Chemical composition cerium oxide

Cerium also has minor uses in other commercial catalysts [17]. The dominant catalyst for the production of styrene from ethylbenzene is an alkali-promoted iron-oxide based material. The addition of a few percent of cerium oxide to this system improves activity for styrene formation. The ammoxidation of propylene to produce acrylonitrile is carried out over catalytically active complex molybdates. Cerium, a component of several patented compositions [18], supports the chemical reaction. 

The chemical composition of imported, European-made majolica is different from that of majolica made in Mexico (J). The difiFerences in the concentrations of the oxides of cerium, lanthanum, and thorium are eaily recognized the Spanish majolica contains approximately twice as much of each of these oxides as the Mexican majolica. The mineralogical composition, too, of the pottery products of each area is fundamentally different and can easily be identified. The ceramic types and their origins, based on archaeological arguments, can be found in Table I. 

The chemical composition of the washcoat belongs to the core know-how of the catalyst manufacturers. The most common washcoats contain aluminum oxides, cerium oxides and zirconium oxides as major constituents. The minor constituents... 

The samples studied herein are a 99.9% pure cerium dioxide (sample C) prepared as described elsewhere [15,16], a pure terhia showing a conq>osition IbOuez (sample T), and a ceiia/terbia mixed oxide with 20 mole percent of terbia (CH -80/20), finm our laboratory. In this latter case, the nominal chemical composition was fiirther confirmed by ICP analysis of a series d previously dissolved oxide samples. 

One category of dense proton conducting membranes that has received considerable attention in the preceding decade is proton conducting perovskite type oxide ceramics [4-6]. The stoichiometric chemical composition of perovskites is represented as ABO3, where A is a divalent ion (A +) such as calcium, magnesium, barium or strontium and B is a tetravalent ion (B +) such as cerium or zirconium. Although simple perovskites such as barium cerate (BaCeOs) and strontium cerate... 

B2.1 The system for identifying the electrode classifications in this specification follows the standard pattern used in other AWS filler metal specifications. The letter E at the beginning of the classification designation stands for electrode. The W indicates that the electrode is primarily tungsten. The F indicates that the electrode is essentially pure tungsten and contains no intentionally added emission enhancing elements. The Ce, La, Th, and Zr indicate that the electrode is doped with oxides of cerium, lanthanum, thorium, or zirconium, respectively. The numeral at the end of some of the classifications indicates a different chemical composition level or product within a specific group. 

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

Cerium, praseodymium, and terbium oxides display homologous series of ordered phases of narrow composition range, disordered phases of wide composition range, and the phenomenon of chemical hysteresis among phases which are structurally related to the fluorite-type dioxides. Hence they must play an essential role in the satisfactory development of a comprehensive theory of the solid state. All the actinide elements form fluorite-related oxides, and the trend from ThOx to CmOx is toward behavior similar to that of the lanthanides already mentioned. The relationships among all these fluorite-related oxides must be recognized and clarified to provide the broad base on which a satisfactory theory can be built. 

Catalysts for the chemical industry have to be characterized with respect to their trace impurities and major components. Not only is their composition when they are used initially in chemical reactors important, but also their alteration in the course of time. As carbide forming elements such as V and Ti are often used, atomic absorption spectrometry could be problematic. This also applies to catalysts for exhaust gas detoxification in cars. Noble metals such as Pt, Pd and Rh are fixed on alumina supports often also containing cerium compounds. Both for the determination of the stoichiometry but also for the monitoring of the noble metal contents in used catalysts, AAS suffers from problems because of the need for sample dissolution as well as for the requirement to determine refractory oxide forming elements. 

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