Insight into Three‐Coordinate Aluminum Species on Ethanol‐to‐Olefin Conversion over ZSM‐5 Zeolites

Wang, Zichun; O’Dell, Luke A.; Zeng, Xin; Liu, Can; Zhao, Shufang; Zhang, Wenwen; Gaborieau, Marianne; Jiang, Yijiao; Huang, Jun

doi:10.1002/ange.201910987

Cited by 11 publications

(10 citation statements)

References 68 publications

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“…Octahedrally coordinated Al atoms observed in these samples exposed to ambient atmosphere are in fact isolated Al species able to bind H2O molecules from air moisture. 18,53,54 This again pointed towards the fact that NHSG leads to highly homogeneous Si-Al mixing.…”

Section: Resultsmentioning

confidence: 86%

“…Finally, the selectivity improvement for p_Me, p_PhCH2 and b_Xy might be explained by the marked lowering the B/L ratio in the case of the hybrid samples: catalysts with more abundant strong Lewis acid sites have been shown to produce ethylene with higher selectivity. 12,38,54,58 200 To confirm that the organic groups presence (hydrophilicity/hydrophobicity) had only negligible direct effect on catalytic performance, p_PhCH2 was calcined at 500 °C in order to completely remove organic groups and the resulting catalyst (p_PhCH2-500) was tested again in ethanol dehydration. As a reference, 16Si-1Al was also re-calcined and re-tested (compare samples p_PhCH2-500 and 16Si-1Al-500).…”

Section: Resultsmentioning

confidence: 99%

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Non-hydrolytic sol–gel route to a family of hybrid mesoporous aluminosilicate ethanol dehydration catalysts

et al. 2021

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Organic-inorganic hybrid materials are nowadays intensely studied for potential applications in heterogeneous catalysis because their properties and catalytic behavior differ from pristine inorganic counterparts. The organic groups at the catalyst surface can modify not only its hydrophilicity, but also acidity, hydrothermal stability, porosity, etc. In some cases, such properties alteration leads to improved catalytic performance in terms of activity, selectivity, or stability. However, the choice of organic groups stays relatively narrow, as most reports focus on pendant methyl groups. Here, a series of mesoporous hybrid aluminosilicate materials containing various organic groups was prepared in one pot by nonhydrolytic sol-gel (NHSG). Both aromatic and aliphatic, pendant and bridging organic groups were incorporated. The presence of the organic groups in the bulk and at the outermost surface of the materials was verified by solid-state NMR and ToF-SIMS, respectively.Aluminum is mostly incorporated in tetrahedral coordination in the hybrid silica matrix. The organically modified mesoporous aluminosilicate samples were tested as catalysts in the gas phase ethanol dehydration (which relies on solid acids) and most of them outperformed the purely inorganic catalyst benchmark. While a direct influence of surface hydrophilicity or hydrophobicity (as probed by water sorption and water contact angle measurements) appeared unlikely, characterization of acidity (IR-pyridine) revealed that the improved performance for hybrid catalysts can be correlated with a modification of the acidic properties. In turn, acidity is determined by the quality of the dispersion of Al centers in the form of isolated sites in the hybrid silica matrix. All in all, this study establishes a "ranking" for a variety of organic groups in terms of their effect on gas-phase ethanol dehydration to ethylene; ethylene yield decreases in this order: bridging xylylene ≈ pendant methyl > pendant benzyl > bridging methylene ≈ inorganic benchmark (no organic groups) > bridging ethylene.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Non-hydrolytic sol–gel route to a family of hybrid mesoporous aluminosilicate ethanol dehydration catalysts

et al. 2021

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“…In order to investigate the effect of NTP exposure on the migration of aluminium from the framework, resulting in extra framework aluminium (EFAl), which are Lewis acid sites (Wang et al, 2019;Li and Pidko, 2019), in-situ IR spectroscopy of pyridine adsorbed on thermal and NTP activated MS-13X was performed. In addition, the analysis of the IR spectra of the OH groups were investigated to get more information about the nature of the acid sites.…”

Section: Surface and Bulk Properties Of Activated And Regenerated Ms-13xmentioning

confidence: 99%

Effect of non-thermal plasma in the activation and regeneration of 13X zeolite for enhanced VOC elimination by cycled storage and discharge process

Veerapandian

Giraudon²,

Morin³

et al. 2022

Journal of Cleaner Production

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“…[43][44][45] Bifunctional Brønsted-Lewis acidic zeolites are typically prepared by framework dealumination or Al exchange to introduce Lewis acidic extra-framework Al (EFAl) species. 33,46 However, these species can easily leach out in liquid-phase reactions, resulting in severe activity loss. 3,47 As an example, the concerted action of BAS and LAS is proposed for the efficient conversion of glyceraldehyde to alkyl lactates, however, the reuse of De-Al-HY causes a severe drop in activity and selectivity, while SA/50 exhibits similar activity before and after reuse under the same conditions (Fig.…”

Section: Acidity Enhancement and Efficient Biomass Conversion Using Al V -Enriched Asasmentioning

confidence: 99%

Pentacoordinated Aluminum Species: New Frontier for Tailoring Acidity-Enhanced Silica–Alumina Catalysts

et al. 2020

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CONSPECTUS: Silica-alumina catalysts, including zeolites and amorphous silica-aluminas (ASAs), are amongst the most widely used solid acid catalysts and supports to produce petrochemicals, fine chemicals, and renewable energy. The coordination, distribution, and interactions of aluminum in ASAs have an enormous impact on their acidic properties and catalytic performance. Unsaturated tetracoordinated aluminum (Al IV ) species are commonly accepted as the key sites in generating catalytically active Brønsted acid sites (BASs) in silica-alumina catalysts.Extensive efforts focus on increasing the concentration of Al IV as the main route to enhance their Brønsted acidity for efficient catalysis. However, increasing the Al IV concentration either weakens the acid strength in zeolites or lowers Brønsted acidity in ASAs at high Al/Si ratios, impeding acidity enhancement of these popular catalysts."Penta-coordinated aluminum (Al V ) species" are potential unsaturated Al species like Al IV but rarely observed in silica-aluminas, and thus, are widely considered unavailable for BAS formation or surface reactions. In this Account, we will describe novel strategies for the controlled synthesis of Al V -enriched ASAs and corresponding supported metal nanocatalysts using flame spray pyrolysis (FSP) techniques and highlight the contribution of Al V species in acidity enhancement, together with their structure-activity relationship in the conversion of biomass-derived compounds into valuable chemicals. Using various in situ and advanced 2D solid-state NMR (SSNMR) experiments, the studies of the acidic properties and local structure of Al V -enriched ASAs reveal that Al V species can highly populate on ASA surfaces, promote BASs formation and facilitate adaptable tuning of BASs from moderate to zeolitic strength by synergy with neighboring Al species. Moreover, the BASs with enhanced acidity can work jointly with surface Lewis acid sites or metal active species for bifunctional catalysis on Al V -enriched ASAs. Compared to zeolites, these Al V -enriched ASAs are highly active in acid-catalyzed biomass conversion, including 3 alcohol dehydration and sugar conversion reactions, as well as in promoting the performance of supported metal catalysts in chemoselective hydrogenation of aromatic ketones. These new insights provide a state-of-the-art strategy for strongly enhancing the acidity of these popular silica-alumina catalysts, which offers an interesting potential for a wide range of acid and multifunctional catalysis.

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Insight into Three‐Coordinate Aluminum Species on Ethanol‐to‐Olefin Conversion over ZSM‐5 Zeolites

Cited by 11 publications

References 68 publications

Non-hydrolytic sol–gel route to a family of hybrid mesoporous aluminosilicate ethanol dehydration catalysts

Non-hydrolytic sol–gel route to a family of hybrid mesoporous aluminosilicate ethanol dehydration catalysts

Effect of non-thermal plasma in the activation and regeneration of 13X zeolite for enhanced VOC elimination by cycled storage and discharge process

Pentacoordinated Aluminum Species: New Frontier for Tailoring Acidity-Enhanced Silica–Alumina Catalysts

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