Full Compositional Flexibility in the Preparation of Mesoporous MFI Zeolites by Desilication

• Published in: Journal of physical chemistry. C 2011-07, Vol.115 (29), p.14193-14203
• Main Authors: Verboekend, Danny, Mitchell, Sharon, Milina, Maria, Groen, Johan C, Pérez-Ramírez, Javier
• Format: Article
• Language: English
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp201671s

We demonstrate that desilication in alkaline medium is a suitable post-synthetic method to introduce intracrystalline mesoporosity in MFI zeolites independent of the Si/Al ratio in the parent material. By systematic screening of the influence of both base concentration (0.1–1.8 M NaOH) and Si/Al ratio (10–1000) on the properties of the treated zeolites, we reveal that effective mesoporosity introduction (>200 m2 g–1) may be achieved in the Si/Al range of 12–200. The use of descriptors like the “indexed hierarchy factor” and the “desilication efficiency” enable the rational categorization of the solids obtained. The highest desilication efficiencies, estimated by correlating the introduced mesoporosity with the yields after NaOH treatment, are obtained in the previously established Si/Al range of 25–50. We identify the crucial role of a subsequent acid treatment for removing amorphous Al-rich debris from alkaline-treated samples in the case of low Si/Al ratios (