Macrocellular Titanosilicate Monoliths as Highly Efficient Structured Olefin Epoxidation Catalysts

Self-standing macrocellular titanosilicate monolith foams are obtained using a one-pot sol-gel route and show excellent performance in the epoxidation of cyclohexene. Thanks to the High Internal Phase Emulsion (HIPE) templating method, the materials feature a high void fraction, a hierarchically porous texture and good mechanical strength. Highly dispersed Ti species can be incorporated in tetrahedral coordination the silica matrix. These characteristics allow the obtained ‘SiTi(HIPE)’ materials to reach high catalytic turnover in the epoxidation of cyclohexene. The monoliths can advantageously be used to run the reaction in continuous flow mode.

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Non-Hydrolytic Sol-Gel Route to a Family of Hybrid Mesoporous Aluminosilicate Ethanol Dehydration Catalysts

10.26434/chemrxiv.13377212 ◽

2020 ◽

Author(s):

Ales Styskalik ◽

Imène Kordoghli ◽

Claude Poleunis ◽

Arnaud Delcorte ◽

Denis Dochain ◽

...

Keyword(s):

Gas Phase ◽

Sol Gel ◽

Catalytic Performance ◽

Silica Matrix ◽

Ethanol Dehydration ◽

One Pot ◽

Water Contact ◽

Hybrid Silica ◽

Mesoporous Aluminosilicate ◽

Improved Performance

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 non-hydrolytic 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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Ethanol Dehydration over Hybrid Mesoporous Aluminosilicate Catalysts Obtained in One Pot by Non-Hydrolytic Sol-Gel

10.26434/chemrxiv.12354770 ◽

2020 ◽

Author(s):

Ales Styskalik ◽

Imène Kordoghli ◽

Claude Poleunis ◽

Arnaud Delcorte ◽

Zdenek Moravec ◽

...

Keyword(s):

Catalyst Activity ◽

Sol Gel ◽

Acid Sites ◽

Silica Matrix ◽

Methyl Groups ◽

Ethanol Dehydration ◽

Alcohol Dehydration ◽

One Pot ◽

Surface Hydrophilicity ◽

Silica Alumina

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 activity and stability. However, surface hydrophilicity or hydrophobicity can be suggested as another decisive catalyst property that can directly influence performance. For example, a more hydrophobic surface might be beneficial in repelling the co-product of the reaction, water. However, these aspects have been studied only scarcely in the context of alcohol dehydration. Here, a series of mesoporous hybrid aluminosilicate catalysts containing CH3Si groups was prepared in one pot by non-hydrolytic sol-gel (NHSG). The presence of the methyl groups was verified by IR, solid-state NMR, and ToF-SIMS. Aluminum is mostly incorporated in tetrahedral coordination in the hybrid silica matrix. Two parameters were varied: (i) the Si:Al ratio and (ii) the Si:MeSi ratio. On the one hand, changing the Si:Al ratio had a marked impact on hydrophilicity, as attested by water sorption measurements. On the other hand, unexpectedly, the introduction of methyl groups had no clear influence on sample hydrophilicity. Nevertheless, some of the methylated aluminosilicate catalysts markedly outperformed the purely inorganic catalysts and a commercial silica-alumina benchmark. While a direct influence of surface hydrophilicity or hydrophobicity could be excluded, characterization of acidity (IR-pyridine) revealed that these improved performances are correlated with a modification of the acidic properties in the hybrid catalysts caused by the presence of methyl groups. A decisive role of acidity in ethanol dehydration was confirmed by an experiment with delayed addition of the Al precursor in the NHSG synthesis. This led to a higher Al surface concentration, marked acid sites number increase, and better catalytic performance, even competing with HZSM-5 in terms of activity.

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Ethanol Dehydration over Hybrid Mesoporous Aluminosilicate Catalysts Obtained in One Pot by Non-Hydrolytic Sol-Gel

10.26434/chemrxiv.12354770.v1 ◽

2020 ◽

Author(s):

Ales Styskalik ◽

Imène Kordoghli ◽

Claude Poleunis ◽

Arnaud Delcorte ◽

Zdenek Moravec ◽

...

Keyword(s):

Catalyst Activity ◽

Sol Gel ◽

Acid Sites ◽

Silica Matrix ◽

Methyl Groups ◽

Ethanol Dehydration ◽

Alcohol Dehydration ◽

One Pot ◽

Surface Hydrophilicity ◽

Silica Alumina

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 activity and stability. However, surface hydrophilicity or hydrophobicity can be suggested as another decisive catalyst property that can directly influence performance. For example, a more hydrophobic surface might be beneficial in repelling the co-product of the reaction, water. However, these aspects have been studied only scarcely in the context of alcohol dehydration. Here, a series of mesoporous hybrid aluminosilicate catalysts containing CH3Si groups was prepared in one pot by non-hydrolytic sol-gel (NHSG). The presence of the methyl groups was verified by IR, solid-state NMR, and ToF-SIMS. Aluminum is mostly incorporated in tetrahedral coordination in the hybrid silica matrix. Two parameters were varied: (i) the Si:Al ratio and (ii) the Si:MeSi ratio. On the one hand, changing the Si:Al ratio had a marked impact on hydrophilicity, as attested by water sorption measurements. On the other hand, unexpectedly, the introduction of methyl groups had no clear influence on sample hydrophilicity. Nevertheless, some of the methylated aluminosilicate catalysts markedly outperformed the purely inorganic catalysts and a commercial silica-alumina benchmark. While a direct influence of surface hydrophilicity or hydrophobicity could be excluded, characterization of acidity (IR-pyridine) revealed that these improved performances are correlated with a modification of the acidic properties in the hybrid catalysts caused by the presence of methyl groups. A decisive role of acidity in ethanol dehydration was confirmed by an experiment with delayed addition of the Al precursor in the NHSG synthesis. This led to a higher Al surface concentration, marked acid sites number increase, and better catalytic performance, even competing with HZSM-5 in terms of activity.

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Effect of Ultrasonic Irradiation on Preparation and Properties of Ionogels

Journal of Nanomaterials ◽

10.1155/2012/570719 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 14

Author(s):

Yogendra Lal Verma ◽

Manish Pratap Singh ◽

Rajendra Kumar Singh

Keyword(s):

Ultrasonic Irradiation ◽

Sol Gel ◽

Porous Silica ◽

Porous Matrix ◽

Silica Matrix ◽

Tetraethyl Orthosilicate ◽

Aliphatic Chain ◽

One Pot ◽

Bet Analysis ◽

Vibrational Bands

Silica-gel matrices containing ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate viz. ionogels have been synthesized using one-pot nonhydrolytic sol-gel method and taking tetraethyl orthosilicate (TEOS) as starting precursor. Effect of ultrasonic irradiation on pore parameters of ionogels and vibrational properties of the IL upon confinement in the porous matrix has been investigated. The synthesized gels have been characterized by BET, DSC, TGA, and FTIR. BET analysis shows some changes in the pore parameters due to ultrasonic irradiation. DSC results indicate shift in glass transition temperature upon confinement of the IL. The FTIR spectra show changes in vibrational bands on confinement, particularly, the bands related to the imidazolium ring; aliphatic chain and anionPF6 −of the IL are found to shift upon confinement in porous silica matrix obtained due to ultrasonic irradiation. Ultrasonic irradiation has been found to affect the gelation dynamics and kinetics and pore parameters.

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Non-Hydrolytic Sol-Gel Route to a Family of Hybrid Mesoporous Aluminosilicate Ethanol Dehydration Catalysts

10.26434/chemrxiv.13377212.v1 ◽

2020 ◽

Author(s):

Ales Styskalik ◽

Imène Kordoghli ◽

Claude Poleunis ◽

Arnaud Delcorte ◽

Denis Dochain ◽

...

Keyword(s):

Gas Phase ◽

Sol Gel ◽

Catalytic Performance ◽

Silica Matrix ◽

Ethanol Dehydration ◽

One Pot ◽

Water Contact ◽

Hybrid Silica ◽

Mesoporous Aluminosilicate ◽

Improved Performance

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 non-hydrolytic 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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Synthesis, Structural, Morphological and Thermal Characterization of Five Different Silica-Polyethylene Glycol-Chlorogenic Acid Hybrid Materials

Polymers ◽

10.3390/polym13101586 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1586

Author(s):

Michelina Catauro ◽

Pavel Šiler ◽

Jiří Másilko ◽

Roberta Risoluti ◽

Stefano Vecchio Ciprioti

Keyword(s):

Polyethylene Glycol ◽

Chlorogenic Acid ◽

Hybrid Materials ◽

Sol Gel ◽

Antibacterial Properties ◽

Silica Matrix ◽

Sem Images ◽

Fixed Amount ◽

Organic Components ◽

Free Material

The present study investigated the structure, morphology, thermal behavior, and bacterial growth analysis of novel three-component hybrid materials synthesized by the sol-gel method. The inorganic silica matrix was weakly bonded to the network of two organic components: a well-known polymer such as polyethylene glycol (PEG, average molar mass of about 4000 g/mol), and an antioxidant constituted by chlorogenic acid (CGA). In particular, a first series was made by a 50 wt% PEG-based (CGA-free) silica hybrid along with two 50 wt% PEG-based hybrids containing 10 and 20 wt% of CGA (denoted as SP50, SP50C10 and SP50C20, respectively). A second series contained a fixed amount of CGA (20 wt%) in silica-based hybrids: one was the PEG-free material (SC20) and the other two contained 12 and 50 wt% of PEG, respectively (SP12C20 and SP50C20, respectively), being the latter already included in the first series. The X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images of freshly prepared materials confirmed that all the materials were amorphous and homogeneous regardless of the content of PEG or CGA. The thermogravimetric (TG) analysis revealed a higher water content was adsorbed into the two component hybrids (SP50 and SC20) because of the availability of a larger number of H-bonds to be formed with water with respect to those of silica/PEG/CGA (SPC), where silica matrix was involved in these bonds with both organic components. Conversely, the PEG-rich materials (SP50C10 and SP50C20, both with 50 wt% of the polymer) retained a lower content of water. Decomposition of PEG and CGA occurred in almost the same temperature interval regardless of the content of each organic component. The antibacterial properties of the SiO2/PEG/CGA hybrid materials were studied in pellets using either Escherichia coli and Enterococcus faecalis, respectively. Excellent antibacterial activity was found against both bacteria regardless of the amount of polymer in the hybrids.

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Luminescence properties of the rare earth (Eu3+ and Tb3+) complexes with 1,10-Phenanthroline incorporated in silica matrix by a sol–gel method

Materials Science and Engineering B ◽

10.1016/s0921-5107(97)00216-x ◽

1998 ◽

Vol 52 (2-3) ◽

pp. 123-128 ◽

Cited By ~ 39

Author(s):

B Yan ◽

H.J Zhang ◽

J.Z Ni

Keyword(s):

Rare Earth ◽

Sol Gel ◽

Silica Matrix ◽

Luminescence Properties ◽

Gel Method ◽

Sol Gel Method ◽

The Rare Earth

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Bioencapsulation in Sol-Gel Glasses

MRS Proceedings ◽

10.1557/proc-519-171 ◽

1998 ◽

Vol 519 ◽

Cited By ~ 9

Author(s):

L. Bergogne ◽

S. Fennouh ◽

J. Livage ◽

C. Roux

Keyword(s):

Sol Gel ◽

Porous Silica ◽

Silica Matrix ◽

Whole Cells ◽

The Past ◽

Wide Range ◽

Activity Of Enzymes ◽

Gel Glasses ◽

Micro Organisms

AbstractBioencapsulation in sol-gel materials has been widely studied during the past decade. Trapped species appear to retain their bioactivity in the porous silica matrix. Small analytes can diffuse through the pores allowing bioreactions to be performed in-situ, inside the sol-gel glass. A wide range of biomolecules and micro-organisms have been encapsulated. The catalytic activity of enzymes is used for the realization of biosensors or bioreactors. Antibody-antigen recognition has been shown to be feasible within sol-gel matrices. Trapped antibodies bind specifically the corresponding haptens and can be used for the detection of traces of chemicals. Even whole cells are now encapsulated without any alteration of their cellular organization. They can be used for the production of chemicals or as antigens for immunoassays.

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