Synthesis of EU‐1/ZSM‐48 Co‐Crystalline Zeolites from High‐Silica EU‐1 Seeds: Tailoring Phase Proportions and Promoting Long Crystalline‐Phase Stability

Abstract

Abstract A facile, specific, seed‐assisted strategy for the synthesis of EU‐1/ZSM‐48 co‐crystalline zeolites in the presence of hexamethonium ions (HM 2+ ) has been developed. EU‐1/ZSM‐48 co‐crystalline zeolites with various phase proportions, with EU‐1 in the range of 25 wt %–86 wt %, were obtained by adding high‐silica EU‐1 seeds (SiO 2 /Al 2 O 3 ratio of 300) and adjusting the synthesis parameters. Not only can the phase proportions of EU‐1/ZSM‐48 co‐crystalline zeolites be controlled, but also the stability period for co‐crystallization of the two phases can be extended through varying the amount of EU‐1 seeds and the HM 2+ template. Moreover, with the increase of the EU‐1 proportion in the EU‐1/ZSM‐48 co‐crystalline, the framework SiO 2 /Al 2 O 3 ratios of EU‐1 phase promotes steadily. Major differences in acidity and textural properties of the EU‐1/ZSM‐48 co‐crystalline zeolites (Coz) were found with varying phase proportions, due to their distinct topological structures, crystal morphology and asymmetry between the EU‐1 and ZSM‐48 phases. For instance, the EU‐1/ZSM‐48 zeolite containing 75 wt % of EU‐1 (Coz‐75) possesses specific acidity and mesoporous characteristics, showing an excellent catalytic activity and stability in n ‐hexane cracking reaction. Compared to EU‐1, ZSM‐48, and a mechanical mix of the two zeolites (Mix‐75), Coz‐75 resulted in the highest hexane conversion and yields of light olefins, with a propylene yield, in particular, up to 38.3 wt %, which is 6.3 % more than that of the Mix‐75 sample.