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

Abstract 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 SiO 2 /Al 2 O 3 ≤40, the pure ZSM-5 zeolite was obtained at 170 °C at the Na 2 O/SiO 2 molar ratio 2 O/SiO 2 molar ratio >0.25. When the dry-gel with a composition of 5.0Na 2 O:Al 2 O 3 :5.0SiO 2 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.