Comparative Study of Distribution of Active Sites According to Their Stereospecificity in Propylene Polymerization over the Traditional TiCl3 and Supported Titanium-Magnesium Catalysts with Different Composition

2018 ◽  
Vol 219 (5) ◽  
pp. 1700488 ◽  
Author(s):  
Marina Nikolaeva ◽  
Mikhail Matsko ◽  
Vladimir Zakharov
Keyword(s):  
Comparative Study ◽  
Active Sites ◽  
Propylene Polymerization

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 Comparative study of the active sites in zeolites by different probe molecules

2005 ◽  
Vol 70 (3) ◽  
pp. 457-474 ◽  
Author(s):  
Vera Dondur ◽  
Vesna Rakic ◽  
Ljiljana Damjanovic ◽  
Aline Auroux
Keyword(s):  
Comparative Study ◽  
Active Sites ◽  
Temperature Programmed Desorption ◽  
Acid Sites ◽  
Probe Molecules ◽  
Adsorption Calorimetry ◽  
Temperature Programmed ◽  
First Time

This review summarizes some of the recently published results concerning the acid sites in the zeolites ZSM-5 and Y studied by temperature-programmed desorption (TPD) and adsorption calorimetry using different probe molecules NH3, CO, N2O and n-hexane. For the first time it has been shown that the acid sites in hydrated zeolites are accessible for n-hexane adsorption.

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.

scholarly journals Comparative Study of the Efficiency of Different Noble Metals Supported on Hydroxyapatite in the Catalytic Lean Methane Oxidation under Realistic Conditions

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3612
Author(s):  
Zouhair Boukha ◽  
Beatriz de Rivas ◽  
Juan R. González-Velasco ◽  
José I. Gutiérrez-Ortiz ◽  
Rubén López-Fonseca
Keyword(s):  
Comparative Study ◽  
Active Sites ◽  
Noble Metals ◽  
Nir Spectroscopy ◽  
Catalytic Performance ◽  
Ruthenium Catalysts ◽  
Slow Process ◽  
Inhibiting Effect ◽  
Degree Of Oxidation ◽  
Negative Effect

The combustion of lean methane was studied over palladium, rhodium, platinum, and ruthenium catalysts supported on hydroxyapatite (HAP). The samples were prepared by wetness impregnation and thoroughly characterized by BET, XRD, UV-Vis-NIR spectroscopy, H2-TPR, OSC, CO chemisorption, and TEM techniques. It was found that the Pd/HAP and Rh/HAP catalysts exhibited a higher activity compared with Pt/HAP and Ru/HAP samples. Thus, the degree of oxidation of the supported metal under the reaction mixture notably influenced its catalytic performance. Although Pd and Rh catalysts could be easily re-oxidized, the re-oxidation of Pt and Ru samples appeared to be a slow process, resulting in small amounts of metal oxide active sites. Feeding water and CO2 was found to have a negative effect, which was more pronounced in the presence of water, on the activity of Pd and Rh catalysts. However, the inhibiting effect of CO2 and H2O decreased by increasing the reaction temperature.

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