Cerium sulfate oxidation

Ceri-oxyd, n. ceric oxide, cerium(IV) oxide, -salz, rt. ceric salt, cerium(IV) salt. sulfat, n. ceric sulfate, cerium(IV) sulfate. 

Cerium(IV) sulfate is prepared by heating cerium(IV) oxide, Ce02 with con-... 

Europeum generally is produced from two common rare earth minerals monazite, a rare earth-thorium orthophosphate, and bastnasite, a rare earth fluocarbonate. The ores are crushed and subjected to flotation. They are opened by sulfuric acid. Reaction with concentrated sulfuric acid at a temperature between 130 to 170°C converts thorium and the rare earths to their hydrous sulfates. The reaction is exothermic which raises the temperature to 250°C. The product sulfates are treated with cold water which dissolves the thorium and rare earth sulfates. The solution is then treated with sodium sulfate which precipitates rare earth elements by forming rare earth-sodium double salts. The precipitate is heated with sodium hydroxide to obtain rare earth hydrated oxides. Upon heating and drying, cerium hydrated oxide oxidizes to tetravalent ceric(lV) hydroxide. When the hydrated oxides are treated with hydrochloric acid or nitric acid, aU but Ce4+ salt dissolves in the acid. The insoluble Ce4+ salt is removed. 

It is of interest to compare the influence of cerium(III) on the cerium(IV)-ar-Cr(OH2)2(0204)2" reaction with the similar retarding action by cerium(III) which Tong and King (43) found in their careful kinetic investigation of the cerium(IV) oxidation of Cr(OH2)6+3 in acidic-sulfate media. The observed rate law for the latter reaction may be written in the form... 

Gasolines contain a small amount of sulfur which is emitted with the exhaust gas mainly as sulfur dioxide. On passing through the catalyst, the sulfur dioxide in exhaust gas is partially converted to sulfur trioxide which may react with the water vapor to form sulfuric acid (1,2) or with the support oxide to form aluminum sulfate and cerium sulfate (3-6). However, sulfur storage can also occur by the direct interaction of SO2 with both alumina and ceria (4,7). Studies of the oxidation of SO2 over supported noble metal catalysts indicate that Pt catalytically oxidizes more SO2 to SO3 than Rh (8,9) and that this reaction diminishes with increasing Rh content for Pt-Rh catalysts (10). Moreover, it was shown that heating platinum and rhodium catalysts in a SO2 and O2 mixture produces sulfate on the metals (11). 

The easily visualized Belousov Zhabotinsky (BZ) reaction is now a classic example of the emergence of temporal and spatio temporal dissipative struc tures in homogeneous chemical systems. The reaction was discovered by Soviet military chemist B. P. Belousov in 1951 when he was studying homo geneous oxidation of citric acid by potassium bromide, KBrOq, in the presence of cerium sulfate Ce(S04)2 as the catalyst for redox processes. In the dissolved mixture of these compounds under certain process conditions, Belousov discovered a time-oscillating synchronous reduction of cerium(4+) ions ... 

It is interesting to consider which factors are important in the formation of cerium sulfates. The presence or absence of Pt had little effect, showing that ceria is able to oxidize SO2 without an additional catalyst [42]. Furthermore, the oxidation of SO2 to S04 occurs on ceria to some extent without the addition of gas-phase O. obviously with the simultaneous reduction of ceria [40]. Finally, bulk sulfates were only formed when the ceria samples were exposed to SO2 at temperatures above 250"C. 

Tungsten hexafluoride, WF (mp 2.5 °C, bp 17 °C) [529], resembles M0F5 and M0OCI3 in its oxidative properties. However, less exotic reagents such as ozone, ammonium cerium sulfate, or zinc dichromate may be used for a similar purpose. 

Sodium bromate, NaBrOs, a white crystalline compound, converts acyloins into a-diketones under forcing conditions [740]. More often, this reagent is used as a reoxidant of ammonium cerium nitrate [421], cerium sulfate [741], or ruthenium trichloride [741] in oxidations of alcohols to aldehydes [421] or carboxylic acids [741]. 

Considerable interest has been shown in analytical methods for the determination of algin (68, 72, 78, 101, 158, 171, 21A, 292). Improvements were made in the Lefevre-Tollens hydrochloric acid decarboxylation method by McCready, Swenson, and Maclay (135, 143) to make it more adaptable to routine determinations. Kenyon and coworkers (148, 262, 271, 272) in a series of articles compared various methods for the determination of the carboxyl content of sugar acids. These included the calcium acetate-acetic acid method, the potentiometric titration method in the presence of sodium bromide, decarboxylation and determination of the isolated furfural. Percival and Ross (70, 187) described improvements in the colorimetric carbazole determination of algin. New analytical methods include the oxidation of algin with cerium sulfate (W) and Perlin s (188) recent report of the quantitative thermal decomposition of algin at 255 C. 

Sulfur oxides and nitrogen oxides may be removed from combustion gases by various processes. One of the cost-effective and efficient methods involve dry scrubbing of SOx and NOx over lanthanide-oxygen-sulfur compounds (Jalan and Desai 1992). Cerium sulfate is found to be an effective catalyst toward the reduction of NOx by ammonia. A combined removal of NOx and SOx has been achieved using cerium oxide doped with strontium oxide, lanthanum oxide, calcium oxide, or cerium sulfate. 

Alkyl hydroperoxides may be used in place of HjOj. A similar reaction is observed when cerium(lV) sulfate oxidizes an alcohol ... 

The oxides, (R.E.)203, are readily soluble in acids unless they have been ignited at high temperatures, in which case they dissolve more slowly. However, cerium(IAr) oxide dissolves in acids exceedingly slowly. It may be converted to the anhydrous sulfate by heating with concentrated sulfuric acid or may be reduced to cerium (III), and thus rendered soluble, by means of hydrogen peroxide or alkali metal iodide in acidic solution. 

Although the rare earths are conveniently stored as oxalates or double sulfates, they are frequently converted to oxides for storage and, particularly, for use in reactions. However, if the sample of rare earth material contains an unusually large amoimt of cerium, it is not advisable to convert it to oxides because of the difficulty of dissolving cerium(IV) oxide in common reagents. 

Cerex U 60. See Olive oil PEG-6 esters Cerfak N-100. See Cocamide DEA Ceria. See Cerium oxide Ceric acid. See Cerotic acid Ceric oxide. See Cerium oxide Ceric sulfate tetrahydrate. See Cerium sulfate (ic)... 

Cerium(IV) ion is a potent one-electron oxidant. cerium(IV) ammonium nitrate (CAN), is the most widely utilized cerium(rV) oxidizing agent, but cerium(IV) ammonium sulfate (CAS) is a good substitute when complications due to the involvement of nitrate ligands occur, resulting in side products such as nitrate esters. ... 

A study of the cerium(IV) oxidation of hydroquinone and hydroquin-one esters has been undertaken to investigate coupling of phosphorylation to two-electron oxidation. Reactions of substituted hydroquinones are thought to be inner sphere since there is little rate variation with structure (Table 3.2), and Marcus predictions lead to lower estimates of the rate. Although slower than other hydroquinones, the phosphate and sulfate esters show little difference in reactivity, implying that little P-O or S-0 stretching is required to obtain the semiquinone radical. 

Cerium(IV) oxide Ce02 -1-26 Erbium sulfate octahydrate Er2(S04)3-8H20 -r74600... 

The chemistry of some cerium(iv), thorium(iv) and lanthanum(iii) compounds in chlorosulfonic acid has been examined. Cerium(iv) oxide, sulfate, perchlorate, acetate, nitrate and chloride are all solvolysed to the Ce(S03Cl)4 species, which behaves as a nonelectrolyte. Thorium(iv) oxide, nitrate, acetate and chloride are solvolysed to H2[Th(S03Cl)6], a weak acid. Lanthanum(iii) oxide, sulfate, acetate and chloride form H[La(S03Cl)4], a very weak acid. ... 

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