Manganese-chromium oxide

Acetic add Zinc manganese chromium oxides 400 200 Ethyl, propyl, and butyl alcohols 1... 

These observations, when extended to other oxides or mixtures of oxides, gave in part confirmatory data and, in one case, that of manganese-chromium oxide, data which significantly differed from those obtained with zinc oxide. Thus, with chromium oxide gel with a surface area of 189.5 sq. meters/g. the quantities of gas involved in the desorption-readsorption phenomena between 56 and 302° C. amounted to 9 cc. or nearly 5% of the total surface. With a zinc chromium oxide of 21 sq. meters/g. the area involved in desorption-readsorption phenomena was 13% of the total surface between 0 and 302° C. With manganese-chromium oxide, on the other hand, no readsorption of gas was observed when the sample was cooled in hydrogen from 218 to 0° C. 

A detailed study of the dehydrogenation of 10.1 l-dihydro-5//-benz[6,/]azcpinc (47) over metal oxides at 550 C revealed that cobalt(II) oxide, iron(III) oxide and manganese(III) oxide are effective catalysts (yields 30-40%), but formation of 5//-dibenz[7),/]azepinc (48) is accompanied by ring contraction of the dihydro compound to 9-methylacridine and acridine in 3-20 % yield.111 In contrast, tin(IV) oxide, zinc(II) oxide. chromium(III) oxide, cerium(IV) oxide and magnesium oxide arc less-effective catalysts (7-14% yield) but provide pure 5H-dibenz[b,/]azepine. On the basis of these results, optimum conditions (83 88% selectivity 94-98 % yield) for the formation of the dibenzazepine are proposed which employ a K2CO,/ Mn203/Sn02/Mg0 catalyst (1 7 3 10) at 550 C. 

The advantage is an oxidation temperature of 500°F compared to non-catalytic combustion of 1500°F. The active ingredients used were platinum, as well as the base metal oxides of cobalt, nickel, manganese, chromium, and iron. The support material included nickel-chromium ribbons, ceramics rods, beads, and pellets (13-17). 

Examples of metals which are prepared by the metallothermic reduction of oxides include manganese, chromium, vanadium, zirconium, and niobium. In a manner similar to the production of magnesium by the Pidgeon process, some of the rare earth metals have been produced by the metallothermic reduction-distillation process. 

Arul Dhas N, Koltypin Y, Gedanken A (1997) Sonochemical preparation and characterization of ultrafine chromium oxide and manganese oxide powders. Chem Mater 9(12) 3159—3163... 

Hitachi Cable Ltd. (35) has claimed that dehydrogenation catalysts, exemplified by chromium oxide—zinc oxide, iron oxide, zinc oxide, and aluminum oxide—manganese oxide inhibit drip and reduce flammability of a polyolefin mainly flame retarded with ATH or magnesium hydroxide. Proprietary grades of ATH and Mg(OH)2 are on the market which contain small amounts of other metal oxides to increase char, possibly by this mechanism. 

The production of metals which form very stable oxides by the aluminothermic process, such as manganese, chromium and vanadium is carried out with reactants at room temperature which react to provide enough heat to raise the temperature of the products to high temperatures at which the whole system is liquid. The metal phase which is produced can therefore separate from the liquid slag which is formed. The production of chromium serves as a useful... 

The microstructure of commercial varistors is extremely complex, and commercial preparations also contain other dopants, mainly oxides of cobalt, manganese, chromium, and antimony, that are used to fine tune the varistor characteristics. The transition-metal dopants are chemically similar to Zn2+ and mainly form substitutional defects within the ZnO grains, such as CoZn, that modify the n-type behavior of the grain interior. (See also Chapter 8 for further discussion of the electronic... 

Strangely enough, a combination similar to the ammonia catalyst, iron oxide plus alumina, yielded particularly good results (32). Together with Ch. Beck, the author found that other combinations such as iron oxide with chromium oxide, zinc oxide with chromium oxide, lead oxide with uranium oxide, copper oxide with zirconium oxide, manganese oxide with chromium oxide, and similar multicomponent systems were quite effective catalysts for the same reaction (33). 

The oxidation of alcohols to the corresponding aldehydes, ketones or acids certainly represents one of the more important functional group transformations in organic synthesis and there are numerous methods reported in the literature (1-3). However, relatively few methods describe the selective oxidation of primary or secondary alcohols to the corresponding aldehydes and ketones and most of them traditionally use a stoichiometric terminal oxidant such as chromium oxide (4), dichromate (5), manganese oxide (6), and osmium or ruthenium oxides as primary oxidants (7). 

Oxides.—Amongst the simple oxides may be classed —oxide of chromium, oxide of iron, oxide of uranium, oxide of manganese, oxide of zinc, oxide of cobalt, oxide of antimony, oxide of copper, oxide of tin. 

Common chemical properties The alkali metals are so chemically reactive that they are never found free in nature. Sodium and potassium react explosively with water to produce hydrogen gas. The alkaline earth metals are not quite as reactive as the alkali metals. The alkali metals react with water but not explosively. The transition metals are generally the least reactive of all the metals. However, when they combine with other elements, they form a large variety of colored compounds. Chromium oxide is green, titanium oxide and zinc oxide are white, manganese oxide is purple, and iron oxide is ochre. 

The solution at 85° has a lustrous bronzy appearance as the dye precipitates from the concentrated zinc chloride solution. After 30 minutes, the mixture is allowed to cool to 50°C., and 70 grams of concentrated sulfuric acid is added to dissolve the manganese salts, aluminum hydroxide, and chromium oxide. The dye is filtered off at 20° and washed with a small volume of 10 per cent salt solution. This crude product is dissolved in 1 liter water at 100°, the solution is filtered, and the dye is reprecipitated by the addition of 50 grams of ordinary 50 per cent zinc chloride solution and 150 grams of salt. The zinc chloride double salt of the dye separates completely in 24 hours in the form of beautiful bronzy red crystals which are filtered off, washed with 10 per cent salt solution, and dried at 50° (no higher). The yield of pure, concentrated dye is about 44 grams. 

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