Aluminium oxide-hydroxides

Linton DJ, Wheatley AEH (2003) The Synthesis and Structural Properties of Aluminium Oxide, Hydroxide and Organooxide Compounds 105 67-139 Lo KK-W (2007) Luminescent Transition Metal Complexes as Biological Labels and Probes. 123 205-245... 

The Synthesis and Structural Properties of Aluminium Oxide, Hydroxide and Organooxide Compounds... 

Lastly, the positions of hydrogen atoms have been located in a series of low-surface-area aluminium oxide-hydroxides. Hence, the long known solid-state structures of diaspore (a-AlOOH) and boehmite (y-AlOOH) have been recently probed using H CRAMPS [45] along with X-ray and neutron diffraction techniques [46]. For diaspore results point to the presence of Alaf/Xa-OH) groups with 6-fold and 4-fold coordination at aluminium and oxygen, respectively, while Al2(/x-OH) moieties with 6-coordinate aluminium and 3-coordinate oxygen are revealed in boehmite [46]. 

Lastly, the previously-mentioned study into the low-surface-area aluminium oxide-hydroxides diaspore and boehmite by CRAMPS (Section 2.2.1) [46] has also been extended to the aluminium hydroxides gibbsite and bayerite, revealing three distinct resonances in a 3 2 1 ratio in these systems and suggesting the presence of Al2(/r-OH) groups with 6-coordinate metal centres. 

AIHO2 (s) AlOOH (s) Aluminium Oxide Hydroxide Boehmite AIHO2 (s) AlOOH (s)... 

Of the aluminium compounds with low solubility, hydrated aluminium oxide (usually called aluminium hydroxide with a non-stoichiometric structure) is of particular interest in hydrochemistry and the technology of water, and it is present mainly in the colloidal form. The structure A1(0H)3 corresponds only to the compound formed by precipitation of aluminium solutions by introducing carbon dioxide. At a higher temperature during precipitation with ammonia, aluminium oxide-hydroxide AIO(OH) can also be formed. When removing phosphates from water aluminium phosphate plays an important role it is stable in weakly acid media but is hydrolysed to A1(0H)3 in alkaline media. 

The electrolytic production of aluminium is more complex. Hall and Heroult developed the current process independently in 1886. In this process, alumina, AI2O3, is dissolved in molten sodium aluminium fluoride (Na3AlF6) and electrolysed (Figure 9.22). Originally, the aluminium oxide was derived directly from the mineral bauxite, and the sodium aluminium fluoride was used in the form of the naturally occurring mineral cryolite. These days, synthetic cryolite is used, and the aluminium oxide is produced from a wider variety of mineral sources, consisting of aluminium oxide-hydroxides. 

Ruthenium-aluminium oxide/hydroxide catalyst ( 2.5wt% Ru loading). The preparation of this catalyst is described in Chapter 8 because it consists of Ru(0) nanoparticles encapsulated in an aluminium oxy-hydroxide... 

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