Calcium magnesium aluminates

In the vapor phase, acetone vapor is passed over a catalyst bed of magnesium aluminate (206), 2iac oxide—bismuth oxide (207), calcium oxide (208), lithium or 2iac-doped mixed magnesia—alumina (209), calcium on alumina (210), or basic mixed-metal oxide catalysts (211—214). Temperatures ranging... 

The coagulant sodium aluminate (NaA102) is strongly caustic (contributing hydroxide alkalinity to the BW) and reacts with calcium and magnesium salts and any silica present to form a zeolite sludge of calcium-magnesium-aluminum silcate. 

Several different possible zeolite structures may result, and if the sodium content is too high, calcium and magnesium are excluded and a hard zeolite scale of sodium-aluminum silicate preferentially forms. If only calcium is present, calcium-aluminum silicate zeolite forms, also as a hard scale. If only magnesium is present in solution, it forms the flocculant magnesium aluminate, MgAl204. 

Catalysts. - Group VIII metals, conventional base metal catalysts (Ni, Co, and Fe) as well as noble metal catalysts (Pt, Ru, Rh, Pd) are active for the SR reaction. These are usually dispersed on various oxide supports. y-Alumina is widely used but a-alumina, magnesium aluminate, calcium aluminate, ceria, magnesia, pervoskites, and zirconia are also used as support materials. The following sections discuss the base metal and noble metal catalysts in detail, focusing on liquid hydrocarbon SR for fuel cell applications. 

The various support materials have different effects on potential carbon formation. This seems to go in parallel with the Lewis/Bronsted acidity. The main commercially used catalyst supports can be ranked as follows in decreasing order of carbon forming tendency (and thus in decreasing order of the important minimum practical steam/ carbon ratio) a-alumina > magnesium aluminate (spinel) > calcium aluminate > alkalized calcium aluminate [419],... 

Use of a support made of an alkaline earth metal compound [3 If]. Tribasic calcium phosphate, calcium carbonate, calcium fluoride, strontium titanate and magnesium aluminate are optimal supports. 

Other effective antacids, which are used separately or with aluminum hydroxide or magnesium trisilicate, include dihydroxyaluminum amino-acetate, hydrated magnesium aluminate, dihydroxyaluminum sodium carbonate, and others. Each of these compounds has been demonstrated to be as useful as antacids but has not been so popular as calcium carbonate or aluminum hydroxide. 

Koe] Koehler, M.F., Barany, R., Kelley, K.K., Heats and Free Energies of Formation of Ferrites and Aluminates of Calcium, Magnesium, Sodium, and Lithium , Report of Investigations, US. Bureau of Mines, 5711, 1-14 (1961) (Experimental, Thermodyn.,, 32)... 

This suggests that the surface of flame retardants can be altered in ways that can improve their performance, particularly ignition performance. Other additive systems may benefit, such as crystalline ionic materials containing multiple cations such as calcium aluminate, zinc borate and calcium/magnesium carbonates. Further research is underway and this should yield useful information about the electron donor capabilities of certain materials and the role this plays in flame retardancy. 

To improve magnesium reduction, which also improves siHca reduction in cold process softening, sodium aluminate may be used. The sodium aluminate provides hydroxyl ion (OH ) needed for improved magnesium reduction, without increasing calcium hardness in the treated water. In addition, the hydrolysis of sodium aluminate results in the formation of aluminum hydroxide, which aids in floe formation, sludge blanket conditioning, and siHca reduction. 

In this method, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, or sodium aluminate can be fed to the spent fixer for precipitation of silver ions as insoluble silver hydroxide precipitates. Figure 7 indicates that the residual silver concentration in the hydroxide precipitation treated effluent can be about 1 mg/L at pH 12 [19]. 

Reacts with calcium and magnesium hydrides in tetrahydrofuran forming tetrahydro aluminates, Ca(AlH4)2 reacts with hydrides of alkali metals in ether forming aluminum hydride ... 

This is by far the most frequently encountered interference in AAS. Basically, a chemical interference can be defined as anything that prevents or suppresses the formation of ground state atoms in the flame. A common example is the interference produced by aluminium, silicon and phosphorus in the determination of magnesium, calcium, strontium, barium and many other metals. This is due to the formation of aluminates, silicates and phosphates which, in many instances, are refractory in the analytical flame being used. 

Table 2.3 lists some phases containing MgO that are in varying degrees relevant to cement chemistry. It is not a complete list of phases with essential MgO in the CaO-MgO-AljOj-SiOj system. As seen in Chapter 1, some MgO is also taken up by all four of the major clinker phases, typical contents being 0.5-2.0% for alite, 0.5% for belite, 1.4% for the aluminate phase, and 3.0% for the ferrite phase. Magnesium oxide (periclase), like calcium oxide, has the sodium chloride structure it is cubic, with a = 0.4213 nm, space group Fm3m, Z = 4, = 3581 kgm (S5) and refrac-... 

Calcium oxide is the main ingredient in conventional portland cements. Since limestone is the most abundant mineral in nature, it has been easy to produce portland cement at a low cost. The high solubility of calcium oxide makes it difficult to produce phosphate-based cements. However, calcium oxide can be converted to compounds such as silicates, aluminates, or even hydrophosphates, which then can be used in an acid-base reaction with phosphate, forming CBPCs. The cost of phosphates and conversion to the correct mineral forms add to the manufacturing cost, and hence calcium phosphate cements are more expensive than conventional cements. For this reason, their use has been largely limited to dental and other biomedical applications. Calcium phosphate cements have found application as structural materials, but only when wollastonite is used as an admixture in magnesium phosphate cements. Because calcium phosphates are also bone minerals, they are indispensable in biomaterial applications and hence form a class of useful CBPCs that cannot be substituted by any other. 

For a naphtha feedstock,. the catalyst is based on nickel deposited on calcium or magnesium silico-aluminate incorporating potasskun, or nkkel on an alumina support with uranium promoter. Nickel on calcium aluminate is generally used for post-combustion. 

The primary reformer consists of a multitude of reformer tubes loaded with the nickel catalyst (15 25% NiO on aluminum oxide, calcium aluminate, or magnesium aluminum spinel support) in a furnace box, in which the heat needed for the reaction is transferred to the tubes by radiation. The heat is generated in burners, generally gas-fired in the furnace box. 

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