THESIS OF Céline Pagis*, 2019 Yves Chauvin PRIZE
Zeolites, inorganic crystallized materials containing nanometric pores and channels, are capable of trapping various chemical substances or catalyzing numerous reactions. These distinctive properties make them ideal materials for a large number of industrial processes. However, during chemical reactions, the nanometric size of the channels (< 2 nm) limits molecule diffusion, affecting reaction speeds and reducing the useful fraction of each crystal. To counter this phenomenon, generating additional porosity amounts to creating “highways”, thereby improving molecule flow.
This PhD thesis was conducted using faujasite zeolite (FAU) to explore synthesis routes leading to a new architecture, and more precisely to produce a zeolite in which the crystals, named “nanoboxes”, have a single internal cavity(1), with some major associated advantages:
• crystal size and structure maintained,
• nanometric dimensions of the wall making it possible to improve molecule diffusion within the crystal,
• creation of a favored molecule storage zone.
Two synthesis methods were developed (figure): the 1st consists in agglomerating zeolite nanocrystals to form hollow capsules, and the 2nd in preferentially
dissolving the center of each crystal, thereby creating the internal cavity. Following the evaluation of the diffusional and catalytic properties of these new
materials, a beneficial effect in terms of reduction in their characteristic diffusion length was demonstrated on their activity and their catalytic efficiency(2).
This new approach paves the way for a greater understanding of the impact of structural zeolite parameters on molecule diffusion within them, with a view to improving this phenomenon.
*Thesis entitled "Synthesis and catalytic evaluation of hollow zeolite Y crystals"
(1) C. Pagis, A. R. Prates, D. Farrusseng, N. Bats, A. Tuel, Chem. Mater. 28 (2016) 5205-5223
DOI : 10.1021/acs.chemmater.6b02172
(2) C. Pagis, F. Meunier, Y. Schuurman, A. Tuel, M. Dodin, R. Martinez Franco, D. Farrusseng, ChemCatChem 10 (2018) 4525-4529
DOI : 10.1002/cctc.201801225