Characterization of chromia/alumina catalysts by X-ray photoelectron spectroscopy, proton induced X-ray emission and thermogravimetric analysis

Rahman, Ataur; Mohamed, Mohamed A.; Ahmed, Moataz; Aitani, A.

doi:10.1016/0926-860x(94)00204-5

Cited by 85 publications

(35 citation statements)

References 22 publications

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“…A peak position of 576-576.3 eV (as is observed in the spectra) is well supported in literature for chromia. 25,41,42 This assignment will be discussed in further detail below.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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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“…A peak position of 576-576.3 eV (as is observed in the spectra) is well supported in literature for chromia. 25,41,42 This assignment will be discussed in further detail below.…”

Section: Resultsmentioning

confidence: 99%

“…The observed range is well supported in literature for chromia. 25,41,42 Determining 37 and as tetrahedral Cr 6+ and octahedral Cr 3+ linkages. 33,36 Claims have also been made that Cr 2 O 5 is a single valence Cr 5+ species.…”

Section: Resultsmentioning

confidence: 99%

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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“…The initial mass-loss steps (I&II; total observed mass loss ≈ 70%) are notably steepened (kinetically enhanced) and completed near 473 K (instead of 573 K for Cr(NF)). The corresponding DTA curve reveals that this mass loss process is preceded by two mass-invariant endothermic processes at 390 and 443 K, and succeeded by a mass-invariant exothermic process at 483 K. A previous study [19] disclosed that following the phase-transition marked by the weak endotherm at 390 K [27] and the melting of the included NH 4 NO 3 (the subsequent weak endotherm at 443 K) [28] a solid state reaction was involved leading to the formation of (NH 4 ) 2 Cr 2 O 7 -like phase, whose reductive decomposition into ␣-Cr 2 O 3 was considered responsible for the exotherm at 483 K [29]. The minute mass loss (≈2%) near 683 K (IV), and the corresponding sharp, but small, exotherm at 683 K (IV) are indicative of the calcination course of domains of the gel that had not been involved in interactions with the nitrate contaminant.…”

Section: The Course Of Thermal Genesis Of the Calcined Chromiamentioning

confidence: 92%

“…On the other hand, the sharp exotherm at 683 K (IV) is due to release of excess oxygen and an immediate crystallisation of the product into an ␣-Cr 2 O 3 phase [25]. When analysed using X-ray diffraction [19,21], X-ray photoelectron spectroscopy [26,27] and other chemical and physicochemical means [3,4,7,8], the intermediate ␥-Cr 2 O 3+x phase has been found to assume a noncrystalline bulk structure with a chromium chromate-like composition, whereas the final ␣-Cr 2 O 3 product occurs as microcrystallites embedded in noncrystalline chromia exposing chromate-covered surfaces. The surface chromate species were partially stable to calcination at 873 K [26,27].…”

Section: The Course Of Thermal Genesis Of the Calcined Chromiamentioning

confidence: 99%

Low-temperature adsorption of oxygen on calcined chromia: IR spectroscopic and sorptiometric evidence for oxygen-assisted topochemical reduction of surface chromate species

Fahim

Zaki

Fouad

et al. 2004

Applied Catalysis A: General

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“…Chromia catalysts have been subject to extensive characterisation using a variety of techniques such as electron spin resonance (ESR) [40,41], infrared spectroscopy (IR) [42,43], diffuse reflectance spectroscopy (DRS) [44,45], photon electron spectroscopy (XPS) [46,47], X-ray diffraction (XRD) [48][49][50], thermo-gravimetric analysis (TGA) [49,50] and Raman spectroscopy [51,52]. Although in the as-prepared catalyst chromia is often in a 6?…”

Section: Catalytic Processes For Trans-hydrogenationmentioning

confidence: 99%

Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

Garba

Jackson

2016

Appl Petrochem Res

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The production of high premium fuel is an issue of priority to every refinery. The trans-hydrogenation process is devised to convert two low valued refinery cracked products to premium products; the conversion processes involve the combination of dehydrogenation and hydrogenation reaction as a single step process. The paper reviews the recent literature on the use of catalysts to convert low value refinery products (i.e. alkanes and alkynes or alkadienes) to alkenes (olefins) by trans-hydrogenation. Catalysts based on VO x , CrO x and Pt all supported on alumina have been used for the process. However, further studies are still required to ascertain the actual reaction mechanism, mitigating carbon deposition and catalyst deactivation, and the role of different catalysts to optimize the reaction desired products.

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Characterization of chromia/alumina catalysts by X-ray photoelectron spectroscopy, proton induced X-ray emission and thermogravimetric analysis

Cited by 85 publications

References 22 publications

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

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

Low-temperature adsorption of oxygen on calcined chromia: IR spectroscopic and sorptiometric evidence for oxygen-assisted topochemical reduction of surface chromate species

Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

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