Hydrothermal conversion of FAU zeolite into LEV zeolite in the presence of non-calcined seed crystals

Hydrothermal conversion of Faujasite-type (FAU) zeolite into Levynite (LEV) zeolite without the use of an organic structure-directing agent (OSDA) was successfully achieved in the presence of non-calcined seed crystals. The interzeolite conversion depended strongly upon the alkalinity (OH −/SiO 2) of the starting gel, the Si/Al ratio of the starting FAU zeolite and the type of alkaline metal employed. Successful conversion of FAU zeolites into pure LEV zeolite was achieved only for FAU zeolites with Si/Al ratios in the range of 19–26, under highly alkaline conditions (OH −/SiO 2=0.6) by using NaOH as an alkali source. Although the yield of LEV zeolite prepared by this method was lower (18–26%) than that of the conventional hydrothermal synthesis with the use of SDA, the obtained LEV zeolite exhibited a unique core/shell structure. ► Pure LEV zeolite was obtained from FAU zeolite in the presence of non-calcined seed crystals. ► The FAU–LEV interzeolite conversion occurred without the use of an additional OSDA. ► The obtained LEV zeolite exhibited a unique core/shell structure.