Synthesis of ZSM-5 from natural mordenite from Spain

Zeolite ZSM-5 has been synthesized using natural mordenite sourced from the San José-Los Escullos-Cabo de Gata deposit in southeast of Spain. The final pure ZSM-5 was achieved without the need of calcination of the natural mordenite through an inter-zeolite transformation being the adjustment of the Si/Al ratio the key factor. The Si/Al ratio of the natural mordenite was modified through two main methods: (i) dealumination under acidic conditions and (ii) the addition of an extra silica source. Dealumination process adds the advantage of eliminating the impurities present in the initial natural mordenite. ZSM-5 with over 88 % crystallinity was produced under hydrothermal synthesis conditions at 190 °C for 48 h using NH₄OH as the alkalinity source with coffin shape particles showing short b-axis ranging from 90 to 200 nm. Similarly, ZSM-5 with over 78 % crystallinity was obtained with NaOH as the alkalinity source at 190 °C for 48 h, however, the particles are irregular-shaped of around 160–260 nm in size. In the second approach, despite the presence of impurities of Fe, highly crystalline (over 100 % crystallinity) ZSM-5 is produced, once again with well-shaped coffin shaped crystals using NH₄OH yet larger, with a b-axis ranging from 200 to 300 nm and irregular shaped ZSM-5 using NaOH.