Characterization of the coke formed on reforming catalysts by laser raman spectroscopy

Espinat, D.; De×pert, H.; Freund, E.; Martino, G.; Couzi, M.; Lespade, P.; Cruège, F.

doi:10.1016/s0166-9834(00)84398-5

Cited by 77 publications

(45 citation statements)

References 13 publications

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“…Raman spectrometry have been widely applied to the study of used catalysts (for instance, see [20][21][22]). Two linked phenomena are responsible for the catalyst deactivation: the structural evolution of the active phase and the deposit of carbonaceous compounds on the catalyst surface.…”

Section: Used Catalysts Characterizationmentioning

confidence: 99%

“…Moreover, the size of coke clusters can modify the relative intensities of Raman band: for graphite, the intensity ratio I 1355 /I 1585 increases when the graphite particle size decreases. Such a correlation is assumed to be true for coke on catalyst [20]. Beyond these qualitative aspects, Raman spectrometry have been recently proposed as a quantitative method to measure the amount of coke, during the dehydrogenation of propane on Cr/Al 2 O 3 [25].…”

Section: Used Catalysts Characterizationmentioning

confidence: 99%

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Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry

Digne¹,

Marchand²,

Bourges³

2007

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Suivi de la synthèse et de la désactivation des catalyseurs d'hydrotraitement par spectrométrie Raman -La spectrométrie Raman est devenue une technique de caractérisation populaire pour les catalyseurs d'hydrotraitement : elle fournit des informations importantes sur la structure chimique, au cours du cycle de synthèse du catalyseur. Les phénomènes physico-chimiques se déroulant sur la surface du catalyseur peuvent être suivis par cette technique. Cet article décrit quelques exemples où la spectrométrie Raman a permis d'évaluer l'impact de paramètres expérimentaux (choix de précur-seurs métalliques, présence d'impureté, influence de la température de calcination, dépôt de coke) sur la structure du catalyseur. Abstract -Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry -Raman spectrometry has become a popular characterization technique for hydrotreatment catalysts: it provides important information on chemical structures along all the synthesis cycle

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Section: Used Catalysts Characterizationmentioning

confidence: 99%

Section: Used Catalysts Characterizationmentioning

confidence: 99%

Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry

Digne¹,

Marchand²,

Bourges³

2007

Oil & Gas Science and Technology - Rev. IFP

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show abstract

“…24 -26,36 -40 These bands have been assigned to C C stretching vibrations of unsaturated hydrocarbons, namely olefins, 36,37 polyolefins, 36 aromatic compounds, polyaromatic compounds or pregraphitic coke species. 24,26,38 Additional bands in the range between 1380 and 1340 cm 1 are frequently reported and are assigned to C-H deformation bands and/or to defects in pregraphitic or graphitic particles. 38,41 The Raman spectra of these different organic species are very similar and can only be discriminated by small differences of the Raman wavenumbers.…”

Section: Coke Formation On a Wo 3 /Zro 2 Catalystmentioning

confidence: 99%

Time‐resolved in situ Raman spectroscopy of working catalysts: sulfated and tungstated zirconia

Kuba

Knözinger

2002

J Raman Spectroscopy

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The spectra of time-dependent in situ Raman experiments on sulfated and tungstated zirconia catalysts during the isomerization reaction of n-pentane are presented and discussed. A purpose-made in situ Raman cell which was used for this application is described. The choice of appropriate experimental parameters, namely laser power and laser wavelength, is discussed. During the experiments the activity and selectivity of the catalysts were determined simultaneously by on-line gas chromatography. The sulfated zirconia catalyst shows structural changes in the sulfate region during the reaction. One of two different types of initially present sulfate species is eroded during the reaction, presumably due to a reduction to H 2 S. The activity shows a typical induction period followed by a fast deactivation. No coke formation is observed. Since fast deactivation occurs, coke formation cannot be the only reason for the deactivation of the catalyst. The tungstated catalyst shows strong darkening after initiation of the reaction with increasing time-on-stream (TOS). This leads to the disappearance of the catalyst bands. However, coke formation indicated by a broad band at 1590 cm −1 can be observed. Since darkening has a strong effect on Raman intensities, the time evolution of the observed bands is not obtained correctly. We propose a new method to correct for the effect of the darkening. The change of the diffuse reflectance of the catalyst is determined by the variation of the intensity of laser plasma lines. Based on an approximate equation proposed by Waters which correlates the Raman intensities and the diffuse reflectance of a sample, a correction factor for the spectra is obtained. After the intensity correction the spectra indicate that most of the coke is formed in the first few minutes of the reaction followed by a constant formation rate with TOS.

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“…The deconvolution additionally revealed a very broad background contribution to this band from CÀH, CÀC deformations. [12] This very broad D band does not exclude the presence of sp 3 -hybridized carbon atoms after the reaction, as indicated by XRD (Figure 2 B, pattern b). [12] Indeed, IR spectroscopy (spectra not shown) revealed the presence of CÀH valence bands at 2920 cm À1 after catalysis, together with bands at 1740, 1175, and 1090 cm À1 which indicate the presence of basic CO and CÀO groups, respectively.…”

mentioning

confidence: 91%

The Catalytic Use of Onion-Like Carbon Materials for Styrene Synthesis by Oxidative Dehydrogenation of Ethylbenzene

Keller

Maksimova

Roddatis

et al. 2002

Angew. Chem. Int. Ed.

262

141

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Characterization of the coke formed on reforming catalysts by laser raman spectroscopy

Cited by 77 publications

References 13 publications

Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry

Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry

Time‐resolved in situ Raman spectroscopy of working catalysts: sulfated and tungstated zirconia

The Catalytic Use of Onion-Like Carbon Materials for Styrene Synthesis by Oxidative Dehydrogenation of Ethylbenzene

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