Amorphous aluminum, effect

Heating a phenol ester in the presence of Nafion-H gave good yields of the hydroxy phenyl ketone.This Fries rearrangement gave a mixture of the ortho and para hydroxy compounds in a 1 2-2.5 ratio (Eqn. 22.19). A study of the rearrangement of phenyl benzoate over a number of solid acid catalysts indicated that Nafion-H was more effective than montmorilIonite or amorphous aluminum silicate for this reaction. " ... 

The possible role of amorphous aluminum and silicon oxides as controls. These merit further investigation since Elgabaly (66) foimd increased zinc fixation by kaolinite after nine days of grinding even though Tiller et al. (239) found little effect of sodium hydroxide extractions on cobalt sorption by soil clays. Tiller (237) has recently found that zinc sorption by montmorillonite is enhanced by the addition of soluble silicon. 

US stat ent can be validated both through model experiments and with rigoroi mathematical analyses of the properties of adsorption isotherm equations. However, the point that these equations are not unique mathematical descriptions of surface reactions in soils can be made effectively by a simple counterexample. Consider a typical batch sorption experiment in which o-phosphate is reacted with soil material and suppose that in this reaction an amorphous aluminum phosphate phase is formed. 

An opposing effect is possible under the severe conditions of a single extraction with HC1 some of the aluminum removed from the crystal structure may not be transported out of the catalyst particle. The resulting amorphous alumina, (after subsequent calcining) remaining in the particle would cause some reduction in effective diffusivity. Such amorphous alumina has been suggested by others (17,18). 

The aluminum in the zinc phosphate cements was considered very important, van Dalen [21] recognized its importance first. The reaction of zinc oxide and phosphoric acid was greatly moderated by aluminum. This effect was attributed to formation of an aluminum phosphate gelatinous coating on zinc oxide particles. In fact, Wilson and Nicholson believe that the gelatinous substance may even be zinc aluminophosphate phase [3], which subsequently crystallizes into hopeite and aluminophosphate amorphous gel (AlP04-nH20). 

Coprecipitation with the hydrous oxides, such as of iron(III) and aluminum, occurs by adsorption and possibly also by compound formation. The precipitates, coming down in either amorphous or finely crystalline form with extensive surface, adsorb large amounts of water and adsorb hydroxide ions as potential-determining ions. Figure 9-1 illustrates the effect of varying the concentration of ammonium chloride and ammonium hydroxide on the amount of coprecipitation of divalent metal ions with hydrous iron(III) oxide. When the concentration of ammonium chloride is increased at a constant ammonia concentration, the adsorption is decreased... 

The collapse to an amorphous phase is the most pronounced effect accompanying treatments of zeolites at elevated temperatures. In addition, heating results in changes in the framework composition, caused by movement of the tetrahedral aluminum into extra-lattice positions. 

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