C-rare earth oxide

Tsang SC, Bulpitt C. Rare earth oxide sensors for ethanol analysis. Sens. Actuators, B Chemical. 1998 52 226-235. DOI 10.1016/S0925-4005(98)00233-0. 

Re OPe . The final step in the chemical processing of rare earths depends on the intended use of the product. Rare-earth chlorides, usually electrolytically reduced to the metallic form for use in metallurgy, are obtained by crystallisation of aqueous chloride solutions. Rare-earth fluorides, used for electrolytic or metaHothermic reduction, are obtained by precipitation with hydrofluoric acid. Rare-earth oxides are obtained by firing hydroxides, carbonates or oxalates, first precipitated from the aqueous solution, at 900°C. 

We also see (Fig. 6) that raising the calcination temperature of rare earth modified silica-aluminas from 500 to 600°C, may slightly sinter the rare earth oxide. Although the x-ray pattern... 

We measured the dispersion of Pt (impregnated from a chloroplatinic acid precursor, calcined at 450 C and reduced at 500 C) on a series of Nd203-loaded silica-aluminas (Fig. 8). We find, unexpectedly, that dispersion increases with increasing rare earth oxide loading up to about 18% Nd203, where it plateaus at between 40 and 50%, compared to 10% with unmodified Si-Al. This compares with dispersions of -60-80% measured on similarly Pt-loaded transitional AI2O3 catalysts. Transmission electron micrographs confirmed the decrease in particle size with rare earth content on Si-Al. 

The hydrofluorination of rare earth oxides with ammonium bifluoride is carried out as a batch process by heating the rare earth oxide with 30% excess of high-purity NH4F HF in a platinum boat inside an inconel chamber at 300 °C under a stream of dry air. 

Table 8.9. NO dissociation over reduced rare-earth oxides and over 1% Pt catalysts deposited on these oxides. Gas Prior to NO dissociation (970 ppm NO), the samples are reduced for 1 h in H2 at 500°C [86]...

The rare earth oxides of lanthanum, samarium and gadolinium were converted into soluble nitrate salts by dissolving them in the minimum amount of concentrated nitric acid. Then two sets were prepared by adding 2.0 ml of aqueous solution of La(N03)3.6H20 [0.2 M] and 0.01 ml of (n-BuO)4Ti to 25 ml of aqueous solution of Cu(N03)2 [1.0 M]. Similarly, two sets were prepared with Co(N03)3. Same procedures were followed for Sm(N03)3 [0.2 M] and Gd(N03)3 [0.2 M], One set of all these solutions were sonicated under ultrasonic bath (Model - Meltronics, 20 kHz, 250 W) for half an hour. The solutions prepared in normal and sonicated conditions were kept in muffle furnace (Model - Deluxe Zenith) first at 100°C for 2 h and then the temperature of the furnace was raised up to 900°C and calcined for 2 h. The solid composites prepared were then cooled to room temperature and treated as catalyst for phenol degradation. 

IR spectrometers have the same components as UY/visible, except the materials need to be specially selected for their transmission properties in the IR (e.g., NaCl prisms for the monochromators). The radiation source is simply an inert substance heated to about 1500 °C (e.g., the Nernst glower, which uses a cylinder composed of rare earth oxides). Detection is usually by a thermal detector, such as a simple thermocouple, or some similar device. Two-beam system instruments often work on the null principle, in which the power of the reference beam is mechanically attenuated by the gradual insertion of a wedge-shaped absorber inserted into the beam, until it matches the power in the sample beam. In a simple ( flatbed ) system with a chart recorder, the movement of the mechanical attenuator is directly linked to the chart recorder. The output spectrum is essentially a record of the degree of... 

S. J. Choqnette, J.C. Travis, L.E. O Neal, C. Zhn, and D.L. Dnewer, SRM 2035 a rare earth oxide glass for the wavelength calibration of near infrared dispersive and Fonrier transform spectrometers. Spectroscopy, 16(4), 14—19... 

Gadolinium is produced from both its ores, monazite and bastnasite. After the initial steps of crushing and beneficiation, rare earths in the form of oxides are attacked by sulfuric or hydrochloric acid. Insoluble rare earth oxides are converted into soluble sulfates or chlorides. When produced from monazite sand, the mixture of sand and sulfuric acid is initially heated at 150°C in cast iron vessels. Exothermic reaction sustains the temperature at about 200 to 250°C. The reaction mixture is cooled and treated with cold water to dissolve rare earth sulfates. The solution is then treated with sodium pyrophosphate to precipitate thorium. Cerium is removed next. Treatment with caustic soda solution fohowed by air drying converts the metal to cerium(lV) hydroxide. Treatment with hydrochloric or nitric acid sol-... 

Insoluble silica residues are removed by filtration. The solution now contains beryllium, iron, yttrium, and the rare earths. The solution is treated with oxalic acid to precipitate yttrium and the rare earths. The precipitate is calcined at 800°C to form rare earth oxides. The oxide mixture is dissolved in an acid from which yttrium and the rare earths are separated by the ion-exchange as above. Caustic fusion may be carried out instead of acid digestion to open the ore. Under this condition sihca converts to sodium sihcate and is leached with water. The insoluble residue containing rare earths and yttrium is dissolved in an acid. The acid solution is fed to an ion exchange system for separating thuhum from other rare earths. 

Rare-earth oxides (La2C>3, Dy203) have been shown to be active in isosynthesis.283 284 It was also observed that zirconia may catalyze the highly selective formation of isobutylene under appropriate conditions.285 Two chain growth processes, CO insertion into aldehydic Zr-C bonds and condensation between methoxide and... 

The separation of rare earth oxides at 2500° C in a Solar furnace has been attempted [48], and Ce4+-oxide was obtained in a pure state from its mixture with lanthanum oxide. 

The anhydrous acetates of the rare earths have recently been prepared. Moeller et al. [355] obtained them for La, Dy, Ho, Er, Yb and Y by the azeotropic distillation of a mixture of hydrated acetates with N,N -dimethylformamide (DMF) and benzene. In the case of Ce, Pr, Nd, Sm, Eu and Gd the same method gave a monosolvated acetate, M(C2Hs02)3 DMF. However, the anhydrous acetates of Ce, Pr, Nd, Sm, Eu and Gd can be prepared [355] by vacuum desolvation of the monosolvated compounds. A direct desolvation of the acetates in vacuum at —150° C was attempted by Witt and Onstott [389] after dissolution of the rare earth oxides in 50 per cent acetic acid, and anhydrous acetates of definite composition were obtained for La, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu and Y. 

The ceramic properties of EU2O3 were investigated by Curtis and Tharp [305]. The electric conductivities of rare earth oxides including EU2O3 between 600—1300° C were reported [675]. The selective oxidation of Ci to C5 olefins and Ci to C5 alcohols by direct fuel cells employing noble metal anodes and aqueous H2SO4 electrolytes was found to be enhanced [676] by small additions of soluble salts of Ce, Eu and Yb. 

C.A. Arrhenius, in 1787, noted an unusual black mineral in a quarry near Ytterby. Sweden, This was identified later as containing yttrium and rare-earth oxides. With the exception of promethium, all members of the Lanthanide Series had been discovered by 1907, when lutetium was isolated. In 1947. scientists at the Atomic Energy Commission at Oak Ridge National Laboratory (Tennessee) produced atomic number 61 from uranium fission products and named it promethium. No stable isotopes of promethium have been found in the earth s crust. 

The method20 consists essentially of heating a mixture of rare earth oxides and excess ammonium chloride to a temperature of 200°C. or higher. Hydrolysis of the rare earth chlorides with formation of basic compounds is effectively prevented by the presence of excess ammonium chloride. The remaining ammonium chloride is then removed completely by heating in a vacuum at 300 to 320°C. 

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