Dynamics of fragmentation of catalyst carriers in catalytic polymerization of olefins

Horackova, Blanka; Grof, Zdeněk; Košek, Juraj

doi:10.1016/j.ces.2007.03.022

Cited by 49 publications

(35 citation statements)

References 21 publications

(28 reference statements)

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“…[9][10][11][12] Employing supported rather than homogeneous catalysts during olefin polymerization effectively prevents reactor fouling. [12][13][14][15][16][17][18][19][20][21] The same could well be true during ethylene oligomerization. While the immobilization of single-site catalysts for olefin polymerization is well-documented in the literature, immobilization of oligomerization catalysts has hardly been addressed.…”

Section: Introductionmentioning

confidence: 96%

Effect of Aluminum Alkyls on a Homogeneous and Silica-Supported Phenoxy-Imine Titanium Catalyst for Ethylene Trimerization

2015

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A phenoxy-imine titanium catalyst (FI-catalyst) for selective ethylene trimerization was immobilized on MAO-pretreated silica and its activity and selectivity was compared with that of the corresponding homogeneous catalyst system. The homogeneous and heterogeneous ethylene oligomerization was conducted in the presence of different aluminum alkyls, commonly used as scavengers during olefin polymerization to remove residual oxygen and moisture from the reaction medium. Both the homogeneous and heterogeneous catalysts were strongly affected by the presence of scavenger in the reaction medium. Upon activation with R 3 Al/MAO (R= Et, nOct, iBu), the homogeneous catalyst switches selectivity from ethylene trimerization to polymerization. NMR spectroscopic investigations indicate that this change of selectivity can be attributed to ligand exchange between the pre-catalyst and the aluminum alkyl. The thereby formed ligand-free titanium alkyls act as polymerization catalysts and are responsible for the increasing polymer formation. Using the heterogeneous catalyst, the scavenger employed during ethylene trimerization was found to be of crucial influence regarding the activity of the catalyst and the occurrence of reactor fouling. Employing aluminum alkyls like iBu 3 Al and nOct 3 Al resulted in catalyst leaching and homogeneous polymer formation. The latter was prevented using Me 3 Al or Et 3 Al as scavenger, however, in general the supported catalyst was poisoned by aluminum alkyls, resulting in a low overall activity. It was found to be beneficial for the heterogeneous trimerization system to employ silica-supported scavengers. By physical separation of the catalyst and the scavenger this poisoning effect was effectively prevented, resulting in a highly active heterogeneous catalyst.

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Section: Introductionmentioning

confidence: 96%

Effect of Aluminum Alkyls on a Homogeneous and Silica-Supported Phenoxy-Imine Titanium Catalyst for Ethylene Trimerization

2015

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“…Particle growth during polymerization starts by a very fast catalyst fragmentation into a huge number of small fragments, which are dispersed in the polymer particle. [18][19][20] Subsequently polymer grows around each catalyst fragment. In other words, due to the replication effect it is possible to control the morphology of polyolefi n particles by the suitable choice of the catalyst.…”

Section: Introductionmentioning

confidence: 99%

Formation and Distribution of Rubbery Phase in High Impact Poly(propylene) Particles

Smolná

Gregor

Buráň

et al. 2016

Macromol. Mater. Eng.

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in inducing crazing and/or shear yield of the isotactic poly(propylene) (iPP) matrix. However, if the dimension of the rubbery domain in the iPP matrix is smaller than the size of the fracture ligament curvature then the rubbery domain is not able to stop the crack propagation. Thus, Jang et al. suggested that the optimal size of EPR domain is 0.5 μm. [ 2 ] The regular hiPP powder morphology (i.e., regular particle shape, narrow particle size distribution, homogeneous distribution of EPR phase in iPP matrix) contributes to the high reactor throughput and good hiPP powder processability. Many works focus on the morphology of the fi nal hiPP material in the molded or extruded form [3][4][5][6][7] but the characteristic application properties of hiPP are strongly infl uenced directly in the polymerization process. Although a number of papers dealing with the particle morphology after the fi rst (homopolymerization) stage [8][9][10][11] and after the second (copolymerization) stage [11][12][13][14][15][16][17] were published, important questions related to hiPP particle multiphase morphology and its evolution are still open. This paper reconstructs the principle of rubber incorporation in high impact poly(propylene) (hiPP) particles. The detailed information about the pores and rubber distribution inside and on the surface of hiPP particles is obtained by micro-computed tomography and atomic force microscopy. The strong effect of homopolymer origin on hiPP particle morphology and rubber distribution is demonstrated. To obtain the most homogeneous rubber distribution, the low homopolymer porosity is required. The initial particle porosity has a negligible effect on the thickness of the rubber layer on the particle surface at the medium rubber content. The rubber forms not only along the iPP primary particles and directly or close to the pores but also on or close to the particle surface rather than it fl ows there. The evidence for these claims is based on the systematic investigation in dependence on EPR content, homopolymer particle porosity (prepared by different catalysts) and antistatic agent deactivating catalyst close to particle surface.

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“…Kosek and co‐workers modeled the fragmentation process using the concept of “microelements.” This work proposed detailed stress‐based models of the development of morphology in a growing polymer particle. The particle and more precisely a limited portion of the catalyst/polymer particle (such as a pore or a set of pores) was observed in the early stage of its evolution.…”

Section: Fragmentation Processmentioning

confidence: 99%

Section: Fragmentation Processmentioning

confidence: 99%

Particle Growth during the Polymerization of Olefins on Supported Catalysts. Part 2: Current Experimental Understanding and Modeling Progresses on Particle Fragmentation, Growth, and Morphology Development

Alizadeh

McKenna

2017

Macro Reaction Engineering

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The morphology of the growing polymer particles is important in olefin polymerisation on supported catalysts. It has a significant impact on the rate of mass and energy transport, and consequently on the polymerisation rate, comonomer incorporation, and the molecular weight distribution. The ability to quantify the evolution of morphology during the polymerisation process à priori would therefore be quite useful. The morphology itself is a direct product of the fragmentation step and concurrent/subsequent expansion of the particle, both caused by the build‐up and dissipation of hydraulic forces due to the accumulation of polymer in the particle. It is influenced by the initial morphology of the support, as well as the reaction conditions and local polymer properties. The single particle models developed to describe the morphology evolution in a growing particle are reviewed here. The main assumptions, abilities, and limitations of the models are evaluated and the issues which face developing a completely predictive model are finally discussed. Despite some very interesting attempts at morphology modelling in recent years, significant progress still needs to be made in order to develop a fully predictive model of the sort.

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Dynamics of fragmentation of catalyst carriers in catalytic polymerization of olefins

Cited by 49 publications

References 21 publications

Effect of Aluminum Alkyls on a Homogeneous and Silica-Supported Phenoxy-Imine Titanium Catalyst for Ethylene Trimerization

Effect of Aluminum Alkyls on a Homogeneous and Silica-Supported Phenoxy-Imine Titanium Catalyst for Ethylene Trimerization

Formation and Distribution of Rubbery Phase in High Impact Poly(propylene) Particles

Particle Growth during the Polymerization of Olefins on Supported Catalysts. Part 2: Current Experimental Understanding and Modeling Progresses on Particle Fragmentation, Growth, and Morphology Development

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