Hybrid mesoporous aluminosilicate catalysts obtained by non-hydrolytic sol–gel for ethanol dehydration

Stýskalík, Aleš; Kordoghli, Imene; Poleunis, Claude; Delcorte, Arnaud; Moravec, Zdeněk; Šimoníková, Lucie; Kanický, Viktor; Aprile, Carmela; Fusaro, Luca; Debecker, Damien P.

doi:10.1039/d0ta07016e

Cited by 17 publications

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References 74 publications

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“…These molar ratios were chosen according to our previous study on methylated aluminosilicates and kept for all samples prepared in this study. 12 The autoclave with the reaction mixture was sealed and kept in an oven at 110 °C for 72 hrs for gelation (Eqn. 1).…”

Section: Methodsmentioning

confidence: 99%

“…Sample p_Me has already been presented in our previous paper, where it was labeled "15Si-1MeSi-1Al"). 12 A purely inorganic benchmark catalyst with the same Si:Al nominal ratio was prepared in the same way using only SiCl4 as a silicon precursor (16Si-1Al). Precise reactant masses used in the syntheses can be found in Table 1.…”

Section: Methodsmentioning

confidence: 99%

“…8,[34][35][36][37] In the specific case of gas-phase ethanol dehydration to ethylene, we have shown two important factors influencing strongly the behavior of methylated metallosilicates: (i) the hydrothermal stability of Si-C bonds (which is unsatisfactory if aromatic organic groups are directly bound to Si atoms) 27 and (ii) the number, nature, and strength of acid sites. 12,38 On the other hand, studying a series of methylated aluminosilicate materials, a direct influence of hydrophobicity on the catalytic performance was not demonstrated. 12 Herein we report on a series of hybrid aluminosilicates prepared by NHSG, in which the organic groups attached to the inorganic matrices were varied: bridging and terminal, aliphatic and aromatic groups were incorporated.…”

Section: Introductionmentioning

confidence: 99%

“…12,38 On the other hand, studying a series of methylated aluminosilicate materials, a direct influence of hydrophobicity on the catalytic performance was not demonstrated. 12 Herein we report on a series of hybrid aluminosilicates prepared by NHSG, in which the organic groups attached to the inorganic matrices were varied: bridging and terminal, aliphatic and aromatic groups were incorporated. The catalysts' structure, porosity, acidity, and hydrophobicity were followed by a number of analytical methods and correlated with performance in ethanol dehydration.…”

Section: Introductionmentioning

confidence: 99%

“…longer aliphatic chains, aromatic rings, fluorinated organic groups) has been reported much less often. Such a broadening of applied materials however might bring other positive effects: not only hydrophobicity alteration (that may or may not be observed upon methyl groups introduction), 3,[11][12][13] including also selective adsorption of reactants induced by specific non-bonding interactions (e.g. π-π stacking), 14 but also porosity changes, 15,16 hydrothermal stability improvement, 17 or modulation of catalyst sites strength and accessibility.…”

Section: Introductionmentioning

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: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

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Titanosilicate Epoxidation Catalysts: A Review of Challenges and Opportunities

2021

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Epoxidation reactions are tremendously important for modern chemistry, as they lead to series of highly useful bulk and fine chemicals, monomers, and intermediates for organic synthesis. Progress in epoxidation processes goes hand in hand with the advancement made in catalysis science. In this context, heterogeneous catalysts, and particularly Ti‐based formulations, are playing a central role and have seen tremendous developments over the past two decades, leveraging on advanced materials science. The aim of this review is to illustrate the various strategies of titanosilicate catalysts preparation that can lead to more versatile, more performant, and greener epoxidation processes. We successively cover (i) supported catalysts, obtained by the grafting of Ti species onto preformed silica supports, (ii) microporous crystalline titanosilicates (zeolites), and (iii) amorphous titanosilicates obtained by sol‐gel chemistry. For each category, with an emphasis on catalyst preparation, the challenges that have to be tackled to boost catalyst performance are highlighted. From that point, we present a critical review of the different approaches that have been proposed in the primary literature to tailor the properties that govern catalysts performance (activity, selectivity, stability, ease of handling). This is done by better controlling the nature of the active surface species, adapting particles size and shape, optimizing texture, modifying surface chemistry, etc. These lines of attack encompass molecular approaches for the grafting of well‐defined species, top‐down and bottom‐up synthesis of hierarchically porous zeolites, advanced sol‐gel routes potentially performed in non‐conventional media or coupled with original processing, preparation of self‐standing monoliths, etc. Future research directions are discussed with emphasis on the application scope of new catalytic materials and possible approaches to increase catalyst performance.

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Hydrophobicity Boosts Catalytic Activity: The Tailoring of Aluminosilicates with Trimethylsilyl Groups**

et al. 2023

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Introducing organic groups into metal silicate catalysts and thus supposedly changing the surface hydrophobicity has been shown to enhance the catalyst performance in various reactions. However, the organic groups introduction does not unambiguously guarantee hydrophobicity control. Therefore, a thorough characterization is necessary to provide a complete view of the interaction between the catalyst surface, reactants, and products. Herein, an aluminosilicate catalyst with welldispersed Al atoms was prepared via the non-hydrolytic sol-gel method. This material was post-synthetically modified with trimethylsilyl groups; their number on the catalyst surface was controlled via a temperature-vacuum pretreatment. In such a way, aluminosilicate materials with similar porosity, structure, and acid site strength and quality were obtained. Notably, the water sorption measurements showed that trimethylsilylated aluminosilicates adsorb 2.5-3 times less water than the parent material (p/p 0 = 0.3). The turn-over-frequency in epoxide ring opening and ethanol dehydration scaled up with the number of trimethylsilyl groups grafted on the catalyst surface. Particularly, the heavily trimethylsilylated sample achieved three to five times higher turnover-frequency in styrene oxide aminolysis than the parent aluminosilicate material. To the best of the authors' knowledge, it exhibited the most active Al sites for epoxide aminolysis in the present literature.

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Hybrid mesoporous aluminosilicate catalysts obtained by non-hydrolytic sol–gel for ethanol dehydration

Abstract: Ethanol dehydration is effectively catalyzed by solid acids, such as HZSM-5, alumina, or silica-alumina. In these catalysts, the amount, nature, and strength of acid sites is believed to determine catalyst...

Cited by 17 publications

References 74 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

Titanosilicate Epoxidation Catalysts: A Review of Challenges and Opportunities

Hydrophobicity Boosts Catalytic Activity: The Tailoring of Aluminosilicates with Trimethylsilyl Groups**

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