Investigation of the physico-chemical state and aggregation mechanism of surface Cr species on a Phillips CrOx/SiO2 catalyst by XPS and EPMA

Liu, Boping; Terano, Minoru

doi:10.1016/s1381-1169(01)00121-2

Cited by 91 publications

(84 citation statements)

References 52 publications

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“…An investigation on the oxidation states of Cr ions in/on catalysts is beneficial for the elucidation of the nature of the active sites. According to what have been reported in the literature [26][27][28][29], the Binding Energy (BE) of Cr2p 3/2 signals at ca. 577 eV could be assigned to Cr 3+ ions whereas those at ca.…”

Section: Textural Properties Of Catalystsmentioning

confidence: 57%

Oxidative Dehydrogenation of Ethane to Ethylene with Carbon dioxide over Cr–Ce/SBA-15 Catalysts

Shi

Wang

2008

Catal Lett

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Chromium oxide supported on SBA-15 was modified with Ce species by an incipient method. The effect of Ce on the activity of Cr/SBA-15 catalyst in the dehydrogenation of ethane with CO 2 was investigated. The activity is enhanced for Ce modified Cr/SBA-15 catalyst for the dehydrogenation of ethane with CO 2 . The cycle between Cr 6+ and Cr 3+ species can be carried out viaing the dehydrogenation of ethane and oxidation of CO 2 processes.

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Section: Textural Properties Of Catalystsmentioning

confidence: 57%

Oxidative Dehydrogenation of Ethane to Ethylene with Carbon dioxide over Cr–Ce/SBA-15 Catalysts

Shi

Wang

2008

Catal Lett

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“…The presence of CrO 3 has also been observed in literature for temperatures less than and greater than the estimated temperature range in this study (100-230 • C). 27,31,44 The stability of CrO 3 is temperature dependent, however, and can give rise to other compounds beginning at temperatures as low as 200 • C. 31 Theories regarding the formation of these compounds are also available from literature. Formation of chromate (M-CrO 4 ) is believed to be caused by an esterification reaction between CrO 3 and surface hydroxyl groups which may occur near 200 • C, and subsequently stabilize the hexavalent form for temperatures exceeding 1000 • C. 24,31,46,47 Dichromate (M-Cr 2 O 7 ) is believed to form from anchored chromate as chromium loading increases on the sample surface.…”

Section: Resultsmentioning

confidence: 99%

“…28 As chromium loading increases, hydroxyl groups diminish and chromate species may form O-Cr-O bonds resulting in polychromated species, and eventually CrO 3 . 44,51 The agglomerated chromate species are minimally anchored to the surface and therefore are minimally stabilized. At this stage the color would appear to be brown (Figures 4a, 5, and 9).…”

Section: Resultsmentioning

confidence: 99%

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XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

Tatar¹,

Gannon²,

Swain³

et al. 2018

J. Electrochem. Soc.

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Chromium containing materials, e.g. stainless steels, are commonly used in high temperature (>500 • C) applications such as solid oxide fuel cell (SOFC) stacks, combustion exhaust systems, and in various chemical process equipment. At these temperatures and in oxidizing atmospheres, chromium oxide (chromia) surface layers form and grow, effectively protecting the underlying alloy. Also known to form under these conditions, however, are volatile chromium species such as CrO 2 (OH) 2 and CrO 3 . Formation of these volatile species may have detrimental effects not only on the source material, but also on surrounding materials in the system which may interact with these species. To better understand how volatile chromium species interact with materials, volatile chromium species were generated from ferritic stainless steel (FSS) T409 at 700 • C and directed into aluminosilicate fibers at 100-230 • C for 150 hours. Post exposure fibers were noted to possess yellow, brown, and/or green stained regions which were isolated and characterized using X-ray photoelectron spectroscopy (XPS). Examination of Cr 2p 3/2 peaks revealed varied Cr(VI) content and Cr(III) multiplet-split components for different discolored regions. Possible explanations for differences in chromium content by discoloration color are discussed. The volatilization of chromium species from chromium containing materials is a well-documented phenomenon which holds consequences for SOFCs, human health, and the environment. Using chromia as an example for a source, in the presence of oxygen and absence of water vapor, the dominant volatilization pathway proceeds according to Reaction 1.If, however, water vapor is present in addition to oxygen, then the dominant volatilization pathway proceeds according to Reaction 2. 1-7The generation of these gas/vapor species is well understood, but the same cannot be said of how they interact with (e.g. condense onto) other materials. This is of great importance for human health and the environment considering that chromium species may take toxic forms (hexavalent) or non-toxic forms (trivalent). This relative dearth of understanding also holds negative implications for SOFCs, and so many investigative efforts have been undertaken to understand how CrO 2 (OH) 2 interacts with ceramic components in SOFCs. Electrochemical reduction of CrO 2 (OH) 2 has often been observed to occur at the triple phase boundary (TPB), where cathode, electrolyte, and gas phase meet. [8][9][10] This electrochemical reaction is not limited to the TPB, however, and can occur away from the TPB given: the formation of a continuous chromia layer for hole transport, a mixed conducting electrolyte, or a mixed conducting cathode. 8 While there is evidence for preferential electrochemical reduction of CrO 2 (OH) 2 , 11,12 open circuit chemical reactions have also been observed with cathodes containing Mn or Sr. 13 It should be noted that Cr transport to lanthanum strontium manganite (LSM) was observed via solid state diffusion, whereas vapor deposition o...

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“…Many researches reported that, the BE of 576.3-576.9 eV [15][16][17][18][19][20] is a characteristic for Cr 3+ , and the supported Cr 3+ has a higher BE than the bulk chromium (III) oxide. Therefore, the peak at 576.4 eV can be assigned to Cr 3+ .The peak at 577.6 eV may be assigned to the mixed valence of Cr 3+ and Cr 4+ [18] or the valence of Cr 3+ in Cr(OH) 3 [19] .…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of ultra-fine Cr2O3 from hydrogen reduction of K2CrO4

Bai

Zhang

et al. 2008

J. Wuhan Univ. Technol.-Mat. Sci. Edit.

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As a part of the green process for manufacturing chromium compounds, two steps are involved in the synthesis of ultra-fine Cr 2 O 3 powders: the first is the hydrogen reduction of K 2 CrO 4 into intermediate trivalent (Cr 3+ ) or tetravalent (Cr 4+ ) chromium compounds; the second is the decomposing of the intermediate into Cr 2 O 3 by heat treating. The intermediate is well characterized by means of SEM, XRD, and XPS. The possible reaction mechanism of the process is analyzed.

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Investigation of the physico-chemical state and aggregation mechanism of surface Cr species on a Phillips CrOx/SiO2 catalyst by XPS and EPMA

Cited by 91 publications

References 52 publications

Oxidative Dehydrogenation of Ethane to Ethylene with Carbon dioxide over Cr–Ce/SBA-15 Catalysts

Oxidative Dehydrogenation of Ethane to Ethylene with Carbon dioxide over Cr–Ce/SBA-15 Catalysts

XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

Synthesis and characterization of ultra-fine Cr2O3 from hydrogen reduction of K2CrO4

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