Amorphous Aluminium Compounds

Because of its ability to probe the atomic environment in compounds which do not possess long-range order, MAS NMR has become a technique of choice for studying the constitution of amorphous materials, including gels and glasses which contain relatively sensitive NMR-active nuclei, and their thermal transformation into crystalline compounds. 

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The EDX spectrum (Fig. 11.8) shows the main surface scale impurity peaks of silica, aluminium, sodium, chloride and iron. If this EDX is compared to that of a new, clean membrane surface (Fig. 11.9), the clean surface shows sulphur, carbon and oxygen, which is typical of a porous polysulphone support. It was concluded that the scale is amorphous, composed of aluminosilicate and silicate. These compounds are normally found in trace amounts in brine solutions. Analysis showed that the surface could be cleaned with hydrochloric acid and analysis of the dissolved scale was similar to the EDX spectrum analysis. Review of the plant operation determined that the precipitation was the result of high pH in combination with high silica concentrations in the brine. 

Compound 85 was dehydrogenated at 300° over palladium black under reduced pressure to a pyridine derivative 96 which was independently synthesized by the following route. Anisaldehyde (86) was treated with iodine monochloride in acetic acid to give the 3-iodo derivative 87. The Ullmann reaction of 87 in the presence of copper bronze afforded biphenyldialdehyde (88). The Knoevenagel condensation with malonic acid yielded the unsaturated diacid 91. The methyl ester (92) was also prepared alternatively by a condensation of 3-iodoanisaldehyde with malonic acid to give the iodo-cinnamic acid (89), followed by the Ullmann reaction of its methyl ester (90). The cinnamic diester was catalytically hydrogenated and reduced with lithium aluminium hydride to the diol 94. Reaction with phosphoryl chloride afforded an amorphous dichloro derivative (95) which was condensed with 2,6-lutidine in liquid ammonia in the presence of potassium amide to yield pyridine the derivative 96 in 27% yield (53). 

A detailed investigation of soft mechanochemical synthesis of aluminium titanate was described in [60]. The data obtained in this study are the evidence of the formation of amorphous hydrated aluminium titanium compounds at the initial stages. These compounds are stable till 450-700°C at higher temperature they decompose to give aluminium and titanium oxides which form dispersed aluminium titanate at 1340°C. 

The stabilisation of the zeolites using heat treatment under steam (vapour treatment) causes migration of aluminium out of the lattice. The result is the formation of an amorphous compound that can be detected by XRD in the form of a poorly defined scattering back-... 

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