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Mesoporous silica scaffolds as precursor to drive the formation of hierarchical SAPO-34 with tunable acid properties

Mesoporous silica scaffolds as precursor to drive the formation of hierarchical SAPO-34 with tunable acid properties
Mesoporous silica scaffolds as precursor to drive the formation of hierarchical SAPO-34 with tunable acid properties
Using a distinctive bottom-up approach, hierarchical SAPO-34 has been synthesized using CTAB encapsulated within ordered mesoporous silica (MCM-41) that serves as both the silicon source and mesoporogen. The structural and textural properties of the hierarchical SAPO-34 were contrasted against its microporous analogue, and the nature, strength and accessibility of the Brønsted acid sites were studied using a range of physicochemical characterization tools; notably probe-based FTIR and solid-state (SS) MAS NMR. Whilst CO was used to study the acid properties of hierarchical SAPO-34, bulkier molecular probes (including pyridine, 2,4,6-trimethylpyridine and 2,6-di-tert-butylpyridine) allowed particular insight into the enhanced accessibility of the acid sites. The activity of the hierarchical SAPO-34 catalyst was evaluated in the industrially-relevant, acid-catalysed Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam, under vapor-phase conditions. These catalytic investigations revealed a significant enhancement in the yield of ε-caprolactam using our hierarchical SAPO-34 catalyst compared to SAPO-34, MCM-41, or a mechanical mixture of these two phases. The results highlight the merits of our design strategy for facilitating enhanced mass transfer, whilst retaining favorable acid site characteristics.
0947-6539
Raja, Robert
74faf442-38a6-4ac1-84f9-b3c039cb392b
Miletto, Ivana
9a3fe0ee-6afd-4e72-abff-8e83a9114ae9
Paul, Geo
fe93c674-eedd-4eda-8c84-190bc5b1687f
Chapman, Stephanie
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Gatti, Giorgio
a086db60-be42-46c2-a3a7-90522afa691f
Marchese, Leonardo
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Gianotti, Enrica
2496d8d3-780f-4fe0-a43e-147e68331078
Raja, Robert
74faf442-38a6-4ac1-84f9-b3c039cb392b
Miletto, Ivana
9a3fe0ee-6afd-4e72-abff-8e83a9114ae9
Paul, Geo
fe93c674-eedd-4eda-8c84-190bc5b1687f
Chapman, Stephanie
02fa6ac4-c0e7-4cd3-8ffb-bf1c88cbfd45
Gatti, Giorgio
a086db60-be42-46c2-a3a7-90522afa691f
Marchese, Leonardo
684a36ec-9847-4604-82e7-71234cd44090
Gianotti, Enrica
2496d8d3-780f-4fe0-a43e-147e68331078

Raja, Robert, Miletto, Ivana, Paul, Geo, Chapman, Stephanie, Gatti, Giorgio, Marchese, Leonardo and Gianotti, Enrica (2017) Mesoporous silica scaffolds as precursor to drive the formation of hierarchical SAPO-34 with tunable acid properties. Chemistry - A European Journal, [chem.201701978]. (doi:10.1002/chem.201701978).

Record type: Article

Abstract

Using a distinctive bottom-up approach, hierarchical SAPO-34 has been synthesized using CTAB encapsulated within ordered mesoporous silica (MCM-41) that serves as both the silicon source and mesoporogen. The structural and textural properties of the hierarchical SAPO-34 were contrasted against its microporous analogue, and the nature, strength and accessibility of the Brønsted acid sites were studied using a range of physicochemical characterization tools; notably probe-based FTIR and solid-state (SS) MAS NMR. Whilst CO was used to study the acid properties of hierarchical SAPO-34, bulkier molecular probes (including pyridine, 2,4,6-trimethylpyridine and 2,6-di-tert-butylpyridine) allowed particular insight into the enhanced accessibility of the acid sites. The activity of the hierarchical SAPO-34 catalyst was evaluated in the industrially-relevant, acid-catalysed Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam, under vapor-phase conditions. These catalytic investigations revealed a significant enhancement in the yield of ε-caprolactam using our hierarchical SAPO-34 catalyst compared to SAPO-34, MCM-41, or a mechanical mixture of these two phases. The results highlight the merits of our design strategy for facilitating enhanced mass transfer, whilst retaining favorable acid site characteristics.

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Accepted/In Press date: 30 May 2017
e-pub ahead of print date: 2 June 2017
Organisations: Chemistry, FIMS, Southampton Marine & Maritime Institute

Identifiers

Local EPrints ID: 411462
URI: http://eprints.soton.ac.uk/id/eprint/411462
ISSN: 0947-6539
PURE UUID: df5cb7ff-8840-4989-973f-88ae53331a7e
ORCID for Robert Raja: ORCID iD orcid.org/0000-0002-4161-7053

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Date deposited: 20 Jun 2017 16:31
Last modified: 18 Feb 2021 17:07

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Contributors

Author: Robert Raja ORCID iD
Author: Ivana Miletto
Author: Geo Paul
Author: Stephanie Chapman
Author: Giorgio Gatti
Author: Leonardo Marchese
Author: Enrica Gianotti

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