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dc.contributor.authorAtiqullah, Muhammad
dc.contributor.authorAnantawaraskul, Siripon
dc.contributor.authorEmwas, Abdul-Hamid M.
dc.contributor.authorAl-Harthi, Mamdouh Ahmed
dc.contributor.authorHussain, Ikram
dc.contributor.authorUl-Hamid, Anwar
dc.contributor.authorHossaen, Anwar
dc.date.accessioned2015-08-03T11:14:47Z
dc.date.available2015-08-03T11:14:47Z
dc.date.issued2013-08-12
dc.identifier.issn09598103
dc.identifier.doi10.1002/pi.4587
dc.identifier.urihttp://hdl.handle.net/10754/562903
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.
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.
dc.publisherWiley
dc.subjectEnd-group unsaturation
dc.subjectEthylene-1-hexene copolymerization
dc.subjectMAO cage structure
dc.subjectMWD and CCD deconvolution
dc.subjectSchulz-Flory/ Stockmayer active center distribution
dc.subjectSegregation effects
dc.subjectSSA fractionation
dc.subjectSupported metallocene catalyst
dc.titleSilica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization
dc.typeArticle
dc.contributor.departmentImaging and Characterization Core Lab
dc.contributor.departmentAdvanced Nanofabrication, Imaging and Characterization Core Lab
dc.identifier.journalPolymer International
dc.contributor.institutionCenter for Refining and Petrochemicals, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia
dc.contributor.institutionCenter of Research Excellence in Petroleum Refining and Petrochemicals, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia
dc.contributor.institutionDepartment of Chemical Engineering, Kasetsart University, Bangkok, 10900, Thailand
dc.contributor.institutionDepartment of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia
dc.contributor.institutionCenter for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia
kaust.personEmwas, Abdul-Hamid M.
dc.date.published-online2013-08-12
dc.date.published-print2014-06


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