Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis

Siting of Al atoms in the framework T sites, in zeolite rings and channel/cavity system, and the distribution of Al atoms between single Al atoms and close Al atoms in various Al-O-(Si-O)n-Al sequences in Si-rich zeolites represent key parameters controlling properties of counter ion species. Framework Al siting and distribution is not random or controlled by simple rules and depends on the conditions of the zeolite synthesis. Al in Al-O-(Si-O)2-Al in one 6-MR and single Al atoms predominate in Si-rich zeolites and their population can be varied to a large extent. The siting and distribution of framework Al atoms dramatically affect catalytic activity/selectivity both of protonic and transition metal ion-containing zeolite catalysts.