Evolution of Surface Morphology with Introduction of Stacking Faults in Zeolites

Abstract

This paper sets out to try to determine some of the nanoscopic details of template action in zeolites. The problem has been addressed by monitoring the effects of competitive templating using, in particular, atomic force microscopy and high-resolution scanning electron microscopy. Using these techniques, it is possible to determine the subtle crystal growth changes that occur as a result of altering the concentration of these competitive templating agents. This work concerns the two important intergrowth systems MFI-MEL and FAU-EMT. It was found that some organic templating agents provide much greater structure-directing specificity. So much so in the case of the MFI-MEL system that a 2 mol% doping with the highly specific tetrapropylammonium cation drastically changes the fundamental growth processes. Furthermore, the effect of template crowding is shown to reduce specificity. This work shows how extensive frustrated intergrowth structures can still be accommodated within a nominal zeolite single crystal.

Study of template interactions in MFI and MEL zeolites using quantum methods

“…This outcome is in agreement with experimental findings that show that TPA is very efficient as SDA for MFI formation [26]. Conversely, TBA sp conformation is more populated, suggesting that TBA is a good MEL SDA in accordance with experimental works [27,28]; however, more energy would be required to populate TBAa to get MEL2 or MFI. In the case of MEL only half of the population is necessary.…”

“…If TPA is used as template, MFI/TPAa is the most stable complex, followed by MEL1/TPAsp and MEL2/TPAa. Then, TPA favored more the formation of MFI than MEL, as it has been experimentally reported [27,28,32]. Nevertheless, for Z/TBA systems, the average stability order (|DE(MFI)| > |-DE(MEL)|) is similar to those of Refs.…”

“…Because TBA angular conformation is less stable, as mentioned in the last Section, MEL is favored over MFI framework. However, TBA does not lead exclusively to the formation of MEL, because MFI have been synthetized by varying the experimental conditions [26,27,29] and intergrowths may be also observed [9,28].…”

Assemblies of Mesoporous FAU‐Type Zeolite Nanosheets

“…NaX-R-cal crystals have a compact octahedral shape which is typical for zeolite X. [27] In contrast, NaX-T-cal consists of ball-shaped house-of-cardslike nanosheet assemblies. These nanosheet balls have a larger diameter (ca.…”

Mesoporöse Nanoschichtaggregate vom Zeolithtyp FAU

“…NaX-R-cal-Kristalle besitzen eine kompakte oktaedrische Morphologie, die typisch für Zeolith X [27] ist. NaX-R-cal-Kristalle besitzen eine kompakte oktaedrische Morphologie, die typisch für Zeolith X [27] ist.…”