In situ monitoring of desilication of MFI-type zeolites in alkaline medium

Abstract

In situ pH and Attenuated Total Reflection (ATR) infrared techniques have been successfully applied in order to gain insights into the dissolution process connected to mesopore formation occurring upon alkaline treatment of ZSM-5 zeolites. Online pH measurements reveal a similar consumption of OH(-) ions in the initial stage of the reaction independent of the Si/Al ratio of the zeolite. In view of the greatly different mesoporosity development, the extraction of polymeric silica entities is anticipated, its structure depending on the framework Si/Al ratio. In agreement, ATR-IR experiments have confirmed dissolution of polymeric silicon-containing species that in the course of the alkaline treatment disintegrate into smaller entities. A direct relation between the type of porosity developed and the process of silicon extraction as measured in the liquid phase cannot be drawn.

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

“…56,57,59 The rate of silica dissolution decreases in the order of K + > Na + > Li + . [58][59][60] This is the result of the lower solvation diameter of K + in basic media, 61 which enhances the adsorption of these cations on the SiO 2 as compared to Na + (ref.…”

Chiral (Salen) Cobalt Complexes Encapsulated in Mesoporous MFI as an Enantioselective Catalyst for Asymmetric Ring Opening of Terminal Epoxides

“…Over the last two decades, salen complexes have been successfully synthesized inside the supercages of X, Y, EMT zeolites [13,14]. However, the pore size and cage shape of microporous zeolites are strictly limited by their crystalline topology (usually \1.5 nm) for other zeolites such as MFI [15][16][17]. It is difficult to synthesize the salen complexes with relatively larger molecular size by the ''shipin-a-bottle'' method.…”

“…Easy synthesis of zeolites with well defined pore size and cage shape still remains as a challenging objective. Compared with microporous zeolites, mesoporous ones have larger pore size and cage, which provides possibilities for trapping larger molecules and more comfortable microenvironment for guest molecules [15][16][17][18][19].…”

Non-Covalent Immobilization of Chiral (Salen) Complexes on HF-treated Mesoporous MFI-type Zeolite for Asymmetric Catalysis

“…13,14 However, the pore size and cage shape of microporous zeolites are strictly limited by their crystalline topology (usually <1.5 nm) for other zeolites such as MFI. [15][16][17] It is difficult to introduce the salen complexes with relatively larger molecular size into the microporous channel of zeolites. The development of simple method to synthesize the zeolites having well defined mesopores still remains as a challenging objective.…”

“…Compared with microporous zeolites, mesoporous ones have larger size pore and cage, which provide possibilities for trapping larger molecules and more comfortable microenvironment for guest molecules. [15][16][17][18][19] In this work, a method to obtain the novel mesoporous MFI structural zeolites with tunable pore size and well defined shape was examined and presented. Our main methodology for synthesis of mesoporous MFI was desilication of microporous MFI-zeolite by HF solution treatment.…”