Oxides manganese-based

Many SCR catalysts containing transition metals, such as Fe, Mn, Cr, Cu, have shown good activities for low-temperature SCR [2, 3, 6, 55-68]. Among these catalysts, manganese-based oxides have been extensively studied due to their excellent low-temperature SCR performance. Here, the pure manganese oxides, manganese-based mixed oxides (composite oxides), and supported manganese oxide catalysts are reviewed. 

Other metal oxide catalysts studied for the SCR-NH3 reaction include iron, copper, chromium and manganese oxides supported on various oxides, introduced into zeolite cavities or added to pillared-type clays. Copper catalysts and copper-nickel catalysts, in particular, show some advantages when NO—N02 mixtures are present in the feed and S02 is absent [31b], such as in the case of nitric acid plant tail emissions. The mechanism of NO reduction over copper- and manganese-based catalysts is different from that over vanadia—titania based catalysts. Scheme 1.1 reports the proposed mechanism of SCR-NH3 over Cu-alumina catalysts [31b],... 

Pointing out that the acidic nature of LiPFe assists the dissolution of Mn + into electrolyte solution, the authors speculated that HF in the electrolyte solution efficiently cleans up the spinel surface of MnO therefore, the bulk electrolyte solvents can be continuously exposed to the fresh surface of Mn204 and be oxidized. As a result, solvent oxidation would proceed more rapidly as compared with the case of an electrolyte that is less acidic. Therefore, for a spinel manganese-based lithium ion cell, a higher thermal safety would be obtained with lower salt concentration, and the authors suggested 0.5 M as the optimum concentration at which the ion... 

The earliest methods for preparing cyclic a-diazo ketones involved the oxidation of the monohydrazones prepared from a-diketones, generally using mercuric oxide.7,8 Recent modifications of this procedure include the use of calcium hypochlorite in aqueous sodium hydroxide or activated manganese dioxide as oxidants.1 The latter reagent, especially, hoc ms preferable to mercuric oxide. The base-catalyzed decomposition of tile monotosylhydrazoneH of a-diketones has been... 

It is based on the addition of Mn2+ solution, followed by die addition of a strong alkali to die sample in a glass-stoppered bottle. Dissolved 02 rapidly oxidizes an equivalent amount of the dispersed divalent manganous hydroxide precipitate to hydroxides of higher valence states. In die presence of iodide ions in an acidic solution, the oxidized manganese reverts to die divalent state, with die liberation of a quantity of iodine equivalent to die original dissolved 02 content. The iodine is then titrated with a standard solution of thiosulfate. The titration end point can be detected visually with a starch indicator, or by potentiometric techniques. The liberated iodine can be determined colorimetrically. 

Dinitrocresols present in water samples, especially when present at low concentrations, can be lost via oxidation by hypochlorite (Di Corcia and Marchetti 1992). This can be eliminated through the addition of sodium sulfite prior to extraction. In the multiresidue method of Chen et al. (1991), Mn + dissolved in the sample would be oxidized to manganese(lll,IV) oxides during base extraction, which in turn would oxidize the phenols during acid extraction. The oxidation of phenols can be eliminated by adding sodium thiosulfate to the sample prior to extraction or extraction at acidic pH as the first step, providing that manganese(lll,IV) oxides are not present in the sample before extraction. 

Other kinds of mesoporous manganese based materials have been also reported by transformation of layered bimessite (18). Finally amorphous microporous manganese oxidic materials prepared by the reaction between KMn04 and oxalic acid and incorporation of hetero-cations like Cu, Cr and Zn in them have been recently prepared and tested as catalysts (19, 20). 

All of the examples described above involve stoichiometric imido transfer to the alkene substrate. A crucial advance in the area of catalytic oxidation was made by Mansuy, who disclosed the first example of catalytic aziridination of alkenes in 1984 [10]. Both iron- and manganese-based porphyrin complexes were found... 

We thus see that although iron when present alone is a catalyst for the oxidation reaction, it has almost no effect on the rate of reaction when manganese is present. Since several catalysts are normally present in scrubbing system liquors, care must be taken in predicting oxidation rates based on information on individual catalysts. 

Fig. (20). Photoanode consisting of titania sensitized Ru dye coated over a nafion layer doped with manganese based water oxidation catalyst along with the cross sectional arrangement of photoelectrochemical cell. Reproduced with permission from Ref. [179] 2010 American Chemical Society.

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