Potassium aluminate, structure

Initially, there are several types of micas which have similar properties but which have different physical and chemical origins. Illite, the low potassium aluminous mica-like mineral ( 10 X, non-expandable structure upon glycollation) can form diagenetically (Velde and Hower,... 

Since cristobalite has the same structure as potassium aluminate, as shown in Fig. 19 (with the difference that no potassium ions are in the... 

Mica is a generic name to describe a group of complex hydrous potassium aluminate silicate materials, differing in chemical composition, but sharing a unique laminar crystalline structure. In nature, mica develops in a book-like form. The individual platelets can be delaminated into very thin high aspect ratio particles that are tough and flexible. Of the commercially important forms, muscovite and phlogopite are used as reinforcements for plastics. 

Craig, F.J., Kennedy, A.R., Mulvey, R.E. and Spicer, M.D., Structures of the potassium aluminates [ K2(Me3A10Bu )2 pmdetajoo] and [ K(pmdeta)2 (AlMe4) ] How the nature of the alane reagent determines which of these products form from alkoxide-containing reaction mixtures, Chem. Commun. (16), 1951-1952 (1996). 

The presence of potassium on iron during ammonia pretreatment has no additional effect on the restructuring process when adsorbed alone or when coadsorbed with Al O. Thus, potassium does not seem to affect the structural promotion of ammonia synthesis catalyst either during ammonia or water-vapor pretreatment. However, the presence of potassium on a Al O /Fe surface, during water-vapor pretreatment (Section 4.6), inhibits restructuring. A likely explanation for this observation is that the formation of potassium aluminate blocks the interaction between iron oxide and aluminum oxide. ... 

Figure 17. Proposed phase relations where K is a mobile component and Al, Fe are immobile components at about 20°C and several atmosphere water pressure for aluminous and ferric-ferrous mica-smectite minerals. Symbols are as follows I illite G = non-expanding glauconite Ox = iron oxide Kaol = kaolinlte Mo montmorillonite smectite N nontronitic smectite MLAL aluminous illite-smectite interlayered minerals Mlpe = iron-rich glauconite mica-smectite interlayered mineral. Dashed lines 1, 2, and 3 indicate the path three different starting materials might take during the process of glauconitization. The process involves increase of potassium content and the attainment of an iron-rich octahedral layer in a mica structure.

SCHULTZ (L.G.), 1969. Lithium and potassium absorption, dehydroxylation temperature, and structural water content of aluminous smectites. Clays and Clay Min. 1 7, 115-49. 

Of these, the P- and P"-aluminas have been studied most extensively. The isostructural sodium gallates, potassium, rubidium and cesium gallates, aluminates, and ferrites are also known. The ideal formulas for the p and P" structures are AMuOn and A2M11O17, respectively, but all of the compounds are intrinsically nonstoichiometric and the actual alkali content is always greater than unity but less than 2. The most obvious charge compensation mechanism is alower-valence cation substitution for trivalent M , namely Ai, )Oi7 (M = Mg, Co, Ni, Zn) and... 

Hydrated montmorillonite has water between the silicate-aluminate-silicate layers. The micas (e.g., muscovite) have potassium ions in comparable positions and also have aluminum substituting for silicon in about 25% of the silicate sites. Changes in the proportions of aluminum and silicon in either of these allow the introduction of other cations and the formation of a large number of minerals. The layered structures of some micas are pronounced, allowing them to be cleaved into sheets used for high-temperature applications in which a transparent window is needed. They also have valuable insulating properties and are used in electrical devices. 

Methane or natural gas steam reforming performed on an industrial scale over nickel catalysts is described above. Nickel catalysts are also used in large scale productions for the partial oxidation and autothermal reforming of natural gas [216]. They contain between 7 and 80 wt.% nickel on various carriers such as a-alumina, magnesia, zirconia and spinels. Calcium aluminate, 10-13 wt.%, frequently serves as a binder and a combination of up to 7 wt.% potassium and up to 16 wt.% silica is added to suppress coke formation, which is a major issue for nickel catalysts under conditions of partial oxidation [216]. Novel formulations contain 10 wt.% nickel and 5 wt.% sulfur on an alumina carrier [217]. The reaction is usually performed at temperatures exceeding 700 °C. Perovskite catalysts based upon nickel and lanthanide allow high nickel dispersion, which reduces coke formation. In addition, the perovskite structure is temperature resistant. 

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