Aluminum oxide stoichiometry ratio

Mixed y-Ga203-Al203 oxides of different stoichiometry were prepared by the solvothermal method from Ga(acac)3 and Al(OPr-i)3 as starting materials and were used as catalysts for selective reduction of NO with methane. The initial formation of gallium oxide nuclei controls the crystal structure of the mixed gallium-aluminum oxides. It is found that the acid density per surface area is independent of the Al Ga feed ratio but depends on the reaction medium (diethylenetriamine, 2-methylaminoethanol, toluene, 1,5-pentanediol etc.), whereby in diethylenetriamine the catalyst had lower densities of acid sites and showed a higher methane efficiency. 

Solving any reaction stoichiometry problem requires the use of a mole ratio to convert from moles or grams of one substance in a reaction to moles or grams of another substance. A mole ratio is a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction. This information is obtained directly from the balanced chemical equation. Consider, for example, the chemical equation for the electrolysis of melted aluminum oxide to produce aluminum and oxygen. 

Theoretical calculations [43] based on first principles molecular dynamics discussed in Sect. 3.2.6 have suggested that Mg Al LDHs are most stable for n = 3 (i.e. x = 0.25) and indeed many minerals, including hydrotalcite itself, have this stoichiometry [4]. It has been reported that the synthesis of LDHs (with benzoate or terephthalate anions in the interlayers) from solutions containing Mg/Al = 2, leads to LDHs having the same composition when the synthesis is carried out at moderate temperatures but LDHs with Mg/Al = 3 (plus AlOOH) when the reaction is carried out under hydrothermal conditions [44]. It was proposed that the latter ratio represents the thermodynamically most favorable product. A similar observation has been reported [45] for solutions with Ni VPe = 2, where hydrothermal preparation led to segregation of an LDH with Ni VPe = 3 and Ni Fe 204. An attempt to synthesize a Co sAl LDH resulted in partial oxidation of the Co and formation of a Co o.yCo o.s LDH with complete migration of Al " from the layers to generate interlayer aluminum oxy-species [46]. 

High-purity spinel is a chemically derived spinel powder made hy the co-precipitation of magnesium and aluminum complex sulfates, with subsequent calcination to form the oxide compound. Purities range from 99.98-99.995%. Since it is chemically derived, the stoichiometries can he adjusted for virtually any MgOiAljOj ratio. The ceramic powders prepared hy this process can he hot pressed into transparent window materials with exceptional IR transmission range. 

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