Morphology-controlled synthesis of large mordenite crystals

The morphology-controlled synthesis of mordenite (MOR) zeolites was achieved using the acidic hydrolysis route, which was started by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS), followed by switching the synthetic gel to basic conditions for hydrothermal crystallization. The synthesis by using tetraethylammonium hydroxide as the template resulted in a series of large MOR crystals with different morphologies, such as bulky sphere, circular pie, flat prism, hexagonal star-like prism and ellipsoid. Moreover, column, elongated spindle, short spindle, petal and circular pie shaped MOR crystals could be obtained without using an organic template in the above synthetic route. Among these morphologies, the bulky sphere, hexagonal star-like prism and petal shaped crystals were generated on MOR zeolites for the first time. The obtained products were characterized by XRD, SEM and N₂ adsorption experiments. Various synthetic parameters were systematically investigated, including hydrolysis conditions for TEOS, molar composition of the initial gel, crystallization time and temperature. The results demonstrated that MOR zeolites can be synthesized through the acidic hydrolysis route, and their morphology can be facilely controlled through tuning the elemental synthetic conditions.