Synthesis of ultrafine zeolites by dry-gel conversion without any organic additive

ZSM-5, mordenite, cancrinite and Y zeolites were successfully crystallized by the dry-gel conversion (DGC) without any organic additive (or template), in which the crystal particles of ZSM-5, mordenite and Y zeolite were well controlled in the range of ultrafine size. With a molar ratio of SiO2/Al2O3 ≤40, the pure ZSM-5 zeolite was obtained at 170 °C at the Na2O/SiO2 molar ratio <0.2, but the pure mordenite was formed at 150 °C at the Na2O/SiO2 molar ratio >0.25. When the dry-gel with a composition of 5.0Na2O:Al2O3:5.0SiO2 was crystallized at 140 °C for 24 h, pure cancrinite phase was obtained. TEM images showed that thus-crystallized zeolites consisted of ultrafine particles ranging 35–150 nm for ZSM-5, 50–200 nm for mordenite and 120–200 nm for zeolite Y, respectively. Different from ZSM-5, mordenite and cancrinite zeolites, the DGC synthesis of Y zeolite required more water in the dry-gel before crystallization.