation and annealing experiments, as well as by an extended X-ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO-pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co-monomer effect-both by 1-hexene-were common. Each copolymer demonstrated vinyl, vinylidene and trans-vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction of the present work, is recommended. © 2013 Society of Chemical Industry.
KAUST Department:
Advanced Nanofabrication, Imaging and Characterization Core Lab
Publisher:
Wiley-Blackwell
Journal:
Polymer International
Issue Date:
12-Aug-2013
DOI:
10.1002/pi.4587
Type:
Article
ISSN:
09598103
Sponsors:
The authors acknowledge the financial support provided by King Abdulaziz City for Science and Technology (KACST) via the Science & Technology Unit at King Fahd University of Petroleum & Minerals (KFUPM) through project number 08-PET90-4 as part of the National Science and Technology Innovation Plan. The technical assistance provided by the following is also gratefully acknowledged: the KFUPM centers Center for Refining & Petrochemicals (CRP), Center for Engineering Research at Research Institute and the Center of Research Excellence in Petroleum Refining & Petrochemicals (CoRE-PRP), Dhahran, Saudi Arabia; NMR Core Laboratory, Thuwal, King Abdullah University of Science & Technology (KAUST), Saudi Arabia; the Department of Chemical Engineering at KFUPM; and the Department of Chemical Engineering at Kasetsart University, Thailand. The technical assistance of Mr Sagir Adamu is also appreciated.
Appears in Collections:
Articles; Advanced Nanofabrication, Imaging and Characterization Core Lab

Full metadata record

DC FieldValue Language
dc.contributor.authorAtiqullah, Muhammaden
dc.contributor.authorAnantawaraskul, Siriponen
dc.contributor.authorEmwas, Abdul-Hamid M.en
dc.contributor.authorAl-Harthi, Mamdouh Ahmeden
dc.contributor.authorHussain, Ikramen
dc.contributor.authorUl-Hamid, Anwaren
dc.contributor.authorHossaen, Anwaren
dc.date.accessioned2015-08-03T11:14:47Zen
dc.date.available2015-08-03T11:14:47Zen
dc.date.issued2013-08-12en
dc.identifier.issn09598103en
dc.identifier.doi10.1002/pi.4587en
dc.identifier.urihttp://hdl.handle.net/10754/562903en
dc.description.abstractMetallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts-silica/MAO/(nBuCp)2ZrCl2 (Catalyst 1) and silica/nBuSnCl3/MAO/(nBuCp)2ZrCl2 (Catalyst 2), where MAO is methylaluminoxane-were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene-1-hexene Copolymer 1 and Copolymer 2, respectively. Fouling-free copolymerization, catalyst kinetic stability and production of free-flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self-nucleation and annealing experiments, as well as by an extended X-ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO-pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co-monomer effect-both by 1-hexene-were common. Each copolymer demonstrated vinyl, vinylidene and trans-vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction of the present work, is recommended. © 2013 Society of Chemical Industry.en
dc.description.sponsorshipThe authors acknowledge the financial support provided by King Abdulaziz City for Science and Technology (KACST) via the Science & Technology Unit at King Fahd University of Petroleum & Minerals (KFUPM) through project number 08-PET90-4 as part of the National Science and Technology Innovation Plan. The technical assistance provided by the following is also gratefully acknowledged: the KFUPM centers Center for Refining & Petrochemicals (CRP), Center for Engineering Research at Research Institute and the Center of Research Excellence in Petroleum Refining & Petrochemicals (CoRE-PRP), Dhahran, Saudi Arabia; NMR Core Laboratory, Thuwal, King Abdullah University of Science & Technology (KAUST), Saudi Arabia; the Department of Chemical Engineering at KFUPM; and the Department of Chemical Engineering at Kasetsart University, Thailand. The technical assistance of Mr Sagir Adamu is also appreciated.en
dc.publisherWiley-Blackwellen
dc.subjectEnd-group unsaturationen
dc.subjectEthylene-1-hexene copolymerizationen
dc.subjectMAO cage structureen
dc.subjectMWD and CCD deconvolutionen
dc.subjectSchulz-Flory/ Stockmayer active center distributionen
dc.subjectSegregation effectsen
dc.subjectSSA fractionationen
dc.subjectSupported metallocene catalysten
dc.titleSilica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerizationen
dc.typeArticleen
dc.contributor.departmentAdvanced Nanofabrication, Imaging and Characterization Core Laben
dc.identifier.journalPolymer Internationalen
dc.contributor.institutionCenter for Refining and Petrochemicals, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabiaen
dc.contributor.institutionCenter of Research Excellence in Petroleum Refining and Petrochemicals, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabiaen
dc.contributor.institutionDepartment of Chemical Engineering, Kasetsart University, Bangkok, 10900, Thailanden
dc.contributor.institutionDepartment of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabiaen
dc.contributor.institutionCenter for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabiaen
kaust.authorEmwas, Abdul-Hamid M.en
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