Cerium production

There are few principal lanthanide deposits, and there are no minerals that are sources for cerium alone. All the lighter lanthanides occur together in any potential deposit, and processes separating the lanthanides are necessary to obtain pure cerium products. 

To observe a solid solution from the L2S3 sulfides it is necessary to prepare the products at high enough temperatures (about 1300° C. for lanthanum and cerium products) and to quench them quickly. At the lower temperatures, the solid solution does not begin at but further on, because the rare earth sulfides have other polymorphic forms in the equilibrium conditions, and because these other forms, a and / , do not dissolve the MS sulfides. 

Cerium oxide is the most efficient polishing agent for most glass compositions [23]. This application consumes a significant portion of the cerium products produced annually. 

A large deposit of loparite occurs ia the Kola Peninsula, Russia. The production of REO reaches 6500 t/yr. Loparite contains over 30% of rare-earth oxides from the cerium group. In addition, loparite contains up to 40% titanium oxide and up to 12% niobium and tantalum oxides. 

Separation Processes. The product of ore digestion contains the rare earths in the same ratio as that in which they were originally present in the ore, with few exceptions, because of the similarity in chemical properties. The various processes for separating individual rare earth from naturally occurring rare-earth mixtures essentially utilize small differences in acidity resulting from the decrease in ionic radius from lanthanum to lutetium. The acidity differences influence the solubiUties of salts, the hydrolysis of cations, and the formation of complex species so as to allow separation by fractional crystallization, fractional precipitation, ion exchange, and solvent extraction. In addition, the existence of tetravalent and divalent species for cerium and europium, respectively, is useful because the chemical behavior of these ions is markedly different from that of the trivalent species. 

Bastnasite has been identified in various locations on several continents. The largest recognized deposit occurs mixed with monazite and iron ores in a complex mineralization at Baiyunebo in Inner MongoHa, China. The mineral is obtained as a by-product of the iron ore mining. The other commercially viable bastnasite source is the Mountain Pass, California deposit where the average Ln oxide content of the ore is ca 9%. This U.S. deposit is the only resource in the world that is minded solely for its content of cerium and other lanthanides. 

The production of cerium derivatives begins with ore beneficiation and production of a mineral concentrate. Attack on that concentrate to create a suitable mixed lanthanide precursor for later separation processes follows. Then, depending on the relative market demand for different products, there is either direct production of a cerium-rich material, or separation of the mixed lanthanide precursor into individual pure lanthanide compounds including compounds of pure cerium, or both. The starting mineral determines how the suitable mixed lanthanide precursor is formed. In contrast the separation... 

An alternative process for opening bastnasite is used ia Chiaa high temperature roastiag with sulfuric acid followed by an aqueous leach produces a solution containing the Ln elements. Ln is then precipitated by addition of sodium chloride as a mixed sulfate. Controlled precipitation of hydroxide can remove impurities and the Ln content is eventually taken up ia HCl. The initial cerium-containing product, oace the heavy metals Sm and beyond have been removed, is a light lanthanide (La, Ce, Pr, and Nd) rare-earth chloride. 

Production of Cerium Derivatives. Moderately pure (90—95%) cerium compounds can be made from rare-earth chloride through oxidation with, for example, hypochlorite to produce an iasoluble cerium hydrate. The other lanthanides remain ia solutioa. The hydrate, oa calciaatioa, coaverts to Ce02. 

The purity of the cerium-containing materials depends on the appHcation as indicated in Table 3, and purity can mean not only percentage of cerium content but also absence of unwanted components. For some uses, eg, gasoline production catalysts, the lanthanides are often used in the natural-ratio without separation and source Hterature for these appHcations often does not explicitly mention cerium. Conversely, particulady in ferrous metallurgy, cerium is often assumed to be synonymous with rare-earth or lanthanide and these terms are used somewhat interchangeably. 

Another process for the production of dodecanedioic acid is by oxidation of cyclododecene using a two-phase system in which mthenium tetroxide serves as the oxidizing agent in the organic phase, and is regenerated in the second phase, an aqueous phase containing cerium(IV) ions (75). 

Carbochem - Supplies carbon and other chemical products based in copper, cerium, nickel, and cobalt. http //www.carbochem.com. 

Consider file fission reaction in which U-235 is bombarded by neutrons. The products of the bombardment are rubidium-89, cerium-144, beta particles, and more neutrons. 

The addition of a phenylcerium reagent 0 PhCeCl, ) in tctrahydrofuran to the pyrazoline 4 at — 78 C using an equimolar ratio of cerium(III) chloride, phenyllithium and pyrazoline (CcCI3/ Cf,H,I-i/4 1 1 1) exclusively provides the desired pyrazolidine 5 in good yields (75-94%). This product can be converted to the diamine 3a (R = H) and subsequently into numerous N-sub-stituted derivatives of 3a (e.g.. 3b R = CH3) by means of simple standard procedures23. 

Magnesium salts have long been employed for this purpose because MgO has a melting point of over 5000 °F (approximately 5070 °F/2800 °C) and forms complex salts with elements, such as vanadium, that have MPs of between 1500 and 2500 °F. Cerium salts generally are used in superior products, however, because they are much more efficient than magnesium (perhaps 3-5 times more efficient), but they also are much more expensive. 

A number of electrolytic processes are used for the industrial production of metals. Some metals such as zinc, copper, manganese, gallium, chromium, etc. are electrowon from aqueous baths. Another common electrolytic process used is molten salt electrolysis. The most important application of molten salt electrolysis till now has been in the electrowinning of metals. Today aluminum, magnesium, lithium, sodium, calcium, boron, cerium, tantalum, and mischmetal are produced in tonnage quantities by molten salt electrolysis. As a representative example, the electrowinning process for aluminum is taken up. 

Cationic polymerization of alkenes and alkene derivatives has been carried out frequently in aqueous media.107 On the other hand, the reaction of simple olefins with aldehydes in the presence of an acid catalyst is referred to as the Prins reaction.108 The reaction can be carried out by using an aqueous solution of the aldehyde, often resulting in a mixture of carbon-carbon bond formation products.109 Recently, Li and co-workers reported a direct formation of tetrahydropyranol derivatives in water using a cerium-salt catalyzed cyclization in aqueous ionic liquids (Eq. 3.24).110... 

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