Ziegler–Natta catalysts supported on crystalline and amorphous MgCl2/THF complexes

Pirinen, Sami; Jayaratne, Kumudini C.; Denifl, Peter; Pakkanen, Tuula T.

doi:10.1016/j.molcata.2014.09.013

Cited by 19 publications

(15 citation statements)

References 27 publications

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“…As a matter of fact, the distribution of the active phase has already been proved to depend on the relative extent of the surfaces exposing either 4-fold coordinated Mg 2 + sites, as the (110) surface, or 5-fold coordinated Mg 2 + sites, as the (104) one. [32,[46][47][48][49][50][51][52][53][54][55] The latter method was recently proved to promote the formation of MgCl 2 nanocrystals whose morphologies depend on the starting alcoholic adduct. [32,[46][47][48][49][50][51][52][53][54][55] The latter method was recently proved to promote the formation of MgCl 2 nanocrystals whose morphologies depend on the starting alcoholic adduct.…”

Section: Introductionmentioning

confidence: 99%

Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

et al. 2018

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Ziegler-Natta catalysts for olefin polymerization are intrinsically complex multi-component systems. The genesis of the active sites involves several simultaneous and sequential steps, making the individual steps and interconnections difficult to be unraveled in an unambiguous manner. In this work, we combine X-ray diffraction and spectroscopy to probe each step of the birth and life of a MgCl -based Ziegler-Natta catalyst, namely the formation of high surface area MgCl by dealcoholation of an alcoholate precursor, the TiCl grafting, and the subsequent activation by triethylaluminum as co-catalyst. The so-prepared catalyst was tested towards ethylene polymerization, leading to the production of mainly crystalline high-density polyethylene. The use of operando characterization techniques allowed probing the transient details that are difficult to be dissected in the aftermath, but can radically affect the overall catalytic process.

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Section: Introductionmentioning

confidence: 99%

Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

et al. 2018

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“…5,7,8,[29][30][31] In our previous works we have demonstrated the potential of a multi-technique approach in unraveling the nature of the active TiCl x phase in catalysts obtained by reacting together titanium and magnesium chloride tetrahydrofuranate precursors and the aluminum-alkyl activator. 7,8 The investigation is more complex when the TiCl x and MgCl x phases are simultaneously supported on dehydroxylated silica in presence of tetrahydrofuran.…”

Section: Introductionmentioning

confidence: 99%

Activation and In Situ Ethylene Polymerization on Silica-Supported Ziegler–Natta Catalysts

et al. 2015

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The structural, vibrational and electronic properties of silica-supported Ziegler-Natta catalysts industrially relevant for polyethylene production were investigated in details by means of a multi-technical approach, at each step of catalyst preparation -including pre-catalyst activation. In the pre-catalyst, the TiCl x phase is mainly grafted to the silica surface, and almost independent of the supported MgCl x phase. However, the subsequent activation by means of an aluminum-alkyl compound causes important changes to both, the supported MgCl x phase and the TiCl x phase. The resulting catalyst is entirely reconstructed, so that most of the titanium sites are detached from the silica surface and in interaction with a highly dispersed MgCl 2 phase, thus mimicking the most famous and highly investigated Ziegler-Natta catalysts (not silica-supported). For the first time, the catalyst performances were monitored by means of in situ FT-IR spectroscopy in transmission mode, simulating industrially significant polymerization conditions (i.e. ethylene is fed onto the catalyst in the presence of the activator and of the solvent). These results demonstrate that it is now possible to achieve a complete description at a molecular level of all the constituents of Ziegler-Natta catalysts, at each step of the catalyst preparation.

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“…There are some articles reported that the complex of TiCl 4 /MgCl 2 with THF showed IR bands in the range of 1100–700 cm −1 , indicating the most sensitive to THF complexes with a metal center . In general, pure THF has the symmetrical and an asymmetrical C–O–C stretching bands around 913 cm −1 and 1071 cm −1 , respectively . However, ZN‐THF exhibits these two peaks, which are the symmetrical and the asymmetrical C–O–C stretching bands of THF around 883.4 cm −1 and 1032.6 cm −1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Influence of Hydrogen on Catalytic Properties of Ziegler‐Natta Catalysts Prepared by Different Methods in Ethylene Polymerization

et al. 2016

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Ethylene homopolymerization by two types of Ziegler-Natta catalyst including ZN-THF and ZN-EtOH catalysts was compared. The influences of hydrogen pressure and reaction time on catalytic activity using different types of catalyst were investigated. The EDX analysis and surface area measurement confirmed that ZN-EtOH catalyst had better active center distribution than that of ZN-THF. Thus, the ZN-EtOH catalyst could retard the effect of hydrogen and show higher activity with increased hydrogen pressures. However, catalytic activity was lower with high hydrogen pressure. Moreover, polymerization time also has an influence on activity. Both catalysts showed the similar result where an increase in polymerization time can improve yield of polymer, but it decreased activity. In addition, it is seen that the increase in hydrogen pressure leads to decrease the melting temperature for polyethylenes, but it increases the crystallinity.

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Ziegler–Natta catalysts supported on crystalline and amorphous MgCl2/THF complexes

Cited by 19 publications

References 27 publications

Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

Activation and In Situ Ethylene Polymerization on Silica-Supported Ziegler–Natta Catalysts

Influence of Hydrogen on Catalytic Properties of Ziegler‐Natta Catalysts Prepared by Different Methods in Ethylene Polymerization

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Ziegler–Natta catalysts supported on crystalline and amorphous MgCl2/THF complexes

Cited by 19 publications

References 27 publications

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

Activation and In Situ Ethylene Polymerization on Silica-Supported Ziegler–Natta Catalysts

Influence of Hydrogen on Catalytic Properties of Ziegler‐Natta Catalysts Prepared by Different Methods in Ethylene Polymerization

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Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

Genesis of MgCl₂‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy