Cerium oxide CeO

Fig. 7.4 High-resolution transmission electron microscopy (TEM) image of a rhodium on a modified cerium oxide (Ceo.gTbo.202 x) after reduction, showing how the metal is almost epitaxially attached to the support, (a) TEM image (b,c) digital diffraction patterns obtained by Fourier transformation from the images (d) structure model ...

Cerium oxide (CeO ) was deposited onto a (100) LaAlOj single-crystal substrate with a single cube texture and good in- and out-ofplane alignment. A cp scan of the (220) plane of the CeO film yielded a FWHM of 2.45 ° 0.05 ° the rocking curve of the (200) plane indicated a FWHM of 1.688° 0.006°. A layer of YSZ was then deposited by CCVD on top of this ceria layer. The majority of the YSZ deposited as one cube texture (Figure 3) with only a minor 45° film rotation (<1% intensity) present. The... 

The three-component condensation of aldehydes, p-ketoesters, and urea has been carried out in water using ceria (cerium oxide, CeO,) NPs supported on poly(4vp-co-dvb) as a catalyst for the preparation of 3,4-dihydropyrimidin-2(l//)-ones in good yields [97] (Scheme 5.43). 

The sole commercially available cerium oxide CeO, dissolves in HCl to give hydrated CeCl3, and Tb O likewise is reduced to hydrated TbCl3. (CeO gives Ce salts only if dissolved in oxidising acids, e.g. HNO3, H SO. ) The corresponding fluorides are insoluble and can be precipitated from aqueous solution and may be hydrated. 

The compound cerium oxide (either Ce Oj or CeO ) is used to coat the inside of ovens because it was discovered that food cannot stick to oven walls that are coated with cerium oxide. Cerium compounds are used as electrodes in high-intensity lamps and film projectors used by the motion picture industry. Cerium is also used in the manufacturing and polishing of high-refraction lenses for cameras and telescopes and in the manufacture of incandescent lantern mantles. It additionally acts as a chemical reagent, a misch metal, and a chemical catalyst. Cerium halides are an important component of the textile and photographic industries, as an additive to other metals, and in automobile catalytic converters. Cerium is also used as an alloy to make special steel for jet engines, solid-state instruments, and rocket propellants. 

In all these applications and related studies, CeO is seldom used alone but it often employed in combination with other oxides or in conjunction with active metals (nobles metals or Ni, Ag. Cu) and thermally stable supports. Therefore strictly speaking, ceria may function either as structural/electronic promoter or as cocatalyst, depending on the type of application, but not as a true catalyst, although the amount of cerium oxide which is used in certain catalyst formulations may easily exceed 20-30 wt. %. 

The structure of a highly active cerium-molybdenum-tellurium acrylonitrile catalyst(l ) has previously been described in terms of binary (Ce,Mo)0 and ternary (Ce,Mo,Te)0 phases( ). It was concluded that none of the constituent oxides (CeO, ... 

However, there is much that remains unknown and in particular it is not known how the above phenomenon (Eq. 14.12) reflects the catalyst performance. Fig. 14.10 shows the change in the rate constant k (mol s ) of the oxidation of phenol with the change in the Cu content. The rate constant (k) linearly increases with the Cu content regardless of the calcination temperature of the catalysts. Thus, the active component in CCi Cup g catalysts is Cu. In the subsequent work, they reported that sol-gel technique is better than co-precipitation method, and high dispersion of copper oxide phase on the cerium oxide causes high catalytic activity. They emphasized the importance of the combination of the mixed valence state of Ce and Ce caused by an incorporation of Cu, which causes the reversible addition and removal of oxygen in this inherently defect structure. Here, the defect structure in CeOj is also emphasized. However, their discussion is rather sophisticated and their claim on the inherent function of this catalyst is difficult to be understood. The clear point is that copper in this catalyst is considerably active and durable in the wet-oxidation condition due to the effect of CeO,. 

The reactions between cerium trichloride and oxide ions were initially studied in the pure KCl-NaCl equimolar mixture at 1000 K by the method of potentiometric titration using a calcium-stabilized zirconia membrane electrode. The titration curves clearly demonstrated the existence of the soluble cerium oxychloride CeO+ and precipitated cerium oxide ... 

The TPR spectrum of pure Ce02 oxide (Fig. 5) is similar to those noticed on cerium oxides of various specific surface areas [3,10]. The first peak (T = 604°C) may correspond to the reduction of a surface oxygen species related to Ce [3]. Johnson et al [10] have shown that the position of this peak shifts to lower values of Tm when the specific surface area of the solids increases. The hydrogen consumption detected at high temperatures (Fig. 5) was also noticed by the various authors [3, 10] and was attributed to the reduction of the bulk Ce02 oxide. The differences in the TPR spectra of the washcoat without PM and of the CeOo oxide can be interpreted by the existence of interactions between CeO and AI2O3 [3]. 

The nebulizer gas should be optimized for signal intensity, lowest possible cerium oxide formation and highest possible uranium signal. RF power is typically optimized at 1200-1300 W. The exact parameters depend on the instrument and introduction system. A PerkinElmer Sciex Q-ICP-MS should be optimized to obtain the highest possible stable signal with no more than 2.5% CeO" formation with a standard introduction system. If the preferred Peltier-cooled system is used, CeO" should be optimized to less than 1.8%. 

In this area, Yang and colleagues have designed a bilayer stracture by combining platinum and cerium oxide nanocube into sub-lOnm layers on silica substrate [7]. Two distinct reactions can be utilized on a bilayer structure with two metal-metal oxide interfaces (CeO -Pt and Pt-SiO ). The CeO -Pt interface is used to catalyze the decomposition of methanol into CO and H, while ethylene hydroformylation happens on the Pt-SiO interface. This is an intriguing concept on making nanocrystal bilayer structures designed for the application of multifunctional catalysts, the so-called tandem catalyst. 

Baron M, Bondarchuk O, Stacchiola D, Shaikhutdinov S, Freund HJ (2009) Interaction of gold with cerium oxide supports CeO (111) thin films vs ceox nanoparticles. J Phys Chem C 113 6042-6049... 

The same behavior occurs on the Ceo.8Feo,202-5 mixed oxide. It was proven through diffuse reflectance spectroscopy (DRS)-UV-Vis experiments. The spectrum (not shown) exhibited different bands corresponding to different wavelengths. For the pure cerium oxide, the bands at 240, 280, and 340 nm are associated with the f- d transition species of Ce " (0 Ce " ), with charge transfer of Ce for low coordination (0 Ce ), and with an interme-... 

Phase X-ray diagrams of solid solution based on cerium dioxide, obtained by synthesis via carbonates using 95% of precipitator is presented in Fig. 15.1. The research has shown that samples with fluorine mass fiaction less than 2% contain only one phase cerium oxide, except for the sample containing 0.5% fluorine. Further introduction of fluorine from 3 to 8% leads to oxyfluoride phase (LnOF) separation. There are three phases (CeO, LnOF and LnFj) when fluoride content is more than 9%. Samples with 80% of precipitator have the same phase composition. The residts of the quantitative phase and structural analysis of samples, synthesized via... 

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