Iron-containing mixed oxides

Hofrnaim first formulated the concept of mixed oxidation states for Prussian blue and other iron-containing mixed valence species. The electronic origin of the color, of course, remained obscure until the development of quantum mechanics. Another concept, described as valence oscillation , was used by Hofinaim and Hoschele following the realization that organic dyes were often found to be unsaturated species with valence resonance an example is cerium-uranium blue (3). 

The aim of this work is to develop new Fe-Mo containing mixed oxides highly dispersed in a titania matrix, prepared by the sol-gel method, and to compare these materials to those of iron molybdate prepared by conventional methods (i.e. impregnation). Here, we report the preparation of sol-gel derived iron molybdenum titanium mixed oxides. The bulk composition and the textural properties of these materials are investigated by elemental chemical analysis and N2 adsorption, respectively. 

Modern WGS catalysts can be divided into four classes, namely, HTS, LTS, sour gas shift, and precious-metal-containing catalysts. Iron oxide or iron-chromium mixed oxides promote the WGS in the 350-450 °C range and are modified by MgO or ZnO for good sulfur resistance and mechanical strength. The second type of WGS catalysts are mixed copper-zinc oxides which promote WGS in... 

Mixed oxides of Fe(IV) can be prepared by heating iron(III) oxide with a metal oxide or hydroxide in oxygen at elevated temperatures. These black compounds have general formulas M FeO, M monovalent, or M2Fe04, M divalent, but do not contain discrete [FeOJ" ions. They are readily decomposed by mineral acids to iron(III) and oxygen. 

In 1789 M. H. Klaproth examined pitchblende, thought at the time to be a mixed oxide ore of zinc, iron and tungsten, and showed that it contained a new element which he named uranium after the recendy discovered planet, Uranus. Then in 1828 J. J. Berzelius obtained an oxide, from a Norwegian ore now known as thorite he named this thoria after the Scandinavian god of war and, by reduction of its tetrachloride with potassium, isolated the metal thorium. The same method was subsequendy used in 1841 by B. Peligot to effect the first preparation of metallic uranium. 

Mathew, T. Synthesis and characterization of mixed oxides containing cobalt, copper and iron and study of their catalytic activity , Ph. D Thesis, University of Pune, 2002. 

Since the discovery in 1951 that magnetoplumbite, BaFei20i9 is a hard, semiconducting ferrigmagnet of considerable technical interest, several other iron oxides with closely related hexagonal structures have been synthesized and studied. Of particular interest for this review are those containing mixed valency. 

The name ferrite was originally given to a class of mixed oxides having an inverse spinel structure and the formula AFe204 where A is a divalent metal ion. The term has been extended to include other oxides, not necessarily containing iron, which have similar... 

The copper sulfide and iron oxide from this reaction are then mixed with limestone, CaC03, and sand, Si02, in a blast furnace, where CuS is converted to Cu2S. The limestone and sand form molten slag, CaSi03, in which the iron oxide dissolves. The copper sulfide melts and sinks to the bottom of the furnace. The less-dense iron-containing slag floats above the molten copper sulfide and is drained off. The isolated copper sulfide is then roasted to copper metal ... 

Under ideal circumstances these oxides can react to form Fe,0 magnetite this compound is a mixed oxide containing iron(II) and iron(III) ions. The O 2 ions form a cubic close packed structure with the Fe 2+ ions in the octahedral sites and half of the Fe 3+ ions in tetrahedral and the other half in octahedral sites. 

Iron-containing oxides (either pure or mixed) (513) are known to catalyze many reactions, including selective oxidations, dehydrogenations, oxydehy-drogenations (514-516), and the water-gas shift (517). 

The speiss is crushed and ground with 20 pex cent, of sodium chloride till it passes a 30-mesh sieve, and then roasted in reverberatory furnaces. The chloridised product is extracted with water to remove unchanged salt and soluble compounds of cobalt, nickel, and copper. The copper is removed from the liquor by treatment with scrap-iron, and the cobalt and nickel are then precipitated with caustic soda, and the precipitate washed, dried, calcined, and ground. It contains about 40 per cent, of cobalt to 3 per cent, of nickel, since the latter is not attacked so readily as the former in chloridising the speiss the mixed oxides also contain about 15 ounces of silver per ton. 

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