Alkaline earth metal oxides deposition

A.l. Alkaline Earth Metal Oxides Doped with Alkali Metals by Chemical Vapor Deposition... 

Other alkaline earth metal oxides and related Group II metal oxides were screened for activity. Tests indicated that magnesia-zinc oxide combinations were about as efficient as magnesia alone. Calcium oxide, zinc oxide, and cadmium oxide were all catalysts for the reaction but were not as effective as magnesium oxide. Efficiencies of these oxides were increased by supporting them on activated alumina. In addition, it was found that sodium and lithium compounds deposited on activated alumina were active cat-... 

A Basicity of Alkali Metal Ion-doped Oxides.- In order to increase a surface basicity, different species with donor properties may be deposited. The majority of these are the alkali metal salts or salts of the alkaline earth metals. The deposition of hydroxides carbonates, nitrates, oxalates and other organic salts of L,i, Na, K, Rb, Cs, Mg, Ca, Sr, Ba on different supports has been known for years. They are said to increase the basic properties of the surface. The mechanism of the creation of these new basic centres is not clear, because the acid-base properties of a support, on which the salt has been introduced, do not change monotonically with the quantity of introduced metal ions. It is possible, that the interaction of surface groups with the metal ions leads to several reactions,... 

Panov, V.l. and Petrov, V.A., Electrophoretic deposition of suspensions of alkaline-earth metal oxides. Sov. J. Colloid. Sci. 359-62 (1975). 

Apart from the primary purposes of tying up alkaline earth metals to reduce waterside fouling and solubilizing old, formed deposits, formu-lators have also long used chelants because of their buffering, product stability, and oxidation-reduction control effects. 

The alkali metals (Group 1A) and the alkaline earth metals (Group 2A) are not found free in nature because they are so easily oxidized. Their primary sources are seawater, brines of their soluble salts and deposits of sea salt. The metals are obtained from the electrolysis of their molten salts. 

The colloidal particles are often deposited on metallic electrodes in the form of adsorbed coatings. Rubber and graphite coatings can be formed in this way, using solvent mixtures (water-acetone) as the dispersion media. The advantage of this method is that additives can firmly be codeposited with, for example, rubber latex. Thermionic emitters for radio valves are produced in a similar manner. The colloidal suspensions of alkaline earth carbonates are deposited electrophoretically on the electrode and are later converted to oxides by using an ignition process. 

U is also found in the Soviet Union where there are sources in Karelia, near Dnepropetrovsk, the Kirghiz Soviet Republic and in Transcaucasia Whereas once U ores were processed for their Ra content, Ra has now lost its commercial importance and it is considered a contaminant. Only two U ores have been processed extensively, pitchblende and carnotite. The general procedure is to solubilize the U with an acid, convert the ion to a complex carbonate (thereby removing the Fe, A1 and Mn), ppt the Pb and Cu as the sulfide, and finally, to recover the U as the ammonium uranate and hence, as the oxide U metal can be obtained from the oxide or the halide by reduction with alkali metals or alkaline earth metals. U, being highly electropositive, cannot be deposited electrolytically from aq solns. Thermal decompn of the tetra-iodide is possible (Ref 1)... 

Clays are natural compounds of silica and alumina, containing major amounts of the oxides of sodium, potassium, magnesium, calcium, and other alkali and alkaline earth metals. Iron and other transition metals are often found in natural clays, substituted for the aluminum cations. Oxides of virtually every metal are found as impurity deposits in clay minerals. 

The deposition of alkaline-earth-metal atoms and ozone molecules at high dilution in argon at 15 K yields species showing intense bands in the i.r. at 800 and 450—650 cm-1. Those at 800 cm"1 showed the appropriate isotopic shifts for assignment of v3 for the ozonide ion, Oj. The use of scrambled isotopic ozones indicates that the metal cation is symmetrically bound to the ozonide ion, which contains three O atoms, with two of these equivalent. In addition, calcium and barium mixtures with ozone contain several metal oxide species tentatively identified as (CaO)2, Ca02,BaO, and (BaO)2, respectively.73... 

We have recently suggested a new approach to the preparation of active sites in sulfated zirconia catalysts [5, 6]. In this case, the catalysts are prepared by deposition of sulfate ions on crystalline zirconium dioxide samples with highly defective structure. According to numerous reports, the monoclinic phase typical for ZrOa is not suitable for this purpose. We have shown that active materials could be obtained by impregnation of zirconia-based oxides with cubic crystalline structure. It should be noted that the cubic structure is not thermodynamically stable for pure zirconia at low temperatures. It can be stabilized by introducing different additives, in particular, alkaline-earth metal cations [7]. Recently, similar results have been obtained for ZrOa stabilized by Y2O3 [8]. 

The main cause of deactivation are elements or compounds which chemically attack the catalytically active material or its support. Also, structural changes and pore blocking are important issues of deactivation. A variety of poison compounds containing elements such as halogens, alkah metals, alkaline earth metals, arsenic, lead, phosphorus, and sulfur are mentioned in the hterature. AS2O3 is the most severe poison in coal-fired power plant operation in Germany. In power plants equipped with wet-bottom boilers alkah metal oxides mostly remain in the molten ash, whereas AS2O3 tends to escape into the flue gas and deposits on the catalyst. 

Other supports with different acidic characteristics and the addition of alkali or alkaline-earth metals and other promoters are used [2, 3]. For example, the addition of tin (Sn), which affects the amount of the oxidized chromium, results in a significant decrease of the amount of deposited coke. The Sn addition also improves selectivity, but, unfortunately, reduces catalytic activity [3]. Alternative catalysts are extensively investigated and some of them are already in commercial use (e.g., Pt-based). 

The elements from lanthanum (Z = 57) through lutetium (Z = 71) are variously called the lanthanide, lanthanoid, or rare earth elements. The rare earth elements are "rare" only relative to the alkaline earth metals (group 2). Otherwise, they are not particularly rare. Ce, Nd, and La, for example, are more abundant than lead, and Tm is about as abundant as iodine. The lanthanides occur primarily as oxides, and mineral deposits containing them are found in various locations. Large deposits near the California-Nevada border are being developed to provide oxides of the lanthanides for use as phosphors in color monitors and television sets. 

Deposits also contain non-volatile residuals that constitute the ash. These include alkali and alkaline earth metals, together with the constituents of silts and clays that commonly occur in sedimentary rocks (Si, A1 and Fe present as oxides, hydroxides, carbonates). 

Compressed oxygen, and fresh and recycled ethylene, are heated, mixed, and then passed through a reactor with fixed beds of catalyst— silver oxide deposited on alumina pellets. In recent years the catalyst has been improved by the addition of promoters and inhibitors. (Promoters—in this case compounds of alkali or alkaline rare earth metals—enhance the activity of the catalyst inhibitors—in this case chlorine compounds—chloroethane, or vinyl chloride, reduce its rate of activity decline.)... 

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