Chemical Reactivity of Binary Rare Earth Oxides

Bernal, S.; Blanco, Ginesa; Gatica, José M.; Pérez-Omil, Jose A.; Pintado, José

doi:10.1007/1-4020-2569-6_2

Cited by 17 publications

(24 citation statements)

References 384 publications

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“…The TPD-MS diagrams for CO 2 (m/z D 44) desorption from the series of ceria-supported lanthana and pure ceria samples are depicted in Fig. 1; whereas Table 1 accounts for the quantitative data for CO 2 desorption as determined by integration of the corresponding TPD-MS traces.…”

Section: Resultsmentioning

confidence: 99%

“…3 -5 Lanthana, however, has a major drawback; it is highly active against atmospheric water and carbon dioxide. 2,6,7 As a result, when manipulated in the air, it rapidly undergoes profound chemical, structural, and textural modifications. 2 In terms of catalytic applications, this lack of stability makes pure lanthana a material with severe handling problems.…”

Section: Introductionmentioning

confidence: 99%

“…1 The rare earth oxides are acknowledged to belong to this category. 2,3 Among them, the lanthanum sesquioxide, La 2 O 3 , is known to exhibit the strongest basic character in the series. 3 -5 Lanthana, however, has a major drawback; it is highly active against atmospheric water and carbon dioxide.…”

Section: Introductionmentioning

confidence: 99%

“…On the contrary, ceria, though not so strong a base material, 3 -5 shows a much higher stability in air. 2 Accordingly, it seemed interesting to us, to explore the basicity of materials resulting from the surface modification of ceria with highly dispersed lanthana. A number of references in the literature have dealt with acid-base 4,5 properties of La-Ce mixed oxides, but no similar information is presently available on ceria-supported lanthana systems.…”

Section: Introductionmentioning

confidence: 99%

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Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Bernal

Blanco

Amarti

et al. 2006

Surface & Interface Analysis

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The surface basicity of pure ceria is strongly enhanced by the presence of the supported La 2 O 3 , the effect being very much influenced by the calcination temperature. X-ray diffraction (XRD), Raman spectroscopy, and La 3d 5/2 XPS data for the different samples show a progressive incorporation of La 3+ into the ceria lattice as the calcination temperature is increased. This structural change is considered to be responsible for the modifications that occurred in the basicity of the lanthana-modified ceria samples as revealed by temperature-programmed desorption-mass spectrometry (TPD-MS) of pre-adsorbed CO 2 .

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Bernal

Blanco

Amarti

et al. 2006

Surface & Interface Analysis

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“…[7,13] CO 2 desorption from the samples exposed to the atmosphere can be used to compare the relative basicity of the catalyst before and after the impregnation with rhodium. Figure 4 shows TPD-MS traces for CO 2 (m/e: 44) desorption.…”

Section: Resultsmentioning

confidence: 99%

Actual constitution of the mixed oxide promoter in a Rh/Ce_1−xPr_xO_2−y/Al₂O₃ catalyst. Evolution throughout the preparation steps

Aboussaïd¹,

Bernal²,

Blanco³

et al. 2008

Surface & Interface Analysis

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The evolution of the ceria-praseodymia mixed oxide promoter throughout the successive steps involved in the preparation of a 3% Rh/25% Ce 0.8 Pr 0.2 O 2−x /Al 2 O 3 -3.5% SiO 2 catalyst is studied with the help of X-ray diffraction (XRD), spatially resolved electron energy loss spectroscopy (EELS), XPS, and thermal programed desorption (TPD) techniques. Incipient wetness impregnation has been used to obtain the appropriate loading of this promoter. As revealed by XRD, EELS, and XPS data, the alumina-supported CeO 2 -PrO 2−x mixed oxide sample consisted of a bimodal distribution of the particles of the promoter. XRD shows two fluorite-like phases: cerium-rich particles with a mean crystallite size greater than 6 nm and smaller praseodymium-rich crystals, about 3.5 nm size. Surface Ce/Pr ratio obtained by XPS was consistent with a higher dispersion of the praseodymium-rich oxide particles. The final Rh catalyst was prepared in a second step, by impregnation of the CePrO x /Al 2 O 3 system with an acidic solution of Rh(NO 3 ) 3 . The low pH of this solution is responsible for further modifications of the lanthanide oxides distribution. Thus, there is a redispersion of the praseodymium-rich phase, which is evidenced by EELS and XPS data. Likewise, CO 2 desorption from samples exposed to the atmosphere is consistent with an enhanced basicity of the sample due to the increase of Pr 3+ content at the surface of the catalyst. The observed changes on the nanostructure of the mixed oxide promoter can be attributable to a partial dissolution of the oxide, selectively leaching Pr 3+ cations from the lattice, which are finally deposited as small particles after the drying steps of the preparation.

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Fast escape of hydrogen from gas cavities around corroding magnesium implants

et al. 2013

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Magnesium materials are of increasing interest in the development of biodegradable implants as they exhibit properties that make them promising candidates. However, the formation of gas cavities after implantation of magnesium alloys has been widely reported in the literature. The composition of the gas and the concentration of its components in these cavities are not known as only a few studies using non-specific techniques were done about 60 years ago. Currently many researchers assume that these cavities contain primarily hydrogen because it is a product of magnesium corrosion in aqueous media. In order to clearly answer this question we implanted rare earth-containing magnesium alloy disks in mice and determined the concentration of hydrogen gas for up to 10 days using an amperometric hydrogen sensor and mass spectrometric measurements. We were able to directly monitor the hydrogen concentration over a period of 10 days and show that the gas cavities contained only a low concentration of hydrogen gas, even shortly after formation of the cavities. This means that hydrogen must be exchanged very quickly after implantation. To confirm these results hydrogen gas was directly injected subcutaneously. Most of the hydrogen gas was found to exchange within 1h after injection. Overall, our results disprove the common misbelief that these cavities mainly contain hydrogen and show how quickly this gas is exchanged with the surrounding tissue.

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Chemical Reactivity of Binary Rare Earth Oxides

Cited by 17 publications

References 384 publications

Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Actual constitution of the mixed oxide promoter in a Rh/Ce_1−xPr_xO_2−y/Al₂O₃ catalyst. Evolution throughout the preparation steps

Fast escape of hydrogen from gas cavities around corroding magnesium implants

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Chemical Reactivity of Binary Rare Earth Oxides

Cited by 17 publications

References 384 publications

Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Surface basicity of ceria‐supported lanthana. Influence of the calcination temperature

Actual constitution of the mixed oxide promoter in a Rh/Ce1−xPrxO2−y/Al2O3 catalyst. Evolution throughout the preparation steps

Fast escape of hydrogen from gas cavities around corroding magnesium implants

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Actual constitution of the mixed oxide promoter in a Rh/Ce_1−xPr_xO_2−y/Al₂O₃ catalyst. Evolution throughout the preparation steps