Water cerium oxide

Hydroxide. Freshly precipitated cerous hydroxide [15785-09-8] Ce(OH)2, is readily oxidized by air or oxygenated water, through poorly defined violet-tinged mixed valence intermediates, to the tetravalent buff colored ceric hydroxide [12014-56-17, Ce(OH)4. The precipitate, which can prove difficult to filter, is amorphous and on drying converts to hydrated ceric oxide, Ce02 2H20. This commercial material, cerium hydrate [23322-64-7] behaves essentially as a reactive cerium oxide. 

Nitrate. Cerium(III) nitrate hexahydrate [10294-41 -4] Ce(N03) 6H20, is a commercially available soluble salt of cerium, and because of ready decomposition to the oxide, it is used, for example, when a porous sohd is to be impregnated with cerium oxide. The nitrate is very soluble in water, up to about 65 wt %. It is also soluble in a wide range of polar organic solvents such as ketones, alcohols, and ethers. 

In addition to platinum and related metals, the principal active component ia the multiflmctioaal systems is cerium oxide. Each catalytic coaverter coataias 50—100 g of finely divided ceria dispersed within the washcoat. Elucidatioa of the detailed behavior of cerium is difficult and compHcated by the presence of other additives, eg, lanthanum oxide, that perform related functions. Ceria acts as a stabilizer for the high surface area alumina, as a promoter of the water gas shift reaction, as an oxygen storage component, and as an enhancer of the NO reduction capability of rhodium. 

Cerium oxides are outstanding oxide materials for catalytic purposes, and they are used in many catalytic applications, for example, for the oxidation of CO, the removal of SOx from fluid catalytic cracking flue gases, the water gas shift reaction, or in the oxidative coupling reaction of methane [155, 156]. Ceria is also widely used as an active component in the three-way catalyst for automotive exhaust pollution control,... 

Fu Q, Deng W, Saltsburg H, Flytzani-Stephanopoulos M (2005) Activity and stability of low-content gold-cerium oxide catalysts for the water-gas shift reaction. Appl Catal B 56 57-68... 

Li, Y., Fu, Q., and Flytzani-Stephanopoulos, M. 2000. Low-temperature water-gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts. Appl. Catal. B Environ. 27 179-91. 

Cerium sulfide pigments are produced from hydrated cerium oxide or oxalate and calcined in an oxygen-free, sulfide environment. They are silica-encapsulated to minimize water-reactivity and to improve heat stability and chemical resistance properties. Because of their low relative value-in-use, they are used primarily in engineering plastics and in particular the polyamides where high-performance organic colorant alternatives and other inorganic pigment alternatives are few. 

Cerium (IV) ammonium nitrate (CAN) [NH4]2[Ce(N03)6], is a water-soluble oxidant, classical in organic chemistry [197], which has sometimes been used in or-ganometallic chemistry to disengage ligands from metal centers [211]. It can be used... 

Using small quantities of additives, such as cerium oxide, incorporated in the fuel or injected into the exhaust ahead of the particulate trap. The additive, when collected on the filter with the particulate, allows the particulate to bum at normal exhaust temperatures to form carbon dioxide and water. This system is insensitive to sulphur and can be used with current European diesel fuel containing 500 PPM of sulphur. 

The hydrothermal method composes of three types of processes hydrothermal synthesis, hydrothermal oxidation, and hydrothermal crystallization. Hydrothermal synthesis is usually used to synthesize oxides from their component salts, oxides or hydroxides. Pressures, temperatures, and mineralizer concentrations control the size and morphology of the particles. Forced hydrolysis of solutions of a rare earth salt is effective to obtain uniform and fine particles. For example, cerium oxide fine particles were prepared from tetravalent cerium salt solution (CeS04-4H20, (NH4)4Ce(S04)4 2H20, and (NH4)2Ce(N03)6) in low concentrations by low temperature aging in a sealed vessel (see Fig. 6-4) [38-41]. The metal ions are solvated by water molecules which can be deprotonated to give hydroxide or oxide particles. This method is very sensitive to the concentration, temperature, and pH value of the solution. 

The size of the nanodroplets can be controlled in the range of 5 - 80 nm by changing the concentration ratio of water/surfactant in the microemulsion system. By this method, yttrium oxide [67], cerium oxide [68-70], neodymium oxide [71], and erbium oxide [72, 73] nanoparticles have been synthesized. The average particle size of the particles adopts values in the range fi om 2 to 70 nm, which depends on the synthesis conditions. 

Cerium oxide is of major importance in the glass industry because of its ability to polish glass, thanks to its natural hardness and to the chemical reaction [24, 25] that takes place at the interface between the glass silica substrate and the cerium oxide particles. This reaction occurs in water and involves the creation of a silicate stratum which makes the glass surface more fragile and less resistant to mechanical erosion and physical modifications. 

Ceria is an easily reducible oxide, and any redox pretreatment strongly affects the nature of the surface hydroxyl groups. Cerium oxide has been the subject of detailed DFT calculations, and the results were recendy summarized (69 f). It was noted that H2O molecules strongly and dissociatively bind on oxygen vacancy sites and the dissociative adsorption of water is favored on defective surfaces. Even at low temperature, water dissociates on partially reduced ceria (692). It was reported that surface hydroxyls on ceria are also produced as a result of H2 dissociation (509). 

Y. Wang, S. Lianga, A. Caoa, R. L. Thompson, G. Vesera, Au-mixed lanthanum/cerium oxide catalysts for water gas shift, Appl. Catal. B Environ. 99 (2010) 89-95. 

Earlier studies made Mosander suspect that cerium oxide obtained from cerite contains a foreign substance. He attempted to separate it by shaking cerium oxide hydrate with water, introducing chlorine gas to transform cerium oxydul into cerium oxide and the unknown substance into chlorure. Insoluble yellow cerium oxide was precipitated in the operation. From the filtrate he again precipitated the solute with potassium hydrate, shook the suspension and again introduced chlorine gas. Further cerium oxide was precipitated and the rest was dissolved. He repeated this operation several times, in this manner he succeeded to separate the total amount of cerium oxide and obtain a chlorure from which potassium hydrate precipitated a hydrate that did not turn yellow in air and when treated with chlorine, was completely soluble in water. Thus the separation was terminated, and the oxide which is not further oxidized by chlorine gas was termed lanthanum oxide, as generally known. 

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