Static Synthesis and Crystallization Mechanism of ZSM-35 Zeolite

The pure ZSM-35 zeolite was synthesized in a static hydrothermal system at 220 degrees C using cyclohexylamine as the template and silica sol as the Si source. When the initial gel contained a certain amount of K(+), the mutual role of K(+) and Na(+) inhibited the formation of mordenite, and well crystallized product was formed with n(K(+))/n(K(+)+Na(+)) = 0.3. Optimum regions of the synthetic conditions of ZSM-35 zeolite obtained by X-ray diffraction were n(M(2)O)/n(Al(2)O(3)) = 3.2-3.4 and n(SiO(2))/n(Al(2)O(3)) = 22. The building units in the precursor were identified as five-membered and six-membered silicate rings by UV-Raman spectroscopy. The intensity of the Raman band at 450 cm(-1) increased in the beginning of crystallization, and the new bands at 421, 312, and 215 cm(-1) appeared with consuming the amorphous gel, indicating that the ring species were turned out to be aggregate through the hydrothermal treatment, and finally formed ZSM-35 zeolite. The strong Raman band at 421 cm(-1) should be assigned to the bending vibration of the five-membered silicate ring, and the Raman band at 312 cm(-1) might correspond to the six-membered silicate ring of ZSM-35 zeolite framework.