Showing papers on "Cerium published in 2001"
TL;DR: In this article, the authors investigated the relationship between the composition of catalysts and their activity in reducing both phenol concentration and total organic carbon (TOC) by co-precipitation.
Abstract: Mn–Ce–O composite catalysts have been widely used in sub- and supercritical catalytic wet oxidation of toxic organics contained in aqueous streams. In order to investigate their composition–activity relationship, 11 samples with Ce/(Mn+Ce) atomic bulk ratios ranging from 0 to 100% were prepared by co-precipitation. Phenol was selected as a model pollutant and the catalytic oxidation was carried out in a batch slurry reactor using oxygen as the oxidizing agent under mild reaction conditions. The results showed that the catalytic activity was greatly influenced by the catalyst composition. The catalyst with Mn/Ce ratio=6/4 was found to be the most active in reducing both phenol concentration and total organic carbon (TOC). All catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), temperature programmed reduction (TPR) and nitrogen adsorption techniques. Systematic shifts in binding energy, diffraction angle, and reduction temperature were observed in the XPS, XRD and TPR spectra, respectively. XPS and XRD data revealed the occurrence of significant interactions between Mn and Ce oxides, resulting in the evolution of textural, structural and oxidation state with composition. TPR analysis showed that the interaction between Mn and Ce greatly improved the oxygen storage capacity of manganese and cerium oxides as well as oxygen mobility on the surface of catalyst. Catalytic active sites have been ascribed to manganese oxide species exhibiting higher oxidation state. Furthermore, XPS revealed that the most active catalyst, i.e. Mn/Ce 6/4, exhibits an electron-rich surface which may be very important in the activation of adsorbed oxygen.
439 citations
TL;DR: In this article, mixed layers of Al and Ce oxides have been obtained in conversion coatings on two aluminum alloys (AA6061 and AA2618) and the microstructure and the chemical composition of the protective films have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS).
209 citations
TL;DR: A nonionic polymeric adsorbent styrene divinylbenzene, Amberlite XAD-4 was functionalized with o-vanillinsemicarbazone and its analytical properties have been studied as mentioned in this paper.
208 citations
TL;DR: The complexes of cerium( III) and neodymium(III) showed marginal cytotoxic activity against transformed leukemic cell lines (P3HR1 and THP-1) as compared to the inorganic salts.
188 citations
TL;DR: In this article, a few wt.% of cerium salts were investigated as coatings on aluminum alloy 2024-T3, and no change in the oxidation state of the cerium in the sol-gels was found.
Abstract: Corrosion protection is a key requirement for coatings on aircraft as the US Air Force extends the lifetime of its fleet. Coating systems for aluminum have long incorporated chromates in conversion coatings to protect against corrosion, but environmental restrictions require that alternative coating systems be developed. Cerium has been proposed as an alternative to chromate inhibitors, as have several other rare earth elements, because the rare earths behave as cathodic inhibitors in aluminum. Epoxy silicate sol–gels, containing a few wt.% of cerium salts, were investigated as coatings on aluminum alloy 2024-T3. The salts used were cerium(III) chloride, cerium(III) nitrate hexahydrate, and ammonium cerium(IV) nitrate. X-Ray photoelectron spectroscopy (XPS/ESCA) was used to study both the doped sol–gels and reference cerium compounds in order to determine the oxidation state of the cerium at the surface of the sol–gel coatings. No change in the oxidation state of the cerium in the sol–gels was found. Coupled with electrical impedance spectroscopy measurements, the incorporation of cerium into sol–gels seems promising for future corrosion protection of aluminum 2024-T3.
181 citations
TL;DR: A synthetic material with solar elemental proportions of iron, magnesium, silicon, titanium, calcium, and aluminum oxides and doped with rare earth elements was evapated in a vacuum furnace at 1800 and 2000°C for different durations to study its chemical and isotopic evolution during the evaporation process.
145 citations
TL;DR: Lanthanum and cerium chloride and their binary mixtures have been investigated as corrosion inhibitors of AA5083 Al-Mg alloy in aerated 35% NaCl aqueous solution as discussed by the authors.
140 citations
TL;DR: In this article, X-ray diffraction revealed that the prepared doped particles had cubic fluorite structures, although the peak positions changed depending on the kind and amount of the doped metal ion.
134 citations
TL;DR: In this paper, a mimic alkoxide method was used to synthesize nanocrystalline CeO 2 powders of high sinterability, which employed alcohols as solvent, cerium nitrate hexahydrate as source and diethylamine (DEA) as precipitant.
115 citations
TL;DR: A wide variety of epoxides and aziridines were converted to the corresponding β-halohydrins and β-haloamines using cerium(III) chloride and the cerium-III chloride/NaI system in acetonitrile.
104 citations
TL;DR: Bromination of alkenes using a combination of potassium bromide and cerium(iv) ammonium nitrate (CAN) in a two phase system consisting of water and dichloromethane affords the corresponding dibromides in excellent yield as mentioned in this paper.
Patent•
18 Dec 2001TL;DR: In this article, a lean NOx catalyst and method of preparing the same is described, which includes a ceramic substrate, an oxide support material, and a metal promoter or dopant introduced into the support material.
Abstract: A lean NOx catalyst and method of preparing the same is disclosed. The lean NOx catalyst includes a ceramic substrate, an oxide support material, preferably γ-alumina, deposited on the substrate and a metal promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium, cerium, vanadium, oxides thereof, and combinations thereof. The γ-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between about 80 to 350 m 2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to 0.2 weight percent. In a preferred embodiment the γ-alumina is prepared by a sol-gel method, with the metal doping of the γ-alumina preferably accomplished using an incipient wetness impregnation technique.
TL;DR: This work has investigated more directed methods for preparing triple deckers of a given type with distinct metals in each layer and employs in situ formation of the lanthanide reagent EuCl or CeI[N(SiMe3)2]2, which upon reaction with a porphyrin affords the half-sandwich complex.
Abstract: The use of lanthanide triple-decker sandwich molecules containing porphyrins and phthalocyanines in molecular information storage applications requires the ability to attach monomeric triple decker...
TL;DR: In this paper, a target material for r.f.-sputtering thin-film deposition onto suitable substrates has been used, and the films obtained have been characterized before and after electrochemical lithium intercalation.
Abstract: Research studies on new materials have shown that cerium-vanadium mixed oxides have potential for use as counter-electrodes in electrochromic devices owing to the combination of the excellent stability and transparency of cerium oxides and the high ion-storage capacity of the vanadium oxides. Among them, cerium orthovanadate (CeVO 4 ) has shown its potentiality as an intercalation electrode of suitable structure into which ions can be inserted reversibly, thus balancing the ion-charge capacity required by WO 3 , which is the colouring electrode in electrochromic devices. In this work, cerium-vanadium stoichiometric oxides (CeO 2 -V 2 O 5 , 1:1 molar ratio) have been used as a target material for r.f.-sputtering thin-film deposition onto suitable substrates. The films obtained have been characterized before and after electrochemical lithium intercalation. Their XPS and x-ray-induced Auger electron spectroscopy spectra have been compared with those obtained with the standard precursor oxides and the results discussed also on the basis of literature data. In order to be able to observe the changes in chemical state and composition expected on film formation, a careful curve-fitting procedure has been used that allows the determination of the background structure and intrinsic satellites for each peak, as reported already in previous papers.
TL;DR: Cerium(IV) ammonium nitrate mediated reaction of sodium arene sulphinate and sodium iodide with alkenes afforded vinyl sulphones in very good yields as mentioned in this paper.
TL;DR: Cerium oxide was introduced into the catalysis field relatively recently, in 1976, and not as a catalyst initially, rather, it was chosen as the key oxygen-storage component of the three-way catalyst (TWC) used in automotive exhausts.
Abstract: Catalysts based on cerium oxide are now used as effective oxidation systems in numerous environmental applications. Cerium oxide was introduced into the catalysis field relatively recently, in 1976, and not as a catalyst initially. Rather, it was chosen as the key oxygen-storage component of the three-way catalyst (TWC) used in automotive exhausts. Accordingly, ceria is used to extend the air/fuel ratio window in the exhaust gas, releasing or accepting oxygen, respectively, under fuel-rich or fuellean conditions, so that the noble metal catalyst operates at the desirable stoichiometric air/fuel ratio, at which it effectively converts all three gaseous pollutants—CO, hydrocarbons, and NO—to innocuous products. A solid solution of cerium and zirconium oxides is used in today's catalytic converters because of its higher oxygen-storage capacity (OSC) compared with pure ceria. In the years that followed the introduction of ceria into the catalytic converter, many additional merits of cerium oxide were realized, first as an active catalytic component of the TWC and subsequently as a catalyst and sorbent in various industrial applications. A review article by Trovarelli on ceria-based catalysts is a good recent compilation.
Patent•
30 Mar 2001
TL;DR: In this paper, a corrosion resistant component of semiconductor processing equipment such as a plasma chamber comprises a cerium oxide containing ceramic material as an outermost surface of the component, and one or more intermediate layers may be provided between the component and the cerium oxides containing ceramic coating.
Abstract: A corrosion resistant component of semiconductor processing equipment such as a plasma chamber comprises a cerium oxide containing ceramic material as an outermost surface of the component. The cerium oxide containing ceramic material comprises one or more cerium oxides as the single largest constituent thereof. The component can be made entirely of the cerium oxide containing ceramic material or, alternatively, the cerium oxide containing ceramic can be provided as a layer on a substrate such as aluminum or an aluminum alloy, a ceramic material, stainless steel, or a refractory metal. The cerium oxide containing ceramic layer can be provided as a coating by a technique such as plasma spraying. One or more intermediate layers may be provided between the component and the cerium oxide containing ceramic coating. To promote adhesion of the cerium oxide containing ceramic coating, the component surface or the intermediate layer surface may be subjected to a surface roughening treatment prior to depositing the cerium oxide containing ceramic coating.
Patent•
18 Dec 2001TL;DR: In this paper, the authors proposed a method to obtain a pore volume of from about 0.5 to about 2.0 cc/g, with a surface area of between 80 and 350 m2/g and an average pore size diameter of between about 3 to 30 nm.
Abstract: The lean NOx catalyst includes a substrate, an oxide support material, preferably γ-alumina deposited on the substrate and a metal or metal oxide promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium cerium, and vanadium, and oxides thereof, and any combinations thereof. The γ-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between 80 and 350 m2/g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to about 0.2 weight percent. In a preferred embodiment the γ-alumina is prepared by a sol-gel method, with the metal doping of the γ-alumina preferably accomplished using an incipient wetness impregnation technique.
TL;DR: In this article, the thermodynamic and kinetic properties of solutions of lanthanide (lanthanum, cerium, praseodymium, gadolinium) and yttrium chlorides in fused alkali chlorides were obtained from transient electrochemical techniques.
Abstract: The thermodynamic and kinetic properties of solutions of lanthanide (lanthanum, cerium, praseodymium, gadolinium) and yttrium chlorides in fused alkali chlorides were obtained from transient electrochemical techniques. Digital simulation was used to obtain a precise analysis of transient responses including perturbing factors such as ohmic drop, electrocrystallization, and reduction of alkali ions. A fitting procedure, included in the numerical calculation, allows an accurate determination of reaction parameters, diffusion coefficients, standard potentials, and covering factor. The technique was extended to the formation of lanthanum and gadolinium alloys with nickel.
TL;DR: In this paper, the solubilities of the cerium(IV), terbium(III), and iron(III) chelates of the anions of 2,2,7-trimethyl-3,5-octanedionate, H(tod), 2.2,6,6-tetramethyl- 3,5-, H(thd), and 2,4-pentanedionates, H (acac), were measured in supercritical carbon dioxide by near-infrared spectroscopy from 313 to 333 K and 10
Abstract: The solubilities of the cerium(IV), terbium(III), and iron(III) chelates of the anions of 2,2,7-trimethyl-3,5-octanedionate, H(tod), 2,2,6,6-tetramethyl-3,5-octanedionate, H(thd), and 2,4-pentanedionate, H(acac), were measured in supercritical carbon dioxide by near-infrared spectroscopy from 313 to 333 K and 10 to 35 MPa with a high-pressure optical cell. Solubilities increased in the order acac < thd < tod for all metal β-diketonates, with Ce(tod)4, Tb(tod)3, and Fe(tod)3 an order of magnitude more soluble than Ce(thd)4, Tb(thd)3, and Fe(acac)3, respectively. For the larger metal ions, Ce4+ and Tb3+, the flexibility of the isobutyl group in the tod ligand creates a more lipophilic shell around the central metal ion, increasing the solubility of the chelate in CO2. These observations indicate that the isobutyl group is at least as CO2-philic as the tert-butyl moiety. The experimental solubilities were correlated using the model proposed by Chrastil.
TL;DR: In this paper, the authors investigated the diffusion of both cerium and oxygen ions by TPSSIMS and obtained low-energy electron diffraction patterns and Auger electron spectroscopy spectra free of impurity signals.
Abstract: Ceria (CeO2) is an oxygen storage material vital to the proper functioning of automobile three-way catalysts and is typically viewed as an anion conductor. Prior experimental work using temperature programmed static secondary ion mass spectrometry (TPSSIMS) has indicated that for rutile TiO2, a prototypical oxide, the mobile species are Ti cations rather than O anions. To further expand on the mobile species in CeO2 we have investigated the diffusion of both cerium and oxygen ions by TPSSIMS. The CeO2(111) film was heteroepitaxially grown by molecular beam epitaxy on a yttria stabilized zirconia substrate. Although high quality low-energy electron diffraction patterns and Auger electron spectroscopy spectra free of impurity signals were obtained after just a few sputtering and annealing cycles, further cleaning was necessary to remove intense alkali and alkaline earth signals observed in SSIMS. The CeO2(111) surface was slightly enriched in 18O by first annealing the film in UHV at 830 K and then exposing...
TL;DR: In this article, ternary yttrium-based alloys belonging to the R-Y-Ni system (R=La, Ce), with general formula La1−xCexY2Ni9 (0≤x≤1) have been synthesized, and their hydrogen absorption-desorption properties have been investigated through solid gas and electrochemical measurements.
TL;DR: In this article, a low coordination ODH active site is proposed to involve an anionic vacancy common to two cations of different natures, XM−YM' (where X and Y are the numbers of unsaturation of each cation), allowing a heterolytic abstraction of a H- species from the alkane while the H+ species leads with the O2- species of the so...
Abstract: The oxidative dehydrogenation (ODH) of propane has been studied on cerium-based mixed oxides. An optimum propene yield of 5.4% is obtained at a low temperature (648 K) on CeNi0.5OY, and this yield can be increased to 6.9% by treating the solid in situ under H2. In situ “under catalytic reaction” X-ray photoelectron spectroscopy evidences that the active Ni species present the characteristic of being able to be reduced and reoxidized easily and reversibly, allowed by their close interaction with Ce species. Moreover, the results obtained by X-ray diffraction analysis performed after a catalytic test are in agreement with the presence of hydrogen species in the anionic vacancies of the solid. So, a low coordination ODH active site is proposed to involve an anionic vacancy common to two cations of different natures, XM−YM‘ (where X and Y are the numbers of unsaturation of each cation), allowing a heterolytic abstraction of a H- species from the alkane while the H+ species leads with the O2- species of the so...
Patent•
6 Mar 2001
TL;DR: A high transmission flat glass, which has a chemical composition, wherein the glass contains, as coloring components, in wt %, 0.005 % or more and less than 0.02 % of total iron oxides in terms of Fe2O3, less than0.008 % of FeO and 0 to 0.25 % of cerium oxides, and exhibits a high transmittance for visible lights and solar radiation rays, and when irradiated with an ultraviolet ray having a wavelength of 335 nm, a ratio of a fluorescent strength at 395 nm to that
Abstract: A high transmission flat glass, which has a chemical composition, wherein the glass contains, as coloring components, in wt %, 0.005 % or more and less than 0.02 % of total iron oxides in terms of Fe2O3, less than 0.008 % of FeO and 0 to 0.25 % of cerium oxides, and the proportion of FeO in terms of Fe2O3 to total iron oxide is 40 % or less, and exhibits a high transmittance for visible lights and solar radiation rays; or a high transmission flat glass, which comprises 0.06 % or less of total iron oxides and 0.025 to 0.20 % of cerium oxide, and exhibits, when irradiated with an ultraviolet ray having a wavelength of 335 nm, a ratio of a fluorescent strength at 395 nm to that at 600 nm of 10 % or more.
TL;DR: In this article, three electroanalytical techniques have been used to study the solid-state ionic diffusion of lithium into cerium-vanadium mixed oxide thin films, i.e., potentiostatic intermittent titration, galvanostatic and electrochemical impedance spectroscopy.
TL;DR: Tetraaryl-substituted cerium(IV) double-decker porphyrin (2D) was synthesized and their ring rotation rates were systematically estimated by means of a VT NMR spectroscopic method as mentioned in this paper.
Abstract: Tetraaryl-substituted cerium(IV) double-decker porphyrin (2D), tetraaryl-substituted lanthanum(III) double-decker porphyrin (3D), and diaryl-substituted lanthanum(III) triple-decker porphyrins (4T•Me and 4T•MeO) were newly synthesized and their porphyrin ring rotation rates were systematically estimated by means of a VT NMR spectroscopic method. In 2D the coalescence temperature (Tc) for the porphyrin ring rotation was higher than 110 °C, whereas in 3D it appeared at ca. 0 °C. In diaryl-substituted cerium(IV) double-decker porphyrin (5D) it appeared at 13 °C whereas in 4T•Me and 4T•MeO they were lower than −80 °C. These results consistently support the view that the porphyrin ring rotation rates in lanthanum(III)-based porphyrins are much faster than those in cerium(IV)-based porphyrins. The difference is reasonably explained by the difference in the ion size between these two metal ions. Since these sandwich-type porphyrins can act as novel scaffolds for designing positive allosteric recognition systems,...
TL;DR: In this article, the anodic corrosion of Pb-Ca-Sn alloy in 4.5 M H 2 SO 4 at 20°C was studied using cyclic voltammetry, linear sweep voltameters, ac voltametermetry, chronoamperometry, and scanning electron microscopy.
TL;DR: In this article, the capability of oxygen store and release of ceria-zirconia solid solution made by attrition mill process was measured by thermo-gravimeter with 1% of Pt.
Abstract: Capability of oxygen store and release of ceria-zirconia solid solution made by attrition mill process was measured by thermo-gravimeter with 1mass% of Pt. Ceria-zirconia solid solution made by conventional heating method of ceria powder with zirconium salt was also characterized for comparison. Capability of oxygen store and release of ceria-zirconia solid solution made by attrition mill process is about three times larger than that of conventionally made samples. And, the point, where zirconium content is 100% on the relation between capability of oxygen store and release and zirconia content in the ceria-zirconia solid solution, corresponds to the state in which the valence of all the cerium ion being contained in the solid solution is 3. This fact suggests that the mechanism, that the increase of capability of oxygen store and release by dissolving zirconia into ceria, is that zirconium ions, which are smaller than cerium ions of the valence 4, release the strain caused by the expansion due to a reduction of cerium ions.
TL;DR: The effect of a platinum metal additive on the performance of three commonly used base-metal fuel additives for the catalytic oxidation of diesel particulate was studied Engine experiments using Corning EX80 filters and oxidation experiments in flow-reactor equipment.
Abstract: The effect of a platinum metal additive on the performance of three commonly used base-metal fuel additives for the catalytic oxidation of diesel particulate was studied Engine experiments using Corning EX80 filters and oxidation experiments in flow-reactor equipment showed that especially a combination of platinum and cerium additives is very active in the catalytic oxidation of diesel particulates The additive dose rate can be very low, ie, about 5 ppm cerium and 025 ppm platinum, without loss of effectiveness NO2 plays a key role in this process Platinum accumulated on the filter catalyses the oxidation of NO to NO2, whereas cerium catalyses the oxidation of particulate with NO2 Copper and iron do not catalyse the latter reaction An additional effect of this oxidation mechanism is a substantial NO2 reduction