Mechanism of Formation of a Catalytically Active Phase in the Reaction of CrO2Cl2 with Silica Gel

Mehandjiev, D.; Angelov, S.; Damyanov, D.

doi:10.1016/s0167-2991(09)60238-x

Cited by 6 publications

(16 citation statements)

References 3 publications

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“…Resolution of these mechanistic scenarios would be aided by a model system containing a high number of active sites, which could be studied in more detail. Immobilization of CrO 2 Cl 2 or related chromates on silica was investigated to obtain well‐defined Cr VI ‐dioxo surface species . On contact with ethylene, the Cr VI ‐containing materials form active species and show behavior similar to that of the Phillips catalyst …”

Section: Alkene Polymerizationsupporting

confidence: 68%

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Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

et al. 2018

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Many industrial catalysts contain isolated metal sites on the surface of oxide supports. Although such catalysts have been used in a broad range of processes for more than 40 years, there is often a very limited understanding about the structure of the catalytically active sites. This Review discusses how surface organometallic chemistry (SOMC) engineers surface sites with well-defined structures and provides insight into the nature of the active sites of industrial catalysts; the Review focuses in particular on olefin production and conversion processes.

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Section: Alkene Polymerizationsupporting

confidence: 68%

“…[287][288][289][290][291][292] On contact with ethylene, the Cr VI -containing materials form active species and show behavior similar to that of the Phillips catalyst. Immobilization of CrO 2 Cl 2 or related chromates on silica was investigated to obtain well-defined Cr VI -dioxo surface species.…”

Section: Chain Growth In the Phillips Catalystmentioning

confidence: 96%

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

et al. 2018

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“…Die Überprüfung dieser mechanistischen Szenarien würde durch ein Modellsystem mit zahlreichen aktiven Zentren erleichtert, die ausführlicher untersucht werden können. Durch verankern von CrO 2 Cl 2 oder verwandten Chromaten auf Siliciumdioxid wurden gut definierte Cr VI ‐Dioxo‐Oberflächenspezies . Bei Kontakt mit Ethylen bilden die Cr VI ‐haltigen Materialien aktive Spezies und verhalten sich ähnlich wie der Phillips‐Katalysator …”

Section: Alkenpolymerisationunclassified

Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

et al. 2018

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Viele industrielle Katalysatoren enthalten isolierte Metallzentren an der Oberfläche von Oxidträgern. Derartige Katalysatoren werden seit über 40 Jahren bei verschiedensten Verfahren verwendet – die Struktur ihrer katalytischen Zentren bleibt aber bis heute nur ungenügend verstanden. Dieser Aufsatz zeigt, wie mit metallorganischer Oberflächenchemie (SOMC) Oberflächenzentren mit gut definierten Strukturen erzeugt werden können, und beschreibt die Beschaffenheit aktiver Zentren in industriellen Katalysatoren, insbesondere für die Herstellung und Umwandlung von Olefinen.

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“…Surface chemistry was then studied using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), static secondary ion mass spectrometry (SSIMS), work function change measurement (ΔΦ), and X-ray photoelectron spectroscopy (XPS). To the authors' knowledge, no information regarding the interactions of Cr(VI)-containing inorganic molecules such as chromyl chloride with polycrystalline or single-crystal TiO 2 is available in the published literature, although there are published accounts dealing with chromyl chloride adsorption on other oxide materials. − This paper deals with the thermal induced chemistry of chromyl chloride at the TiO 2 (110) surface in the absence of coadsorbed water. More specifically, the objectives of the study are to understand the binding of chromyl chloride with the TiO 2 (110) surface, to quantify the partitioning between the desorbed and the decomposed chromyl chloride, and to determine the chromyl chloride decomposition pathways.…”

Section: Introductionmentioning

confidence: 99%

Chromyl Chloride Chemistry on the TiO₂(110) Surface

et al. 1998

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The surface chemistry of chromyl chloride (CrO2Cl2) on TiO2(110) was examined with TPD, AES, ΔΦ measurements, SSIMS, and XPS. CrO2Cl2 adsorbs on TiO2(110) at 130 K with a constant, coverage-independent sticking probability, which is presumably near unity based on TPD. ΔΦ data suggest the molecule is adsorbed with the oxygens bound to the surface and the chlorines pointing into vacuum. In TPD, multilayer CrO2Cl2 desorption occurs at 156 K, and monolayer desorption states occur at about 295 and 430 K. Approximately 0.09 ML (1 ML = 5.2 × 1014 sites/cm2) desorbs in each of the latter states. The remaining adsorbed CrO2Cl2 (0.48 ML) decomposes irreversibly above 500 K, eventually resulting in CrCl2 desorption above 700 K. No other decomposition products are observed in TPD. Adsorption of CrO2Cl2 at 585 K results in multilayer CrCl2 formation, while adsorption at or below 500 K results in a saturated monolayer. Between 500 and 700 K, XPS results suggest that the Cr deposited from CrO2Cl2 decomposition is reduced, possibly as the result of charge transfer from the defects in the n-doped TiO2(110). SSIMS experiments conducted on the 18O-enriched TiO2(110) indicate that 16O brought in by CrO2Cl2 is incorporated into the surface, whereas TPD indicates that only a small fraction of this incorporated 16O is due to isotopic exchange into the desorbing parent at 400 K. Since no oxygen-containing decomposition products were observed in TPD, the decomposition of CrO2Cl2 on TiO2(110) involves reaction at reduced surface sites (oxygen vacancies). As evidence for this, SSIMS indicates that the reaction of 18O2 with Ti16O2(110) resulting in 18O incorporation proceeds above 520 K presumably by the formation of oxygen vacancies from 16O2 desorption. These results suggest that the reduction and potential immobilization of Cr(VI) species on TiO2 materials may occur thermally if the appropriate surface defect sites are present.

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Mechanism of Formation of a Catalytically Active Phase in the Reaction of CrO2Cl2 with Silica Gel

Cited by 6 publications

References 3 publications

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

Chromyl Chloride Chemistry on the TiO₂(110) Surface

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Mechanism of Formation of a Catalytically Active Phase in the Reaction of CrO2Cl2 with Silica Gel

Cited by 6 publications

References 3 publications

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

Chromyl Chloride Chemistry on the TiO2(110) Surface

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Product

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Chromyl Chloride Chemistry on the TiO₂(110) Surface