Enhancement of Activity and Selectivity in Acid‐Catalyzed Reactions by Dealuminated Hierarchical Zeolites

Sazama, Petr; Sobalı́k, Zdenĕk; Dědeček, Jiřı́; Jakubec, Ivo; Pârvulescu, Vasile I.; Bastl, Zdeněk; Rathouský, Jiřı́; Jirglová, Hana

doi:10.1002/anie.201206557

Cited by 60 publications

(43 citation statements)

References 19 publications

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“…Pérez-Ramírez et al found that the mesoporosity of hierarchical zeolites can be tailored by partial detemplation of zeolites followed by desilication in alkaline medium. 143 In addition to the above demetallization methods, an irradiation route was developed by Valtchev et al to prepare hierarchical ZSM-5 zeolite with uniform parallel macropores that extended through the entire crystal. 142 Similar to dealumination, desilication inevitably modulates the framework Si/Al ratios; however, in this case it resulted in decreased Si/Al ratios.…”

Section: Desilicationmentioning

confidence: 99%

Tailoring and visualizing the pore architecture of hierarchical zeolites

et al. 2015

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Recently the concept of hierarchical zeolites invoked more explicit attention to enhanced accessibility of zeolites. By realizing additional meso-/macroporosity with the intrinsic microporosity of zeolites, a hierarchical pore system arises which facilitates mass transport while maintaining the zeolite shape selectivity. A great number of synthesis strategies have been developed for tailoring the pore architecture of hierarchical zeolites. In this review, we give a general overview of different synthesis methods for introduction of additional porosity. Advantages and limitations of these different synthesis approaches are addressed. The assessment of pore structure is essential to build the link between the zeolite pore structure and its functionality. A variety of 2D and 3D microscopy techniques are crucial to visualize the hierarchical pore structure, providing unique and comprehensive information that, however, should be linked to the results of bulk characterization techniques as much as possible. The microscopy techniques are classified and discussed according to the different probes used, such as optical light, X-rays and electrons. Representative work is reviewed to elucidate the capability of each technique and their drawbacks.

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Section: Desilicationmentioning

confidence: 99%

Tailoring and visualizing the pore architecture of hierarchical zeolites

et al. 2015

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“…Conversely, the tetrahedral Al EF species formed during zeolite desilication in alkaline media are mobile and therefore exhibit a narrow symmetrical signal, [7] and Al EF species created upon steaming show an octahedral Al signal or are NMR-invisible.…”

Section: Samplementioning

confidence: 99%

“…Values of d i of around 60 ppm are typical for AlO 4 À tetrahedra in a zeolite environment. [6] The significant broad- Conversely, the tetrahedral Al EF species formed during zeolite desilication in alkaline media are mobile and therefore exhibit a narrow symmetrical signal, [7] and Al EF species created upon steaming show an octahedral Al signal or are NMR-invisible. [8] Thus, a terminal (SiO) 3 AlOH group, an analogue of silanol groups well-known in zeolites, [9] could explain the nature of the "perturbed" Al FR atoms.…”

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confidence: 99%

Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by ²⁷Al{¹H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics

et al. 2014

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Zeolites are highly important heterogeneous catalysts. Besides Brønsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors--"perturbed" AlFR atoms in hydrated zeolites--were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3AlOH groups and are characterized by a broad (27)Al NMR resonance (δi = 59-62 ppm, CQ = 5 MHz, and η = 0.3-0.4) with a shoulder at 40 ppm in the (27)Al MAS NMR spectrum. Dehydroxylation of (SiO)3AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3Al Lewis sites exhibit an extremely broad (27)Al NMR resonance (δi ≈ 67 ppm, CQ ≈ 20 MHz, and η ≈ 0.1).

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“…[26] While, the weaker Lewis acidity and more severe diffusion limitation on the ZSM-5 catalyst went against the transition etherification reaction. [27] Compared with the microporous zeolites, all of the hierarchical HSZ catalysts showed 100 % BHMF conversion and much higher BEMF selectivity. Because the acidity of the HSZ catalysts was much weaker than that of the two microporous ones, the only reason for the better performance of the HSZ catalysts might be that the mesoporous structure could facilitate the etherification reaction of BHMF and ethanol.…”

Section: Resultsmentioning

confidence: 97%

“…For the ROP products, more Brønsted acid sites on the ZSM‐5 catalyst would favor the reaction of ring‐opening . While, the weaker Lewis acidity and more severe diffusion limitation on the ZSM‐5 catalyst went against the transition etherification reaction …”

Section: Resultsmentioning

confidence: 99%

Efficient Production of Furanic Diether in a Continuous Fixed Bed Reactor

Jin³

et al. 2019

ChemCatChem

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The selective conversion of 2,5‐bis(hydroxymethyl)furan (BHMF) to 2,5‐bis(ethoxymethyl)furan (BEMF) was investigated in a fixed bed reactor over several heterogeneous solid acid catalysts, including Amberlyst‐15, ZSM‐5, Mordenite, and a series of hierarchically structured ZSM‐5 zeolites (HSZ). The HSZ catalysts exhibited superior catalytic performance to other three commercial catalysts. The highest yield of BEMF (90.46 %) was obtained over the HSZ‐150 catalyst under the reaction condition of 140 °C, 2.0 MPa of H2, and 0.3 h−1 of WHSV. Moreover, the HSZ‐150 catalyst displayed an extremely good stability in the etherification reaction, maintaining more than 80 % yield of BEMF for about 80 h. The outstanding catalytic performance of the HSZ‐150 catalyst could be ascribed to that the presence of mesopores enhanced the etherification activity by alleviating the diffusion limitation, and the appropriate acidity improved the BEMF selectivity via suppressing the side reactions.

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Enhancement of Activity and Selectivity in Acid‐Catalyzed Reactions by Dealuminated Hierarchical Zeolites

Cited by 60 publications

References 19 publications

Tailoring and visualizing the pore architecture of hierarchical zeolites

Tailoring and visualizing the pore architecture of hierarchical zeolites

Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by ²⁷Al{¹H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics

Efficient Production of Furanic Diether in a Continuous Fixed Bed Reactor

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Enhancement of Activity and Selectivity in Acid‐Catalyzed Reactions by Dealuminated Hierarchical Zeolites

Cited by 60 publications

References 19 publications

Tailoring and visualizing the pore architecture of hierarchical zeolites

Tailoring and visualizing the pore architecture of hierarchical zeolites

Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by 27Al{1H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics

Efficient Production of Furanic Diether in a Continuous Fixed Bed Reactor

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Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by ²⁷Al{¹H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics