Synthesis of EU-1/ZSM-48 Co-crystalline Zeolite by High Silica EU-1 Seeds: Tailoring Phase Proportions and Promoting Long Crystalline Phase Stability.

A facile, specific, seed-assisted strategy for the synthesis of EU-1/ZSM-48 co-crystalline zeolites in the presence of hexamethonium ions (HM2+) 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 (SiO2/Al2O3 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 HM2+ template. Moreover, with the increase of the EU-1 proportion in the EU-1/ZSM-48 co-crystalline, the framework SiO2/Al2O3 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.