Theorists in the UK have studied the aluminium distribution in a number of catalytically active zeolite species, finding evidence that –Al–O–Al– linkages could exist in some zeolite species after all.1
Source: Royal Society of Chemistry
Löwenstein’s rule of ‘aluminium avoidance’ says that that –Al–O–Al– bonds are forbidden but new research hints that this motif may not be as elusive as is generally believed
Since Löwenstein first published his study on ‘the distribution of aluminium in the tetrahedra of silicates and aluminates’ in 1954,2 scientists had generally accepted that aluminium clusters cannot exist within zeolite structures. Löwenstein’s rule of ‘aluminium avoidance’ states that whenever two tetrahedra are linked by an oxygen bridge, if the centre of one is occupied by an aluminium atom, the other must be occupied by silicon. As such, Löwenstein’s rule prohibits –Al–O–Al– linkages from occurring within zeolites, and dictates that the ratio of Al:Si in zeolites must be 1:1.
Read the full story by Hannah Dunckley on Chemistry World.
1 R E Fletcher, S Ling and B Slater, Chem. Sci., 2017, DOI: 10.1039/c7sc02531a (This article is open access.)
2 W Löwenstein, Am. Mineral., 1954, 39, 92