scholarly journals Modification of the Acyl Chloride Quench-Labeling Method for Counting Active Sites in Catalytic Olefin Polymerization

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 683
Author(s):  
Haoyang Yang ◽  
Biao Zhang ◽  
Wentao Zhong ◽  
Zhisheng Fu ◽  
Zhiqiang Fan
Keyword(s):  
Active Sites ◽  
Olefin Polymerization ◽  
Acyl Chloride ◽  
Propylene Polymerization ◽  
Molar Ratio ◽  
Side Reactions ◽  
Carbonyl Chloride ◽  
Natta Catalyst ◽  
Chain Transfer Reaction ◽  
Labeling Method

The reliable and efficient counting of active sites in catalytic olefin polymerization has been realized by using acyl chloride as the quench-labeling agent. However, the molar ratio of acyl chloride to the alkylaluminum cocatalyst must be larger than 1 in order to completely depress side reactions between the quencher and Al-polymeryl that is formed via chain transfer reaction. In this work, a tetrahydrofuran/thiophene-2-carbonyl chloride (THF/TPCC) mixture was used as the quenching agent when counting the active sites of propylene polymerization catalyzed by MgCl2/Di/TiCl4 (Di = internal electron donor)-type Ziegler–Natta catalyst activated with triethylaluminum (TEA). When the THF/TEA molar ratio was 1 and the TPCC/TEA molar ratio was smaller than 1, the [S]/[Ti] ratio of the polymer quenched with the THF/TPCC mixture was the same as that quenched with only TPCC at TPCC/TEA > 1, indicating quench-labeling of all active sites bearing a propagation chain. The replacement of a part of the TPCC with THF did not influence the precision of active site counting by the acyl chloride quench-labeling method, but it effectively reduced the amount of acyl chloride. This modification to the acyl chloride quench-labeling method significantly reduced the amount of precious acyl chloride quencher and brought the benefit of simplifying polymer purification procedures after the quenching step.

POISONING OF ACTIVE SITES ON ZIEGLER-NATTA CATALYST FOR PROPYLENE POLYMERIZATION

2008 ◽  
Vol 26 (05) ◽  
pp. 547 ◽  
Author(s):  
Kitti Tangjituabun ◽  
Sang Yull Kim ◽  
Yuichi Hiraoka ◽  
Toshiaki Taniike ◽  
Minoru Terano ◽  
...  
Keyword(s):  
Active Sites ◽  
Propylene Polymerization ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

scholarly journals Development of Large-Scale Stopped-Flow Technique and its Application in Elucidation of Initial Ziegler–Natta Olefin Polymerization Kinetics

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1012 ◽  
Author(s):  
Ashutosh Thakur ◽  
Toru Wada ◽  
Patchanee Chammingkwan ◽  
Minoru Terano ◽  
Toshiaki Taniike
Keyword(s):  
Active Sites ◽  
Large Scale ◽  
Olefin Polymerization ◽  
Polymerization Kinetics ◽  
Propylene Polymerization ◽  
Time Range ◽  
Stopped Flow ◽  
Chemical Transformations ◽  
Polymerization Catalysis ◽  
Short Period

The stopped-flow (SF) technique has been extensively applied to study Ziegler–Natta (ZN) olefin polymerization kinetics within an extremely short period (typically <0.2 s) for understanding the nature of the active sites as well as the polymerization mechanisms through microstructure analyses of obtained polymers. In spite of its great applicability, a small amount of polymer that is yielded in a short-time polymerization has been a major bottleneck for polymer characterizations. In order to overcome this limitation, a large-scale SF (LSF) system has been developed, which offers stable and scalable polymerization over an expanded time range from a few tens milliseconds to several seconds. The scalability of the LSF technique has been further improved by introducing a new quenching protocol. With these advantages, the LSF technique has been effectively applied to address several unknown issues in ZN catalysis, such as the role of physical and chemical transformations of a catalyst on the initial polymerization kinetics, and regiochemistry of ZN propylene polymerization. Here, we review the development of the LSF technique and recent efforts for understanding heterogeneous ZN olefin polymerization catalysis with this new system.

Calculation of Kinetic Parameters and Active Sites Concentration for a New Multiple Site Model in Bulk Propylene Polymerization with the MgCl -Supported Ziegler-Natta Catalyst Using the Genetic Algorithm Method

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Saeed Pourmahdian ◽  
Miaad Ghanbari
Keyword(s):  
Genetic Algorithm ◽  
Kinetic Parameters ◽  
Active Sites ◽  
Great Accuracy ◽  
Experimental Results ◽  
Propylene Polymerization ◽  
Site Model ◽  
Individual Site ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

A comprehensive triple-site-model was studied. This model was based on the new molecular dynamics outcomes obtained from the researchers on the different active sites that exist on the heterogeneous Ziegler-Natta catalyst. The model was composed of high-isospecific site (IS), low-isospecific site (IS), and aspecific site (AS). A transformation occurred on the high isotactic site and a second isotactic site was generated, as the low-isospecific site. The model is able to predict experimental results of bulk propylene polymerization with great accuracy. Moreover, the kinetic parameters and constants for each individual site has an Arrhenius type behavior. These parameters were determined using genetic algorithm adaptation method. The concentration of each type of sites, the isotactic and atactic fraction were determined during the polymerization, per unit mass of catalyst. A very good agreement was found in between the model and reported experimental results.

scholarly journals A Comparative Study of AlCl3and FeCl2-Modified TiCl4/MgCl2/THF Catalytic System in the Presence of Hydrogen for Ethylene Polymerization

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Thanyathorn Niyomthai ◽  
Aniroot Ratchadaphet ◽  
Bunjerd Jongsomjit ◽  
Piyasan Praserthdam
Keyword(s):  
Lewis Acids ◽  
Ethylene Polymerization ◽  
Active Sites ◽  
Molar Ratio ◽  
Acid Modification ◽  
Polymer Properties ◽  
Acidic Sites ◽  
Hydrogen Response ◽  
Chain Transfer Reaction ◽  
Activity Enhancement

Ethylene homopolymerization over TiCl4/MgCl2/THF catalysts modified with different metal halide additives (AlCl3and FeCl2) with and without hydrogen was investigated based on catalytic activity and polymer properties. Lewis acid modification can improve activity because it can remove the remaining THF in the final catalyst, which can poison the catalyst active sites via the ring-opening of THF that was confirmed by XRD measurements. Moreover, the activity enhancement was due to the formation of acidic sites by modifying the catalysts with Lewis acids. Thus, FeCl2doped catalyst (Fe-THF) exhibited the highest activity followed by AlCl3doped catalyst (Al-THF) and undoped catalyst (None-THF). In H2/C2H4molar ratio of 0.08, Fe-THF showed a better hydrogen response than Al-THF due to more titanium cluster distribution. Fe-THF is considered to have more clustered Ti species than Al-THF. As a consequence, it led us to obtain more possible chances to precede chain transfer reaction by hydrogen. The molecular weight, melting temperature, and crystallinity of obtained polymers were investigated by GPC and DSC measurement, respectively.

scholarly journals Multiplicity of Active-Site in Heterogeneous Ziegler-Natta Catalyst and Its Correlation with Polymer Microstructure

1970 ◽  
Vol 46 (4) ◽  
pp. 487-494
Author(s):  
ATM Kamrul Hasan
Keyword(s):  
Molecular Weight ◽  
Computer Simulation ◽  
Active Site ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Chain Structure ◽  
Surface Complexes ◽  
Polymer Microstructure ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Multiplicity of active-site in heterogeneous Ziegler-Natta catalysts and its correlation with polymer microstructure was studied through the surface structure analysis of catalyst by computer simulation of X-ray Photoelectron Spectroscopy (XPS) data and microstructure investigation of polypropylene chains based on the deconvolution of the molecular weight distribution curves by multiple Flory most probable distributions using Gel Permeation Chromatography (GPC) method. The number and relative intensities of these peaks were found correlated to the distribution of multiple active sites. In this investigation, four individual categories of active sites were identified, each of which yields polypropylene with unique properties of molecular weight and chain structure different from other active sites. The reason of the multiplicity of active sites was determined by the presence of different locations of surface titanium species coordinated with other surface atoms or molecules. These different surface complexes of active species determine the multiple active site nature of catalyst which replicates the microtacticity, molecular weight and chain microstructure distribution of polymer. Keywords: Ziegler-Natta catalyst; Multiple active sites; Flory components; Computer simulation; Deconvolution; MWD. DOI: http://dx.doi.org/10.3329/bjsir.v46i4.9596 BJSIR 2011; 46(4): 487-494

scholarly journals Determination of optimal reaction temperature and hydrogen amount for propylene polymerization by a mathematical model

2019 ◽  
Vol 68 (3-4) ◽  
pp. 119-127 ◽  
Author(s):  
Gholam Hossain Varshouee ◽  
Amir Heydarinasab ◽  
Ali Vaziri ◽  
Seyed Mehdi Ghafelebashi Zarand
Keyword(s):  
Reaction Temperature ◽  
Average Molecular Weight ◽  
Propylene Polymerization ◽  
Process Conditions ◽  
Adequate Model ◽  
Natta Catalyst ◽  
Optimal Reaction Temperature ◽  
The Relationship ◽  
Optimal Reaction

Regarding the complexity of Ziegler-Natta catalyst kinetics in polypropylene polymerization, so far, there is no adequate model to determine the best process conditions for predicting average molecular weight and dispersity as the most crucial final product properties index. Consequently, a validated model has been developed which describes the relationship between the kinetic model and the existing gap using the polymer moment balance approach. It was concluded that increasing reaction temperature and hydrogen amount are useful and improve the final product indices to a certain limit, but afterwards they have harmful effects on the indices.

Control of Ziegler–Natta catalyst activity by the structural design of alkoxysilane-based external donors

2020 ◽  
Vol 44 (17) ◽  
pp. 6845-6852 ◽  
Author(s):  
Vikas Khatri ◽  
Usharani Sahoo ◽  
Sukhdeep Kaur ◽  
Rashmi Rani ◽  
Gurmeet Singh ◽  
...  
Keyword(s):  
Structural Design ◽  
Catalyst Activity ◽  
Propylene Polymerization ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Herein, the evaluation of four commercial alkoxysilanes and two laboratory synthesized novel diethoxysilacycloalkanes as external donors towards propylene polymerization has been done.

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