Catalysis
Goond Hongmanee; Patchanee Chammingkwan; Toshiaki Taniike; Minoru Terano
Abstract
Mg(OEt)2 with spherical morphology is one of the most important precursors for the preparation of industrial Ziegler-Natta catalysts. In the present article, morphology evolution of Mg(OEt)2 particles is studied in the course of the synthesis. The morphology of Mg(OEt)2 particles is observed throughout ...
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Mg(OEt)2 with spherical morphology is one of the most important precursors for the preparation of industrial Ziegler-Natta catalysts. In the present article, morphology evolution of Mg(OEt)2 particles is studied in the course of the synthesis. The morphology of Mg(OEt)2 particles is observed throughout the process by SEM. The results show that Mg(OEt)2 particles are formed through i) seed generation on Mg surfaces, ii) seed growth and isolation as independent particles, and iii) further growth and shaping into smoother and more spherical particles. The size of Mg sources greatly affects the rates of these processes to different extents. A larger size of Mg leads to slower seed formation and growth, and detachment of clustered seeds, making the final particles larger and less spherical, respectively. The crystal growth of Mg(OEt)2 is also affected by the size of Mg sources, which in turn differentiates the pore size distribution to affect the catalyst composition and performance.
Catalysis
Toshiaki Funako; Patchanee Chammingkwan; Toshiaki Taniike; Minoru Terano
Abstract
In Ziegler-Natta olefin polymerization, the pore architecture of catalysts plays a crucial role in catalytic performances and polymer properties. While the type of preparation routes (such as chemical reaction and solution precipitation) greatly affects the catalyst pore architecture as a result of different ...
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In Ziegler-Natta olefin polymerization, the pore architecture of catalysts plays a crucial role in catalytic performances and polymer properties. While the type of preparation routes (such as chemical reaction and solution precipitation) greatly affects the catalyst pore architecture as a result of different solidification mechanisms, the modification of the pore architecture within a given route has been hardly achieved. In this study, we propose a simple way to vary the pore architecture of Mg(OEt)2-based Ziegler-Natta catalysts by the addition of a second alcohol. It was found that the addition of a second alcohol during Mg(OEt)2 synthesis affected not only the morphology of Mg(OEt)2 macroparticles but also the shape of building units. The degree of alternation was found to be sensitive to the molecular structure of a second alcohol. Noticeable influences were observed in the case of branched alcohols, where the transformation of plate-like building units to cylindrical ones led to the generation of totally different pore size distributions of resultant catalysts.
Catalysis
Toshiaki Taniike; Keisuke Goto; Minoru Terano
Abstract
Heterogeneous Ziegler-Natta and homogeneous metallocene catalysts exhibit greatly different active sitenature in olefin polymerization. In our previous study, it was reported that MgCl2-supported titanocenecatalysts can generate both Ziegler-Natta-type and metallocene-type active sites according to the ...
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Heterogeneous Ziegler-Natta and homogeneous metallocene catalysts exhibit greatly different active sitenature in olefin polymerization. In our previous study, it was reported that MgCl2-supported titanocenecatalysts can generate both Ziegler-Natta-type and metallocene-type active sites according to the type of activators.The dual active site nature of the supported titanocene catalysts was further explored in the present study: The influence of the ligand structure of titanocene precursors was studied on the nature of active sites when supported on MgCl2 in ethylene and propylene homopolymerization, and ethylene/1-hexene copolymerization. It was found that the reducibility of titanocene precursors by alkylaluminum is closely related to the appearance of the dual active site nature, while the kind of olefin did not affect the type of active sites formed during polymerization. The Ziegler-Natta-type active sites produced poorly isotactic polypropylene and less branched polyethylene, while the metallocene-type active sites produced atactic polypropylene and exhibited much higher incorporation efficiency for 1-hexene.
Characterization
Ning Zhao; Ruihua Cheng; Qi Dong; Xuelian He; Zhen Liu; Shiliang Zhang; Minoru Terano; Boping Liu
Abstract
SiO2-supported silyl chromate catalyst is an important industrial catalyst for production of high grade HDPE pipe materials. The control of the short chain branch (SCB) distribution using this catalyst system is still a great challenge. In this work, ethylene and 1-hexene copolymers were synthesized ...
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SiO2-supported silyl chromate catalyst is an important industrial catalyst for production of high grade HDPE pipe materials. The control of the short chain branch (SCB) distribution using this catalyst system is still a great challenge. In this work, ethylene and 1-hexene copolymers were synthesized using SiO2-supported silyl chromate catalyst combined with triisobutylaluminium (TIBA), triethylaluminium (TEA) and mixed TIBA/TEA at molar ratio 1:1 (TIBA/TEA/1:1) as three different Al-alkyl co-catalysts.The temperature rising elution fractionation (TREF) and successive self-nucleation and annealing (SSA, by DSC) methods were combined to analyze the short chain branch distribution (SCBD) of these ethylene/1-hexene copolymers. The results showed that different types of co-catalyst had a great influence on SCBD of ethylene/1-hexene copolymers. The copolymer produced with TIBA showed better SCBD than the copolymer produced with TEA, and the copolymer produced with TIBA/ TEA/1:1 showed a SCBD in between those with TIBA and TEA.
