Suppression of metallocene catalyst leaching by the removal of free trimethylaluminum from methylaluminoxane

Turunen, Jani P. J.; Pakkanen, Tuula T.

doi:10.1002/app.23120

Cited by 14 publications

(7 citation statements)

References 14 publications

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“…Different zirconocene aluminohydrides supported on silica produced very active systems (50–90 ton PE/molZr‐hr), using MAO as co‐catalyst, however the leaching of the catalysts was very evident because fine particles produced in the reactors caused fouling . According to several reports about studies of leaching in supported metallocenes, the trimethylaluminum (TMA) (always present in commercial MAO solutions) is highly reactive towards the SiO bonds of silica, causing fragmentation of the supported catalyst, and increasing the leaching of the catalysts . On the other hand, the use of silica as support for metallocene catalysts is restricted by several patents, which has motivated searching for alternative methods for using metallocenes and derivatives such as the zirconocene aluminohydrides for application to coordination polymerization in slurry.…”

Section: Introductionmentioning

confidence: 99%

Zirconocene Aluminohydride‐Methylaluminoxane Clathrates for Ethylene Polymerization in Slurry

Padilla‐Gutiérrez

Ventura‐Hunter²,

García-Zamora³

et al. 2017

Macromolecular Symposia

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The main aim of this work is to obtain heterogeneous, zirconocene aluminohydride/methylaluminoxane (MAO) polymerization catalysts, without using inorganic carriers like silica. The syntheses of zirconocenium ion‐based clathrates, formed from aluminohydride zirconocene complexes activated with MAO, are reported here. Several different approaches were examined for the synthesis of these clathrate compositions; in one approach the catalyst (nBuCp2ZrH3AlH2/MAO) was first prepared in toluene solution, and the clathrate phase then generated by addition of silicone oil. An alternate approach involved reaction of silicone oil or another clathrate‐forming additive (e.g. KCl) with MAO to form a solidified clathrate, and then introducing the zirconocene aluminohydride complex (nBuCp2ZrH3AlH2). The clathrate catalysts were probed in the polymerization of ethylene in hydrocarbon slurry, without using additional co‐catalyst (MAO), or at very low concentrations of modified MAO (MMAO 7, 13 wt‐% in iso‐octane). The catalytic activities of the solid clathrate catalysts were compared as well as the morphology and properties of the polyethylene synthesized in slurry.

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Section: Introductionmentioning

confidence: 99%

Zirconocene Aluminohydride‐Methylaluminoxane Clathrates for Ethylene Polymerization in Slurry

Padilla‐Gutiérrez

Ventura‐Hunter²,

García-Zamora³

et al. 2017

Macromolecular Symposia

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“…Similarly to the behavior of the homogeneous polymerizations with the S 1 catalyst, the use of hydrogen in the polymerizations led to higher activities, but in the heterogeneous case several peaks in the kinetic curve are observed (Figure ), suggesting that more than one active species could be present in the polymerization reaction. For supported catalysts the desorption or lixiviation of the metallocene has been widely reported as a drawback, promoting simultaneous polymerization in the supported catalyst (heterogeneous) and in solution (homogeneous). In the kinetic behavior depicted in Figure , the first peak (1000 s) could be attributed to the heterogenized catalyst, which it is then desorbed to the continuous phase, showing another peak at around 3000 s.…”

Section: Resultsmentioning

confidence: 99%

Kinetic monitoring methods for ethylene coordination polymerization in a laboratory reactor

Infante

Saldívar‐Guerra

Pérez‐Camacho

et al. 2013

J of Applied Polymer Sci

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The kinetic performance of metallocene type catalysts as well as their instantaneous activity is determined on line by two independent methods in the semi-batch polymerization of ethylene via metallocenes. The first-principle basis of both methods is described and guidelines for their implementation at a laboratory scale reactor are offered. Polymerization tests were conducted with two heterogenized metallocene catalysts showing that the direct method (based on ethylene flow measurement) and the calorimetric method (based on energy balances and developed here) report equivalent high quality information. This last method can be readily used by the chemical practitioner as the notions and tools required for its implantation are easily grasped; it also has the advantage of requiring a low cost instrumentation (only thermocouples), whereas the direct method needs a relatively more sophisticated equipment (mass flow meter).

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“…[19,20,47] 7) Metallocene complexed with surface-immobilized MAO may degenerate and leach away from the surface to the liquid phase in the silica pores. [8,48,49]…”

Section: Mathematical Modelmentioning

confidence: 99%

Effect of Intraparticle Mass Transfer on the Catalytic Site Formation in the Preparation of Silica‐Supported Metallocene Catalysts

Tran

Sowah

Choi

2021

Macro Reaction Engineering

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The preparation conditions of silica-supported metallocene catalysts impact the catalytic performance and consistency in ethylene polymerization. In a commonly used catalyst impregnation technique, the concentrations of catalyst solutions and the contact time between silica microparticles and catalyst solutions are used to ensure uniform and stable immobilization of coactivator methyl aluminoxane (MAO) and metallocenes. The overall catalytic activities for olefin polymerization, catalyst particle fragmentation, and the resulting polymer particle morphology depend upon the distribution of active catalyst sites within the silica catalyst particle. This work presents both experimental and theoretical modeling studies on the intraparticle spatial distribution of MAO and metallocene in highly porous silica microparticles for ethylene polymerization in a liquid-slurry phase. The silica-catalyst solution contact times and the catalyst solution concentrations are used as two major variables to vary the intraparticle catalyst site distributions. The overall aluminum and zirconium contents in the catalyst and their radial distributions are observed to be strongly affected by the impregnation conditions. A mathematical model is also derived for the catalyst impregnation process and it provides adequate predictions of the impregnation process characteristics.

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Suppression of metallocene catalyst leaching by the removal of free trimethylaluminum from methylaluminoxane

Cited by 14 publications

References 14 publications

Zirconocene Aluminohydride‐Methylaluminoxane Clathrates for Ethylene Polymerization in Slurry

Zirconocene Aluminohydride‐Methylaluminoxane Clathrates for Ethylene Polymerization in Slurry

Kinetic monitoring methods for ethylene coordination polymerization in a laboratory reactor

Effect of Intraparticle Mass Transfer on the Catalytic Site Formation in the Preparation of Silica‐Supported Metallocene Catalysts

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