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Theses

Hollow Beta zeolites : synthesis and impact of the hollow morphology on diffusion and catalysis

Abstract : Hollow zeolite single crystals have received particular interest in catalysis. The presence of a large cavity in these model zeolites enables the study of diffusional limitation in Catalysis. The cavity also enables the encapsulation of metal nanoparticles. However, their synthesis requires specific structural characteristics and it has been limited for long to zeolites with the MFI structure. The objective of this PhD work was to investigate the synthesis of hollow Beta zeolites (*BEA framework type) and study the impact of the hollow morphology on molecular diffusion and catalysis. Two different strategies have been envisaged: a dissolution/recrystallization approach using CIT-6, a zincosilicate with the same *BEA topology and a selective desilication route. Pt nanoparticles encapsulated in hollow crystals obtained from CIT-6 showed remarkable size-selectivity in the hydrogenation of aromatics. The effect of the hollow morphology in molecular diffusion was studied using the ZLC technique; the characteristic diffusion time of the hollow morphology was reduced by 30-83% compared to the corresponding bulk zeolite. Despite that, the hollow structure had no influence on the catalytic activities for the hydroisomerization of n-C16 and for the cracking of cyclohexane. The presence/absence of diffusional limitation is discussed
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https://tel.archives-ouvertes.fr/tel-02407012
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Submitted on : Thursday, December 12, 2019 - 12:20:26 PM
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  • HAL Id : tel-02407012, version 1

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Ana Rita Morgado Prates. Hollow Beta zeolites : synthesis and impact of the hollow morphology on diffusion and catalysis. Catalysis. Université de Lyon, 2019. English. ⟨NNT : 2019LYSE1155⟩. ⟨tel-02407012⟩

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