*3.4. E*ff*ect of SiO2 Content*

The effect of SiO2 content was also studied ranging from SiO2/Al2O3 = 1.5 to 10. The results showed that the phase purity was found to be more sensitive by varying the SiO2 content as compared to the K2O content and heating temperature (Table 1). Crystalline W-10 with a high silica content (Si/Al ratio = 1.22) and cubic morphology was obtained when the hydrogel with low silica content (SiO2/Al2O3 ratio = 1.5) was used. The solid was proven to be an EDI-type zeolite according to XRD and SEM analyses (Figures 7a and 8a). At a SiO2/Al2O3 molar ratio of 5.0, W-11 (Si/Al ratio = 2.53) with a pure MER crystalline phase was produced (Figures 7b and 8b). Further increasing the silica content led to the co-crystallization of MER- and LTL-type zeolites before single phase of LTL-type zeolite product was crystallized at a SiO2/Al2O3 molar ratio of 10 (Figure 7c,d and Figure 8c,d). As shown, the LTL-type zeolite (W-13), having a one-dimensional pore structure, possessed a higher framework silica content (Si/Al ratio = 3.05) and exhibited a novel spinning top-like shape instead of conventional cylindrical structure [33] owing to the silica source and the precursor molar composition used.

**Figure 7.** XRD patterns of (**a**) W-10, (**b**) W-11, (**c**) W-12 and (**d**) W-13 samples crystallized at 180 ◦C for 14 h using an aluminosilicate gel precursor of *y*SiO2:1Al2O3:3.5K2O:130H2O where *y* = 1.5, 5, 7 and 10, respectively. The \* marks in (**c**) indicate the presence of the LTL crystalline phase.

**Figure 8.** FESEM images of solids prepared using a precursor hydrogel of *y*SiO2:1Al2O3:3.5K2O: 130H2O at 180 ◦C for 14 h where *y* = (**a**) 1.5 (W-10), (**b**) 5 (W-11), (**c**) 7 (W-12) and (**d**) 10 (W-13).
