Tracking the rearrangement of atomic configurations during the conversion of FAU zeolite to CHA zeolite

In order to realize designed synthesis, understanding the formation mechanism of zeolites at an atomic level has long been aspired, but remains challenging due to the fact that the knowledge of atomic configurations of the species formed during the process is limited. We focus on a synthesis system...

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Published inChemical science (Cambridge) Vol. 10; no. 37; pp. 8533 - 8540
Main Authors Muraoka, Koki, Sada, Yuki, Shimojima, Atsushi, Chaikittisilp, Watcharop, Okubo, Tatsuya
Format Journal Article
LanguageEnglish
Published England Royal Society of Chemistry 07.10.2019
Subjects
Aluminates
Aluminum
Catalysis
Chemistry
Computer simulation
Configurations
Conversion
Crystal structure
Monte Carlo simulation
NMR spectroscopy
Silicates
Silicon
Synthesis
Zeolites
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Summary:In order to realize designed synthesis, understanding the formation mechanism of zeolites at an atomic level has long been aspired, but remains challenging due to the fact that the knowledge of atomic configurations of the species formed during the process is limited. We focus on a synthesis system that crystallizes CHA zeolite from FAU zeolite as the sole source of tetrahedral atoms of Si and Al, so that end-to-end characterization can be conducted. Solid-state 29 Si MAS NMR is followed by high-throughput computational modeling to understand how atomic configurations changed during the interzeolite conversion. This reveals that the structural motif commonly found in FAU and CHA is not preserved during the conversion; rather, there is a specific rearrangement of silicates and aluminates within the motif. The atomic configuration of CHA seems to be influenced by that of the starting FAU , considering that CHA synthesized without using FAU results in a random Al distribution. A Metropolis Monte-Carlo simulation combined with a lattice minimization technique reveals that CHA derived from FAU has energetically favorable, biased atomic locations, which could be a result of the atomic configurations of the starting FAU . These results suggest that by choosing the appropriate reactant, Al placement could be designed to enhance the targeted properties of zeolites for catalysis and adsorption.
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These authors contributed equally.
Present address: Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
ISSN:2041-6520
2041-6539
DOI:10.1039/C9SC02773D