Initial Activity of Reduced Chromia/Alumina Catalyst inn-Butane Dehydrogenation Monitored by On-Line FT–IR Gas Analysis

Hakuli, A.; Kytökivi, Arla; Krause, A.O.I.; Suntola, Tuomo

doi:10.1006/jcat.1996.0197

Cited by 77 publications

(77 citation statements)

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“…A common feature of all the spectra measured at the end of oxidation was that there was an absorption band centered at 25,000-26,000 cm −1 , which was due to Cr 6+ (22). The Cr 6+ present in the fresh catalyst was readily reduced to Cr 3+ during the first 30 s of propane on stream, in accord with the observations of Hakuli et al (20) which were made by a rapid Fourier transfer infrared analysis of the gas phase products. For the deactivated catalyst in all cycles and for the fresh catalysts in the second and third cycles, Cr 6+ was not stable during the helium flush but converted to Cr 3+ .…”

Section: Figsupporting

confidence: 77%

“…2. The data points (17.1 min on stream) represent a "stable" situation of the catalysts, where all the Cr 6+ has been converted to Cr 3+ and the initial CO 2 , CO, and H 2 O formation (20) no longer affects the product distribution. Increasing the alumina pretreatment temperature had a positive effect on the dehydrogenation activity of the catalysts.…”

Section: Resultsmentioning

confidence: 99%

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Monitoring Chromia/Alumina Catalysts in Situ during Propane Dehydrogenation by Optical Fiber UV–Visible Diffuse Reflectance Spectroscopy

Puurunen

Beheydt

Weckhuysen

2001

Journal of Catalysis

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A continuous-flow reactor system with in situ monitoring of the catalyst was developed. The catalyst surface was analyzed by collecting UV-visible diffuse reflectance spectra through an optical fiber placed in the catalyst bed. The system was tested with a series of chromia/alumina catalysts (1 wt% Cr) under the conditions of propane dehydrogenation. The fast reduction of Cr 6+ to Cr 3+ under propane stream could be detected. Increase in the catalytic activity with the alumina pretreatment temperature was tentatively ascribed to the presence of θ-alumina, and decrease in the activity during calcination to incorporation of Cr 3+ inside the alumina support.

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Section: Figsupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Monitoring Chromia/Alumina Catalysts in Situ during Propane Dehydrogenation by Optical Fiber UV–Visible Diffuse Reflectance Spectroscopy

Puurunen

Beheydt

Weckhuysen

2001

Journal of Catalysis

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“…, as also evidenced by the UV-Vis DRS studies. Sulfate ion addition helps promote chromium with higher oxidation states [33]. Since XPS is a surface technique, it is not possible to estimate the overall quantity of Cr 6?…”

Section: O1s Xpsmentioning

confidence: 99%

Oxidative dehydrogenation of ethane with carbon dioxide over Cr2O3/SBA-15 catalysts: the influence of sulfate modification of the support

et al. 2017

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Unmodified and sulfate-modified SBA-15-supported Cr 2 O 3 catalysts were prepared by impregnation method. The physico-chemical properties of the supports and catalysts were determined by nitrogen adsorption/ desorption, powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), laser-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (UV-DRS), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) techniques. Oxidative dehydrogenation of ethane to ethylene (ODE) with CO 2 as oxidant was carried out on these catalysts in a fixed-bed reactor at temperatures in the range of 600-700°C and at atmospheric pressure. The changes in structural and textural properties because of sulfate modification were identified. Sulfate modification affected the nature of interaction of CrO x species with the SBA-15 support. During the evaluation, it was observed that sulfate modification enhances ethane conversion and ethylene selectivity of the catalyst. Better dispersion of CrO x and the increase in Cr 6? /Cr 3? ratio seem to be the reasons for the higher performance of the sulfate-modified catalysts compared to that of the unmodified catalyst.

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“…De Rossi et al (6) noted, however, that for higher chromium loadings, clustered (that is, nonredox or type 1 ) chromia could have some catalytic activity. Hakuli et al (8,10) suggested that redox Cr 3+ could fully account for the dehydrogenation activity up to a surface loading of about 5 at Cr nm −2 , and beyond that nonredox Cr 3+ must also have dehydrogenation activity. At low chromium loadings (<5 at Cr nm −2 ) nonredox Cr 3+ would not be catalytically active because it is incorporated inside alumina (10).…”

Section: Effect Of Support On Dehydrogenation Activitymentioning

confidence: 99%

“…Oxidized chromia/alumina catalysts contain chromium in oxidation states Cr 6+ , Cr 5+ , and Cr 3+ (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Cr 6+ and Cr 5+ are reduced by alkanes, hydrogen, and carbon monoxide under typical dehydrogenation conditions (500-600…”

Section: Introductionmentioning

confidence: 99%

Semi-Conductor Industry

Monsalvo¹

2015

Ecological Technologies for Industrial Wastewater Management

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Irreversible deactivation of chromia/alumina dehydrogenation catalysts was investigated by deactivating the catalysts (4 wt% Cr) through prolonged calcination in air at temperatures up to 1200• C. Nitrogen physisorption, X-ray diffraction, diffuse reflectance spectroscopy in the UV-visible region, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and catalytic measurements revealed that two deactivation mechanisms were responsible for the formation of catalytically inactive aluminaincorporated Cr 3+ species: (i) entrapment of Cr 3+ ions inside the alumina support during sintering of the alumina support and (ii) migration of Cr 3+ ions into the alumina support. Chromia that had been impregnated on alumina inhibited the phase transformation from γ-to α-alumina.

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Initial Activity of Reduced Chromia/Alumina Catalyst inn-Butane Dehydrogenation Monitored by On-Line FT–IR Gas Analysis

Cited by 77 publications

References 0 publications

Monitoring Chromia/Alumina Catalysts in Situ during Propane Dehydrogenation by Optical Fiber UV–Visible Diffuse Reflectance Spectroscopy

Monitoring Chromia/Alumina Catalysts in Situ during Propane Dehydrogenation by Optical Fiber UV–Visible Diffuse Reflectance Spectroscopy

Oxidative dehydrogenation of ethane with carbon dioxide over Cr2O3/SBA-15 catalysts: the influence of sulfate modification of the support

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