Raman spectroscopy and X-ray diffraction study of the phase transformation of ZrO2–Al2O3 and CeO2–Al2O3 nanocomposites

Boullosa-Eiras, Sara; Vanhaecke, Estelle; Zhao, Tong; Chen, De; Holmén, Anders

doi:10.1016/j.cattod.2010.05.038

Cited by 52 publications

(13 citation statements)

References 40 publications

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“…Figure reports the Raman spectrum of the synthesized catalyst in the range of 100–1200 cm –1 . The absence of Raman peaks for MAs is because of the ionic characteristic of the Al–O bond . The VO x spectrum not only is a function of the vanadium loading but also depends on the type and concentration of the surface species.…”

Section: Resultssupporting

confidence: 66%

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Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

et al. 2020

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High-performance, fluidizable VO x /Ce-meso-Al 2 O 3 catalysts were prepared by an excessive solvent approach. The prepared catalysts were characterized using various physicochemical techniques in order to secure desired properties. XRD, Raman, and FTIR analyses indicated the presence of amorphous VO x phases on Ce-meso-Al 2 O 3 . Nitrogen adsorption isotherm analysis confirmed a mesoporous framework with a high surface area of the catalysts. H 2 -TPR reduction showed an active and stable behavior of the catalysts in repeated reduction and oxidation cycles. The NH 3 -TPD and NH 3 desorption kinetics analysis revealed that the synthesized catalysts have moderate acidities and low activation energies of NH 3 desorption, suggesting weak metal−support interactions. The VO x /Ce-meso-Al 2 O 3 catalysts were evaluated for n-butane oxidative dehydrogenation (BODH) using a fluidized CREC riser simulator under gas-phase oxygen-free conditions. The reaction time and reaction temperature were varied between 5 and 25 s and 450−575 °C, respectively. It was found that BODH with 0.2 wt % cerium-doped VO x /meso-Al 2 O 3 catalysts gives the highest selectivity (62.3%) of C4 olefins with a conversion of 10.6% at 450 °C and 5 s. Furthermore, the fluidizable VO x /Ce-meso-Al 2 O 3 catalyst showed a stable performance over repeated feed injections followed by catalyst regeneration cycles for BODH.

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Section: Resultssupporting

confidence: 66%

“…The absence of Raman peaks for MAs is because of the ionic characteristic of the Al−O bond. 67 The VO x spectrum not only is a function of the vanadium loading but also depends on the type and concentration of the surface species. In the 0.2 Ce catalyst, the only weak band is detected at 1130 cm −1 .…”

Section: Reactor Systemmentioning

confidence: 89%

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

et al. 2020

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“…A comparison of the UV and visible Raman spectra provides information on species distribution. [45][46][47][48] For visible Raman of CaO-SG and CaO-IM samples (Figure 5a), the band near to 357 cm -1 is due to the vibration of the Ca-O bond in CaO, 714 cm -1 for ZrO2 and the bands at 211, 262, 284, 357, 438, 546 cm -1 correspond to well-known intense bands for CaZrO3. 49,50 Presence of CaO, ZrO2 and CaZrO3 phases confirmed from visible Raman spectra (Figure 5a) are in good agreement with the phases (CaO, ZrO2 and CaZrO3) observed in XRD pattern (Figure 1).…”

Section: Resultsmentioning

confidence: 92%

CaO Nanoparticles Coated by ZrO₂ Layers for Enhanced CO₂ Capture Stability

Sultana

Tran

Walmsley

et al. 2015

Ind. Eng. Chem. Res.

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BRIEFS. Coating a ZrO2 layer on CaO nanoparticles significantly stabilized the solid CO2 sorbents in the presence of steam.ABSTRACT. CaO is an attractive CO2 acceptor, due to its good kinetics and high capture capacity, even under low CO2 concentration condition. The major problem associated with CaO acceptors is the loss of CO2 capture capacity during cyclic operations. The declining performance of the CaO acceptors is more pronounced in the presence of steam. In this paper we propose a method for fabrication of nano-CaO acceptors with a coated ZrO2 layer to improve the stability. The nano-CaO acceptor was prepared by thermaldecomposition method following a coating process by solgel, incipient wet impregnation or hydrolysis, respectively. The thermogravimetric analysis (TGA) of the cyclic process of CO2 carbonation/decarbonation revealed that the nanoCaO acceptors with sol-gel (CaO-SG) and wet impregnation (CaO-IM) coating have higher CO2 capture capacity and a longer life time than the uncoated ones. The capture capacity of CaO-IM declined after 14 cycles whereas CaO-SG remained stable upto 20 cycles. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra were used to characterize the coated and uncoated nano-CaO structures. Combined characterization techniques showed that a CaZrO3 layer was formed around the nano-CaO particles by sol-gel coating. Multi-cycle carbonation/decarbonation processes were performed in absence and presence of steam in CO2 capture kinetic experiments as well as at the sorption enhanced reforming conditions, and CaO nanoparticles with surface CaZrO3 layer showed a promising cyclic stability.

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“…2 Influence of sulfur on the mass variations of samples oxidized at 900°C during 24h under dry air and water vapor + Ar mixture Similar oxides were detected in zone B (protuberated oxides), but interestingly the main Raman mode of Cr2O3 (at 551 cm -1 ) was often much more intense than the main spinel' peak, suggesting a larger volume fraction of Cr2O3 in this thick external oxide layer as compared to the thinner of zone A (figure 4.a). Besides, in zone C (internal oxidation area), two different polymorphs of alumina were identified with a pair of fluorescence peaks located at 1179 cm -1 and 1239 cm -1 and another at 1374 cm -1 and 1404 cm -1 that could be attributed respectively to -Al2O3 [45,46], and α-Al2O3. AlN is also detected locally with Raman peaks located at 617 cm -1 and 657 cm -1 [47], on platelet-like morphologies, shown on figures 3.d, 3.e and 3.f.…”

Section: Resultsmentioning

confidence: 99%

Influence of Sulfur and Water Vapor on High-Temperature Oxidation Resistance of an Alumina-Forming Austenitic Alloy

et al. 2021

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The oxidation behavior of alumina-forming alloys was studied after oxidation treatments performed at 900°C for 24h in air or in steam. Alloys with sulfur contents ranging from 1 to 82 ppm in wt% were used. The influence of sulfur presence as a trace element as well as the presence of steam in the oxidizing atmosphere were investigated.Under oxidation conditions, higher sulfur contents led to higher mass gains and the trend is more pronounced in steam than in air. Oxides were identified by Raman spectroscopy: a thin and continuous α-Al2O3 layer was formed at the metal-oxide interface in all cases. The mass gain differences were caused by other oxides formed at the surface of the samples -mainly spinel and Cr2O3 -and in the internal oxidation zone too -mainly α-Al2O3 and -Al2O3 -indicating that the protectiveness of the alumina layer greatly depends on the sulfur content in the base material and the oxidizing atmosphere. In order to explain this phenomenon, oxide structures were analyzed at various scales using Scanning Electron Microscopy, Transmission Electron Microscopy and Nanoscale Secondary Ion Mass Spectrometry. Sulfur was detected at metal-oxide interfaces and also in the alumina layer in regions enriched with chromium. Besides, we demonstrate that steam oxidation leads to finer alumina grains as compared to air oxidation. Finally, the relationship between oxidation conditions, nanoscaled structural features and oxidation kinetics are discussed.

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Raman spectroscopy and X-ray diffraction study of the phase transformation of ZrO2–Al2O3 and CeO2–Al2O3 nanocomposites

Cited by 52 publications

References 40 publications

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

CaO Nanoparticles Coated by ZrO₂ Layers for Enhanced CO₂ Capture Stability

Influence of Sulfur and Water Vapor on High-Temperature Oxidation Resistance of an Alumina-Forming Austenitic Alloy

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Raman spectroscopy and X-ray diffraction study of the phase transformation of ZrO2–Al2O3 and CeO2–Al2O3 nanocomposites

Cited by 52 publications

References 40 publications

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VOx/Ce-meso-Al2O3 under Gas-Phase Oxygen-Free Conditions

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VOx/Ce-meso-Al2O3 under Gas-Phase Oxygen-Free Conditions

CaO Nanoparticles Coated by ZrO2 Layers for Enhanced CO2 Capture Stability

Influence of Sulfur and Water Vapor on High-Temperature Oxidation Resistance of an Alumina-Forming Austenitic Alloy

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Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

CaO Nanoparticles Coated by ZrO₂ Layers for Enhanced CO₂ Capture Stability