Atomic Force Microscopy and High Resolution Scanning Electron Microscopy Investigation of Zeolite A Crystal Growth. Part 2: In Presence of Organic Additives

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe nanoscopic details of the crystal growth of zeolite A in the presence of the organic modifiers diethanolmaine (DEA) and triethanolamine (TEA) has been determined using a combination of atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM) coupled with Monte Carlo simulations. Crystallization of zeolite A in the presence of TEA was faster than when the growing solution contained DEA. In addition the morphology of the final zeolite A crystals depended on the type of organic molecule, with TEA producing crystals bound only by {100} facets and DEA leading to the formation of relatively large {110} faces. These features can be explained in terms of the relative Si/Al in the growing medium and its control due to the different affinity of the organic molecules toAl. In addition, synthesis performed at 90 °C showed the appearance of {211} facets. Careful review of the HRSEM and AFM images, in addition to comparison with the MC simulations reveal that these are in fact pseudo-facets, product of the slow dissolution of the metastable zeolite A crystals. This proves that the final habit of the LTA crystals can be governed by very small changes of saturation of the growing medium and a control of this paremeter can prove advantageous when designing crystals for industrial applications.

Database of Computation-Ready 2D Zeolitic Slabs

“…The resulting pure silica crystal was rounded while their Si/Al = 1 crystal was cubic . Therefore, their predicted Si/Al = 1 crystal morphology resembles that of most experimental crystals. − Although the surface energies of our siliceous slabs give different relative surface energies than those obtained by Gren et al for aluminosilicates, the structure of the low energy surfaces found by Gren et al and the surfaces from our calculations are very similar (see Figure S7). The materials shown in Figures and are all aluminosilicates, but those in Figure generally have a higher Si:Al ratio than those in Figure .…”

Local and Average Structural Changes in Zeolite A upon Ion Exchange

“…A variety of crystallite shapes and sizes can be observed, somewhere in between cubic and spherical and ranging from 122-354 nm. The visibly larger crystals with well-defined edges display the typical cubic morphology of LTA zeolites [42,43]. However, the low temperature conditions employed in this synthesis appear to slow down crystal growth, instead favouring nucleation in the initial stages [44].…”

Advances in theory and their application within the field of zeolite chemistry

“…In a study of the crystal growth of zeolite L, the parameters of the Monte Carlo simulations were tuned to obtain a good correspondence between the simulated and the observed crystal surface and aspect ratio of the surface. 70 61 For the crystallization of zeolite A in absence of organic additives, Monte Carlo simulations show that the sharpness of the terrace corners is controlled by subtle changes in supersaturation.…”