Titanium distribution on the surface of Ziegler-Natta catalysts observed by scanning Auger electron microscopy

Hasebe, Koichi; Mori, Hideharu; Tomitori, Masahiko; Keii, Tominaga; Terano, Minoru

doi:10.1016/s1381-1169(96)00339-1

Cited by 12 publications

(3 citation statements)

References 9 publications

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“…First, the titanium species are not expected to have longrange order on the supported catalyst that is necessary for diffraction. 12 Second, the primary electron beam of LEED will alter the film composition via electronstimulated desorption (ESD) of chlorine. 10 The Ti-Cl bond of a TiCl x species would be more susceptible to electroninduced dissociation than the Mg-Cl bond of the MgCl 2 substrate.…”

Section: Introductionmentioning

confidence: 99%

“…However, LEED would not be an appropriate technique for a titanium chloride film supported on MgCl 2 (TiCl x /MgCl 2 ). First, the titanium species are not expected to have long-range order on the supported catalyst that is necessary for diffraction . Second, the primary electron beam of LEED will alter the film composition via electron-stimulated desorption (ESD) of chlorine .…”

Section: Introductionmentioning

confidence: 99%

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Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

2000

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Temperature-programmed desorption (TPD) of physisorbed mesitylene molecules has been used as a nondestructive surface probe to distinguish the surface adsorption sites of model Ziegler-Natta polymerization catalysts. A MgCl2-supported titanium chloride film (TiClx/MgCl2) was fabricated on an inert gold substrate by codeposition of Mg metal and TiCl4 from the gas phase. The mesitylene TPD probe revealed two types of surface adsorption sites. The dominant site was attributed to the basal plane of these halide crystallites. The minor site could be tentatively attributed to a defective structure at the basal plane boundaries or other crystal planes. Due to the chlorine termination nature of the catalyst surface, the metal ions under the chlorine layer could not be differentiated directly with the physisorbed mesitylene molecules. However, the mesitylene TPD profile was able to monitor compositional changes in the outermost chlorine layer accompanying the reaction of the catalyst film with the triethylaluminum cocatalyst, electron beam irradiation of the film surface, and diffusion of bulk chlorine to minimize the number of defect sites.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

2000

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“…These modern high-performance surface analytical techniques are thought to give a possibility to allow direct observation of the active species on Ziegler-Natta catalysts. On the basis of this consideration, in our previous studies, the characterization of the various Ziegler-Natta catalysts has been conducted by several methods, such as FT-IR and thermal analysis, [6][7] solid-state 13 C-NMR, [8] scanning Auger electron microscopy, [9][10] X-ray photoelectron spectroscopy, [11][12][13] Raman spectroscopy, [14] and high resolution transmission electron microscopy (HRTEM). [15] Among them, HRTEM is one of the most powerful tools Full Paper: High resolution transmission electron microscopy (HRTEM) was used to directly observe the distribution of crystalline regions in Ziegler catalysts prepared by mechanical plus chemical routes (internal donor; Cat-A: ethylbenzoate, Cat-B: dibutylphthalate, Cat-C: none) and by an entirely chemical route (internal donor; Cat-D: dibutylphthalate).…”

Section: Introductionmentioning

confidence: 99%

High resolution transmission electron microscope observation of industrial high performance Ziegler catalysts

Mori

Higuchi

Ōtsuka³

et al. 2000

Macromol. Chem. Phys.

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High resolution transmission electron microscopy (HRTEM) was used to directly observe the distribution of crystalline regions in Ziegler catalysts prepared by mechanical plus chemical routes (internal donor; Cat‐A: ethylbenzoate, Cat‐B: dibutylphthalate, Cat‐C: none) and by an entirely chemical route (internal donor; Cat‐D: dibutylphthalate). A comparison of Cat‐A, Cat‐B, and their precursors (ground products of an original MgCl2 with a donor) indicates that MgCl2 crystals are significantly destroyed by the co‐grinding procedure regardless of the kinds of internal donor, and further destruction preferentially occurs in Cat‐B compared with that in Cat‐A. The crystalline lattice of the original MgCl2 is destroyed from the surface into the interior region in the catalysts prepared by the former method. The destruction of the crystals is found to be severe in the following order: Cat‐C ≥ Cat‐B > Cat‐A in the surface area, Cat‐C > Cat‐B > Cat‐A in the central area. On the other hand, Cat‐D shows the different distribution of crystalline regions, which are predominantly present in the near‐surface area, but absent in the central area. These results suggest that the distribution of MgCl2 crystalline regions exhibit a strong correlation with the catalyst preparation procedures and, hence, the catalyst performance.

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Biphasic Catalysis—Homogeneous

Joó

2010

Encyclopedia of Catalysis

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Homogeneous catalysis offers advantages over heterogeneous catalytic methods in that all catalyst molecules are available for the substrate, and the catalyst can be tailored to the desired chemical transformation by choosing (designing) the proper ligand environment. In most cases, however, industry uses heterogeneous catalysts because (in addition to their high activity and selectivity) catalyst–product separation poses no serious problems. A successful way of heterogenization of homogeneous catalysts is the separation of the reactants (products) and the catalyst into immiscible liquid phases (liquid multiphase catalysis). This article reviews biphasic catalysis with homogeneously (molecularly) dispersed catalysts. Attention is focused on liquid–liquid biphasic systems, containing all the reactants and the catalyst(s) in dissolved state. Such biphasic systems are built up of two or more solvents with limited mutual solubility. Aqueous–organic and organic–organic (including also fluorous ) biphasic systems have been studied for long; however, the use of biphasic reaction mixtures designed by using fluorous solvents , ionic liquids , and supercritical gases in combination with each other or with appropriate aqueous or organic solvents has been rapidly developing recently. The properties of such systems together with the need of special ligand design or modifications are discussed, and their use is illustrated by describing typical reactions (hydrogenation, hydrogen transfer, hydroformylation, hydrocarboxylation, carbonylation, alkene metathesis, dimerization, polymerization, and other CC coupling reactions).

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Titanium distribution on the surface of Ziegler-Natta catalysts observed by scanning Auger electron microscopy

Cited by 12 publications

References 9 publications

Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

High resolution transmission electron microscope observation of industrial high performance Ziegler catalysts

Biphasic Catalysis—Homogeneous

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Titanium distribution on the surface of Ziegler-Natta catalysts observed by scanning Auger electron microscopy

Cited by 12 publications

References 9 publications

Surface Characterization of the TiClx/MgCl2 Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

Surface Characterization of the TiClx/MgCl2 Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

High resolution transmission electron microscope observation of industrial high performance Ziegler catalysts

Biphasic Catalysis—Homogeneous

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Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption

Surface Characterization of the TiCl_x/MgCl₂ Model Ziegler−Natta Polymerization Catalysts: Adsorption Site Studies Using Mesitylene Thermal Desorption