Synthesis of high-silica EU-1 zeolite in the presence of hexamethonium ions: A seeded approach for inhibiting ZSM-48

A seeded approach was developed to synthesize high-silica EU-1 zeolite via inhibiting the co-crystallization of ZSM-48 in the presence of hexamethonium (HM) ions. A systematic study was carried out to determine factors such as seed content and SiO2/Al2O3 ratio, which influenced the crystallization of high-silica EU-1 and transformation of EU-1 into ZSM-48. Using EU-1 seeds, not only well-crystallized pure EU-1 zeolites with SiO2/Al2O3 ratios more than 500 were synthesized, but also the co-crystalline of ZSM-48/EU-1 or pure ZSM-48 was obtained in control from silica-rich mixture gels. Furthermore, the kinetic features of the seeded synthesis of EU-1 zeolites with SiO2/Al2O3 ratios of 55, 190, and 500 were examined. It was found that seeds played crucial roles in the decrease of apparent activation energy of EU-1 nucleation and inhibiting the transformation of EU-1 into ZSM-48. The HM and Al species performed synergistic roles to inhibit the formation ZSM-48 during high-silica EU-1 nucleation and crystal growth.

Graphical abstractBy seeded approach, pure EU-1 with SiO2/Al2O3 > 240 were synthesized in HM system and the co-crystalline of ZSM-48/EU-1 or pure ZSM-48 was also tunable.Figure optionsDownload full-size imageDownload high-quality image (77 K)Download as PowerPoint slideHighlights► A seeded approach to synthesize of very high-silica EU-1 in HM system. ► Control of high- silica EU-1, co-crystalline of ZSM-48/EU-1 and ZSM-48. ► Role of seeds to reduce the Ea of EU-1 nucleation and inhibit ZSM-48 phase. ► HM and Al from seeds performed synergy in the crystallization of silica-rich gels.