Enhanced Selectivity and Stability of Finned Ferrierite Catalysts in Butene Isomerization

Rimer, Jeffrey D.; Dai, Heng; Lee, ChoongSze; Liu, Wen; Yang, Taimin; Claret, Jakob; Zou, Xiaodong; Dauenhauer, Paul J.; Li, Xiujie

doi:10.1002/ange.202113077

“…Alternatively, solids extracted from the identical growth mixture without seeds are a non-zeolite crystalline phase (Figure S5). It is possible that the rough protrusions have an FAU crystal structure, analogous to finned zeolites where the fins grow epitaxially on surfaces of zeolite seeds. , Conversely, these features may be defects with a similar (unidentified) structure as the non-seeded synthesis. It is apparent, however, that growth of the FAU crystal substrate is highly dependent upon the Si/Al ratio of the growth medium.…”

Section: Resultsmentioning

confidence: 99%

In Situ Imaging of Faujasite Surface Growth Reveals Unique Pathways of Zeolite Crystallization

Jain

¹

,

Niu

²

,

Choudhary

³

et al. 2023

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Zeolite crystallization occurs by complex processes involving a variety of possible mechanisms. The sol gel media used to prepare zeolites leads to heterogeneous mixtures of solution and solid states with diverse solute species. At later stages of zeolite synthesis when growth occurs predominantly from solution, classical two-dimensional nucleation and spreading of layers on crystal surfaces via the addition of soluble species is the dominant pathway. At earlier stages, these processes occur in parallel with nonclassical pathways involving crystallization by particle attachment (CPA). The relative roles of solution- and solid-state species in zeolite crystallization have been a subject of debate. Here, we investigate the growth mechanism of a commercially relevant zeolite, faujasite (FAU). In situ atomic force microscopy (AFM) measurements reveal that supernatant solutions extracted from a conventional FAU synthesis at various times do not result in growth, indicating that FAU growth predominantly occurs from the solid state through a disorder-to-order transition of amorphous precursors. Elemental analysis shows that supernatant solutions are significantly more siliceous than both the original growth mixture and the FAU zeolite product; however, in situ AFM studies using a dilute clear solution with a lower Si/Al ratio revealed three-dimensional growth of surfaces that is distinct from layer-by-layer and CPA pathways. This unique mechanism of growth differs from those observed in studies of other zeolites. Given that relatively few zeolite frameworks have been the subject of mechanistic investigation by in situ techniques, these observations of FAU crystallization raise the question whether its growth pathway is characteristic of other zeolite structures.

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“…The same procedure was performed for the as-synthesized Core sample as a reference using a protocol similar to the preparation of finned zeolites. [27] We first tested the annealing process on the Core, which involves the suspension of zeolite crystals in an alkaline solution (pH 11) containing a small quantity of silica (close to the solubility of zeolite beta) and an organic structure-directing agent (tetraethylammonium, TEA). This solution was hydrothermally treated at 170 °C for different times.…”

Section: Resultsmentioning

confidence: 99%

Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

Han

¹

,

Linares

²

,

Terlier

³

et al. 2022

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We report a method to prepare core-shell zeolite beta (*BEA) with an aluminous core and an epitaxial Si-rich shell. This method capitalizes on the inherent defects in *BEA crystals to simultaneously passivate acid sites on external surfaces and increase intracrystalline mesoporosity through facile post-hydrothermal synthesis modification in alkaline media. This process creates more hydrophobic materials by reducing silanol defects and enriching the shell in silica via a combination of dealumination and the relocation of silica from the core to the shell during intracrystalline mesopore formation. The catalytic consequences of *BEA core-shells relative to conventional analogues were tested using the biomass conversion of levulinic acid and n-butanol to n-butyl levulinate as a benchmark reaction. Our findings reveal that siliceous shells and intracrystalline mesopores synergistically enhance the performance of *BEA catalysts.

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“…Additional acid site characterization using pyridine-FT-IR revealed that Core, CS, and CSA samples have an approximate 70 : 30 split between Brønsted acid sites (BAS) and Lewis acid sites (LAS), whereas CA has slightly higher BAS density (76 %). Solid state 27 Al NMR analysis reveals that the percentage of extra-framework Al (EFAl) falls within a narrow range for all samples (10-12 %), with the exception of CS that has a slightly higher EFAl content (ca. 19 %).…”

Section: Samplementioning

confidence: 99%

Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

Han

¹

,

Linares

²

,

Terlier

³

et al. 2022

View full text Add to dashboard Cite

We report a method to prepare core-shell zeolite beta (*BEA) with an aluminous core and an epitaxial Si-rich shell. This method capitalizes on the inherent defects in *BEA crystals to simultaneously passivate acid sites on external surfaces and increase intracrystalline mesoporosity through facile post-hydrothermal synthesis modification in alkaline media. This process creates more hydrophobic materials by reducing silanol defects and enriching the shell in silica via a combination of dealumination and the relocation of silica from the core to the shell during intracrystalline mesopore formation. The catalytic consequences of *BEA core-shells relative to conventional analogues were tested using the biomass conversion of levulinic acid and n-butanol to n-butyl levulinate as a benchmark reaction. Our findings reveal that siliceous shells and intracrystalline mesopores synergistically enhance the performance of *BEA catalysts.

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Enhanced Selectivity and Stability of Finned Ferrierite Catalysts in Butene Isomerization

Cited by 9 publications

References 74 publications

In Situ Imaging of Faujasite Surface Growth Reveals Unique Pathways of Zeolite Crystallization

In Situ Imaging of Faujasite Surface Growth Reveals Unique Pathways of Zeolite Crystallization

Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

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