Investigations of the formation of zeolite ZSM-39 (MTN)

Abstract

Crystallization of zeolite ZSM-39 (MTN), a clathrate and silicate analogue of the 17 Å cubic gas hydrate, was examined in a solvent system involving a tetramethylammonium chloride – 1,6-hexanediol deep eutectic mixture and significant amount of water. The crystallization process was followed by powder X-ray diffraction (PXRD), and solid-state nuclear magnetic resonance (SSNMR) techniques involving several nuclei such as 19F, 29Si, and 13C. The results indicate that the crystallization starts from the arrangement of amorphous Si–O–Si species around the tetramethylammonium ions and subsequent formation of the cages in the precursors similar to [51264] cages in the MTN topology. The larger [51264] cages are then connected via the smaller [512] cages containing the fluoride ions to form the final MTN structure. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses show that the crystal growth rates along <100> and <111> directions are roughly the same, suggesting that the (100) and (111) planes have similar stability under the crystallization conditions used. AFM study also shows that the freshly born nuclei on the (100) face are of a height of 2 nm, suggesting a layer by layer growth of the polyhedral crystal.

Acidic medium synthesis of zeolites – an avenue to control the structure-directing power of organic templates

“…Such species are usually observed with 19 F NMR in a chemical shift range between −50 and −80 ppm. 46,47…”

“…It should be noted that F − in SiF 4 has a chemical shift δ ( 19 F) of −162 ppm, 48 while SiF 6 2− , which is often present in the hydrogels for zeolite crystallization, shows a chemical shift δ ( 19 F) of −123 to −128 ppm. 47…”

“…Such species are usually observed with 19 F NMR in a chemical shift range between −50 and −80 ppm. 46,47 The 19 F MAS NMR spectra present a spinning sideband pattern with an isotropic central band at −122.1 ppm (Fig. 3).…”

Deep eutectic solvents for the preparation and post-synthetic modification of metal- and covalent organic frameworks

“…Another appealing development is the use of DESs for the preparation and PSM of other types of crystalline porous materials such as zeolites or nanostructured materials, as highlighted in recent reports. [149][150][151][152][153] For instance, Lin et al investigated the formation of ZSM-39 zeolite with the MTN topology in the tetramethylammonium chloride/1,6-hexanediol DES. 150 They also reported the successful synthesis of ZSM-5 in tetrapropylammonium bromide/pentaerythritol.…”

INVESTIGATION OF “MCM-22”, “ZSM-12 & 35 COMPOSITE”, and “ZEOLITE AL-MORDENITE & ZSM-39 COMPOSITE” CRYSTALS BY ANALYSIS OF CHARACTERIZATION TECHNIQUES

“…Since homogeneous catalysts have the problem of separation in successive reactions, and heterogeneous catalysts have a lower level of contact between the catalyst and the reactant, the strategy of using porous solid catalysts was proposed. This series includes zeolite membranes and zeolites [2] (silicates or aluminum silicates, crystalline mesopores [3,4]), where tetrahedral aluminum and silicon atoms usually surround oxygen atoms. [5]), sulfated oxides such as TiO2, SnO2, and ZrO2 [6,7], heteropoly acids [8], and sulfated carbon [9], which have been developed over the past decade.…”