Abstract: A process for producing a high-temperature resistant honeycomb catalyst, which comprises admixing cerium, zirconium, at least one metal selected from the group consisting of iron and nickel, at least one metal selected from the group consisting of platinum, palladium and rhodium, and optionally at least one metal selected from the group consisting of neodymium, lanthanum and praseodymium, each in the form of an aqueous solution or dispersion of a soluble or easily water-dispersible compound of the metal, with active alumina, drying the mixture, calcining it, dispersing the resulting catalyst composition in an aqueous medium, and depositing the dispersion on a monolithic honeycomb carrier. The resulting catalyst is useful for simultaneous conversion of hydrocarbons, carbon monoxide and nitrogen oxides in an exhaust gas.

Abstract: A B S T R A C T: The adsorption of cerium(IV) by both natural and Na-exchanged kaolinite from aqueous solutions of ceric ammonium nitrate was studied in equilibrium systems. Cerium may be adsorbed either as a monomeric species or as a polymeric hydroxy cation. The species adsorbed depends on the concentration of cerium in the stock solution, the age of this solution prior to the preparation of the equilibrium system and on the equilibration period. Adsorbed cations undergo polymerization on the surface of the kaolinite; the resulting polymeric species forms strong bonds with the clay surface--it is not desorbed by sulphuric acid--and may be considered fixed. Adsorption of cerium reaches a maximum in solutions containing 0.15 M sulphuric acid. Very little is known about the adsorption of lanthanides by clay minerals, although this process seems to be important in the geochemical cycle of these elements. Recently, the adsorption of a few lanthanides by montmorillonite was investigated by Bruque et al. (1980) and Miller et al. (1982, 1983). The present communication deals with the mechanism of adsorption of cerium by kaolinite.

Abstract: Etude de l'oxydation de films de niobium revetus de couches monomoleculaires de cerium, par spectrometrie de photoelectrons RX. Il se forme des quantites significatives de Nb 2 O 5 a des pressions aussi faibles que 6,6•10 −6 Pa, favorisees par la couche de ceAnalyse quantitative cSilicium|ANAst GravimetriehanAlliage2 A:>50 Si:10-15rium (trivalent en tetravalent) au cours de l'oxydation. La cinetique de formation de Nb 2 O 5 sans le cerium oxyde comporte deux etapes, une rapide et une lente

Abstract: An aqueous acidic peroxide-free solution and process for treating receptive metal surfaces to impart a chromium passivate film thereon containing chromium ions substantially all of which are present in the trivalent state, hydrogen ions to provide a pH of about 1.2 to about 2.5, at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanide mixtures as well as mixtures thereof present in an amount effective to activate the formation of the chromate passivate film and nitrate ions as the essential oxidizing agent present in an amount to provide a mol ratio of nitrate ions to chromion ions and activating metal ions of at least about 4:1 and sufficient to activate the hydrated trivalent chromium to form a chromate film on the substrate. The aqueous acidic solution can optionally, and preferably further contain controlled amount of sulfate ions, halide ions, organic carboxylic acids, a bath soluble and compatible silicate compound, and one or a combination of wetting agents to further enhance the characteristics of the passivate film produced.

Abstract: A pollution control catalyst for a catalytic converter in the exhaust system of an internal combustion engine, which catalyst comprises a support impregnated with (i) at least one platinum group precious metal, and with (ii) cerium base metal, or a combination of cerium and at least one other base metal, is facilely prepared by (1) impregnating a catalyst support with precursor compounds of said cerium base metal, or of said cerium base metal and of at least one other base metal, (2) activating said impregnated support, under a neutral or oxidizing atmosphere, at a temperature ranging from 120° to 800° C, (3) impregnating said catalyst support with precursor compounds of said at least one platinum group precious metal, together with a delayed-action organic reducing agent, inactive under cold conditions, which effects reduction of said platinum group precious metal precursor compounds, but not of any cerium or other base metal precursor compounds, under the conditions of the step (4) below, and (4) activating said impregnated catalyst, also under a neutral or oxidizing atmosphere, at a temperature ranging from 300° to 800° C

Abstract: The nuclide 138La decays to 138Ce and 138Ba by β− and electron capture, respectively, with a total half life of about 1×105 Myr. Rankama1 suggested the possibility of age determination using this radioactive decay system. Recently, Tanaka and Masuda succeeded in age determination by using the 138La–138Ce geochronometer for a gabbro from the Bushveld complex, South Africa. This La–Ce isotopic system, coupled with the Sm–Nd system, provides a new isotope tracer2,3 for the geo- and cosmochemical samples, especially for samples having a Ce anomaly in the rare-earth element patterns. Meteoritic primordial composition of cerium isotopes can serve as a basis for La–Ce systematics. Furthermore, Ce isotopic compositions for meteorites will provide information concerning half-life data of the 138La decay system, which remains uncertain. Here, cerium isotope ratios were determined for Juvinas, Pasamonte and ALH-78132 eucrites and the Jilin (H4) chondrite. Neodymium isotope ratios and abundances of lanthanum, cerium, neodymium and samarium were also determined for these meteorites.

Abstract: A method of electrowinning a metal such as aluminum from e.g. a cryolite based melt containing alumina employs an enode having as its operative surface a protective coating which is maintained by the presence of constituents of the coating dissolved in the melt. The protective coating is preferably a fluorine-containing cerium oxycompound electro-deposited in-situ from cerium species dissolved in a fluoride-based melt.

Abstract: The use of cerium chloride for the localization of thiamine-pyrophosphatase (TPPase) in rat liver parenchymal cells has been investigated and the results are compared with the classical lead capture method. A medium containing 3 mM cerium chloride gave the most uniform and consistent results with a homogeneous electron dense reaction product in the first trans lamella of the Golgi complex and a weak staining of endoplasmic reticulum. The fine deposits of cerium phosphate filled completely the first trans Golgi cisterna. In contrast the reaction product of the lead-based method appeared clumpy and aggregated with an irregular distribution over both Golgi complex and endoplasmic reticulum. Higher and lower concentrations of cerium chloride than 3 mM gave inconsistent results. The present study demonstrates that the cerium-based method is superior to the classical lead-technique for the localization of TPPase.

Abstract: Cerium based glass polishing compositions, well adapted for the polishing, e.g., of optical glass, are comprised of (i) at least one crystalline phase of CeO 2 type, and (ii) a crystalline phase which comprises a rare earth pyrosilicate having the formula Ln 2-x Ce x Si 2 O 7 , wherein Ln is at least one lanthanide or yttrium and x is a number ranging from zero to less than 2.

Abstract: An improved fuel for operating a diesel engine equipped with a particulate trap contains a combination of a cerium naphthenate additive and a manganese dioxide additive.

Abstract: Catalytic cracking catalysts and catalytic cracking process wherein the cracking catalysts are prepared by: (1) contacting a mixture of a large pore zeolite and an inorganic oxide matrix at effective conditions of temperature, pH and time with a fluoro salt; and (2) ammonium exchanging the product of step (1) to provide a catalyst having less than 03 percent by weight Na 2 O Optionally, the product is provided with an effective amount of at least one cation selected from the class consisting of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, lutetium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium

Abstract: The Soxhlet-type leaching test was carried out on borosilicate glass that contained 14 wt% simulated high-level waste. The morphology, texture, composition, and crystallography of the surface layers that formed were examined using optical microscopy, scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy. Four surface layers, made up of 100- to 1000-A crystalline and noncrystalline particles, formed on the glass. The elements found were classified into three groups based on their behavior in the surface layers. Group I contained the alkali metals, such as sodium, potassium, and cesium, which were strongly depleted from the layers as a result of leaching. Group II contained elements such as manganese, iron, nickel, zirconium, lanthanum, cerium, and neodymium, which were more concentrated in the surface layers than in the unleached part of the specimen, probably because the layers had shrunk during the drying process. Group III contained the elements which behaved inconsistently as a group: Some, such as calcium, silicon, and aluminum, were poor in the layers; magnesium and barium were present, but had concentration profiles that differed from those of Group II. Only one crystalline phase, a sheet silicate, formed in the layers. It had the expected chemical form, (Ca, Ba, La,more » Ce, Nd) /sub x/ (Mn, Fe, Zr, Mg, Ni, Al) /sub y/ (Si, Al) /sub z/ (O, OH) /sub m/ ; its formation probably influenced the leaching mechanisms.« less

Abstract: Disclosed is a bleaching solution or bleach-fixing solution for a light-sensitive silver halide photographic material, which comprises an oxidizing agent comprising a diethylenetriaminepentaacetic acid iron (III) complex salt, and at least one metal ion selected from the group consisting of nickel, cobalt, zinc, cerium, ruthenium, yttrium, samarium, magnesium, calcium, bismuth, strontium, manganese, aluminum, tin, barium, indium, thallium and zirconium. In another embodiment, the solution may further contain a chelating agent other than diethylenetriaminepentaacetic acid.

Abstract: Amorphous samples of a new inorganic ion exchanger, cerium(IV) selenite have been prepared under varying conditions. The material prepared by mixing 0.025M ceric sulfate and 0.025M sodium selenite in the ratio of 1∶1 was studied in detail for its ion-exchange capacity, chemical stability, IR, thermogravimetry and Kd values. Separations of metal ions have been performed on columns of this ion exchanger.

Abstract: The oxidation of 1,2- diphenylethane and 2,3-dimethyl-2,3-diphenylbutane by cerium(IV) ammonium nitrate and Co(OAc)3 in acetic acid show that a radical cation mechanism is plausible only in the reaction of the former oxidant.

Abstract: The crystal and molecular structure of the title complex has been determined by the use of the single-crystal X-ray diffraction method. The crystal of CeC21H17O10, F. W. 569.48, was monoclinic; space group P21⁄c, a=13.401(2), b=19.173(5), c=8.079(1) A, β=98.94(1)°, U=2050.6(8) A3, Z=4, Dm=1.84(3), Dx=1.84 Mg m−3, and μ(Mo Kα)=2.31 mm−1. Each cerium(III) atom is ennea-coordinated and is in a tri-capped trigonal-prism geometry. They are in a linear polymer, and each cerium(III) atom is bridged to the next metal atom by three carboxylate ligands.

Abstract: We demonstrate the common physical origin, lying in $f$-electron-band-electron hybridization, of the anomalous crystal-field-splitting reduction and of the two-ion interaction giving magnetic ordering, for cerium systems with moderately delocalized $f$ electrons.

Abstract: One or more monolayers of cerium arrayed on the surface of a niobium metal acts as a catalyst to oxidation of the niobium at ambient temperature and results in a very thin, very high quality insulating layer which may be configured by patterning of the catalyst Significant amounts of Nb 2 0 5 are formed at pressures as low as 66x 10 -6 Pa, promoted by the presence of the cerium This catalytic activity is related to the trivalent to tetravalent valence change of the cerium during oxidation The kinestics of Nb 2 0 5 formation beneath the oxidation cerium shows two stages: the first stage is fast growth limited by ion diffusion; the second stage is slow growth limited by electron tunnelling Other catalytic rare earths usable instead of cerium are terbium and praseodymium; other substrate materials usable instead of niobium are aluminium, hafnium, silicon and tantalum, or oxidizable alloys thereof

Abstract: A process for oxidizing an organic compound by ceric sulfate dissolved in an aqueous sulfuric acid solution, wherein the organic compound is oxidized (1) by means of a ceric sulfate-aqueous sulfuric acid solution or a cerous sulfate-containing ceric sulfate-aqueous sulfuric acid solution in which the molar concentration (mol/liter) of ceric sulfate is at least the molar concentration of cerium (ions) contained in the molecules of cerous sulfate at the maximum solubility of cerous sulfate in an aqueous sulfuric acid solution at the final sulfuric acid concentration (exclusive of ceric sulfate and cerous sulfate) and at the temperature under the oxidation reaction conditions and at most the saturated molar concentration of ceric sulfate in said aqueous sulfuric acid solution, (2) under a condition such that at the end of the oxidation reaction, the concentration of ceric sulfate is maintained at a level capable of dissolving cerous sulfate which is present at a concentration of at least the maximum solubility of cerous sulfate in said aqueous sulfuric acid solution.