Synthesis of MCM-22 zeolite by an ultrasonic-assisted aging procedure

The synthesis of MCM-22 zeolite under hydrothermal crystallization conditions has been performed by an ultrasonic-assisted aging procedure. The ultrasonic-assisted aging of the initial aluminosilicate gel can shorten the crystallization time of MCM-22, decrease the amount of hexamethyleneimine (HMI) used, and broaden the range of SiO2/Al2O3 ratios. By using the ultrasonic aging, pure phase of high-silica MCM-22 products with SiO2/Al2O3 > 100 can be obtained. When SiO2/Al2O3 ⩽ 50, high crystalline MCM-22 zeolites with the reduced average crystal sizes can be made even with low HMI/SiO2 ratio of 0.05 under static crystallization conditions. The acoustic cavitation of the ultrasonic is believed to be responsible for these positive results due to its cracking the crystal seeds and improving the solubility of silicate species.