Synthesis of hierarchical lamellar MFI zeolites with sequential intergrowth influenced by synthetic gel composition

• Published in: Microporous and mesoporous materials 2019-02, Vol.275, p.31-41
• Main Authors: Emdadi, Laleh, Tran, Dat T., Schulman, Emily, Wei, Lu, Shang, Wenjin, Chen, Huiyong, Liu, Dongxia
• Format: Article
• Language: English
• Subjects: 2D zeolite; Acid site accessibility; Hierarchical zeolite; Intergrowth; Mesoporosity
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2018.08.007

Hierarchical lamellar zeolites, comprised of both micro- and mesoporosity, afford high active site accessibility and mass transport in processing of bulky molecules. Here, we report the synthesis of hierarchical lamellar MFI zeolites with sequential intergrowth that is induced by composition variation in the standard recipe of 100SiO2/0.5Al2O3/3C22-6-6/18.5Na2O/4000H2O, where C22-6-6 stands for the diquaternary ammonium surfactant ([C22H45N+(CH3)2C6H12N+(CH3)2C6H13]Br−2) template. The influences of C22-6-6 concentration, alkalinity, and aluminum amount on the intergrowth of hierarchical lamellar MFI zeolites were investigated. The consequences of intergrowth on mesoporosity were analyzed. In all studied synthesis conditions except for very low alkalinity, hierarchical lamellar MFI zeolites were successfully crystallized. The increasing template concentration in the synthesis gel resulted in an increase in intergrowth and thus mesoporsotiy in the hierarchical MFI products. The increasing alkalinity led to an increase and then a decrease in mesoporosity in the hierarchical MFI products, which reflects the same trend in intergrowth in the hydrothermal synthesis process. The aluminum concentration, however, did not significantly affect the intergrowth and mesoporosity of the resultant hierarchical MFI zeolites. The sequential intergrowth achieved by simple variation in the synthesis composition for lamellar MFI zeolites resulted in higher structure hierarchy, mesoporosity, and acid site accessibility in one-step. [Display omitted] •Hierarchical lamellar MFI zeolites were synthesized in one-step.•Intergrowth enhanced mesoporosity in hierarchical lamellar MFI zeolites.•Intergrowth increased with increasing surfactant template content in synthetic gel.•Intergrowth increased and then decreased with alkalinity in synthetic gel.•Aluminum content in synthetic gel did not influence intergrowth noticeably.