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Insight into the dissolution-crystallization strategy towards macro/meso/microporous Silicalite-1 zeolites and their performance in the Beckmann rearrangement of cyclohexanone oxime

Abstract

Hierarchically macro/meso/microporous Silicalite-1 single crystals were successfully fabricated based on an in situ dissolution-crystallization strategy without the assistance of secondary templates and the corresponding fabrication mechanism was systematically investigated in this study. Mesoporous silica spheres (MSS) precursors could provide quasi “space-occupying” effect to construct the intracrystalline macropores while functioning as silica source. Various factors including amount of tetrapropylammonium hydroxide, crystallization temperature and initial water content in synthesis mixtures were investigated considering their distinct effects on the dissolution and crystallization processes. It has been found that the intracrystalline macropores could only formed via a precise controlling of velocity difference between the outside-in dissolution of MSS and the crystallization of Silicalite-1 zeolite. Based on the recognition of the fabrication mechanism, a further modified Silicalite-1 with much richer porosity (meso-/macropore volume was increased from 0.15 to 0.26 cm3 g-1) was synthesized successfully. Owing to the introduction of macropores and mesopores, the concentration and accessibility of active hydroxyl groups as well as the diffusional properties over hierarchical Silicalite-1 were both significantly enhanced and improved. And therefore, the hierarchical samples showed higher catalytic activities and superior catalyst lifetime in the Beckmann rearrangement of cyclohexanone oxime compared to conventional microporous Silicalite-1. The present study contributes a new understanding of the evolution mechanism of amorphous precursors to hierarchical zeolites in a secondary-template-free system, and that is of great significance for the development of direct fabrication methods towards hierarchical zeolites and the Beckmann rearrangement reaction.

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Publication details

The article was received on 02 May 2018, accepted on 27 Jul 2018 and first published on 30 Jul 2018


Article type: Paper
DOI: 10.1039/C8CY00885J
Citation: Catal. Sci. Technol., 2018, Accepted Manuscript
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    Insight into the dissolution-crystallization strategy towards macro/meso/microporous Silicalite-1 zeolites and their performance in the Beckmann rearrangement of cyclohexanone oxime

    Y. Zhang, L. Xu, J. Zhang, P. Li, Y. Yuan, H. Guo, X. Zhang and L. Xu, Catal. Sci. Technol., 2018, Accepted Manuscript , DOI: 10.1039/C8CY00885J

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