Influence of the ultrasonic-assisted synthesis on Al distribution in a MOR zeolite: from gel to resulting material

Two Al-rich mordenite samples were prepared by the same synthesis procedure except for the activation of the gel for which classical stirring and ultrasonic pretreatment was used. The organization of Al atoms both in the synthesis gel and zeolite product was investigated. Although both methods of the gel activation resulted in a similar transformation of Al and Si source according to NMR spectroscopy, stirring provided a significantly higher fraction of AlSiAl sequences in the gel compared to the ultrasonic pretreatment. These sequences were transferred to the zeolite product and were more populated in the conventionally prepared mordenite. Al atoms of AlSiAl sequences face different channels and mainly behave as single Al atoms, but they can also form Al pairs or close unpaired Al atoms, observed for the first time for mordenite.