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

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

<p>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 CH<sub>3</sub>Si 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.</p>

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

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

<p>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 CH<sub>3</sub>Si 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.</p>

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

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.<br>

Mildly Acidic Aluminosilicate Catalysts for Stable Performance in Ethanol Dehydration

2020 ◽  
Author(s):  
Ales Styskalik ◽  
Vit Vykoukal ◽  
Luca Fusaro ◽  
Carmela Aprile ◽  
Damien Debecker
Keyword(s):  
Sol Gel ◽  
Coke Formation ◽  
Strong Acid ◽  
Acid Sites ◽  
High Specific Surface Area ◽  
Ethylene Oligomerization ◽  
Zeolite Catalysts ◽  
Activity Levels ◽  
Ethanol Dehydration ◽  
Silica Alumina

Ethanol dehydration is effectively catalyzed by strongly acidic zeolite catalysts which are known, however, to exhibit poor time on stream stability. Alumina and silica-alumina on the other hand are relatively stable but reach only low activity levels. Here, a series of aluminosilicate catalysts (Si:Al ratio = 16) was prepared by non-hydrolytic sol-gel (NHSG) and are shown to feature an intermediate level of activity, between the HZSM-5 zeolite and a commercial silica-alumina. Importantly, the best samples, were very stable with time on stream. Unlike HZSM-5, which also catalyzes ethylene oligomerization due to its strong acid sites and is therefore prone to coking, NHSG prepared catalysts did not produce any traces of ethylene oligomers and did not show any trace of coke formation. Characterization (ICP-OES, N<sub>2</sub> physisorption, TEM, XPS, IR coupled with pyridine adsorption, Raman spectroscopy, solid state NMR spectroscopy) reveal that the unconventional synthetic method presented here allowed to prepare mesoporous aluminosilicate materials with a remarkable degree of homogeneity. It is this thorough dispersion of Al in the amorphous silicate matrix which is responsible for the formation of acid sites which are intermediate (in terms of strength and nature) between those of commercial silica-alumina and HZSM-5 zeolite. The texture of the best NHSG catalyst – mainly mesoporous with a high specific surface area (800 m² g<sup>−1</sup>) and pore volume (0.5 cm³ g<sup>−1</sup>) – was also unaffected after reaction. To overcome deactivation issues in ethanol dehydration, this study suggests to target amorphous aluminosilicate catalysts with open mesoporosity and with an intimate mixing of Al and Si.

Mildly Acidic Aluminosilicate Catalysts for Stable Performance in Ethanol Dehydration

2020 ◽  
Author(s):  
Ales Styskalik ◽  
Vit Vykoukal ◽  
Luca Fusaro ◽  
Carmela Aprile ◽  
Damien Debecker
Keyword(s):  
Sol Gel ◽  
Coke Formation ◽  
Strong Acid ◽  
Acid Sites ◽  
High Specific Surface Area ◽  
Ethylene Oligomerization ◽  
Zeolite Catalysts ◽  
Activity Levels ◽  
Ethanol Dehydration ◽  
Silica Alumina

Ethanol dehydration is effectively catalyzed by strongly acidic zeolite catalysts which are known, however, to exhibit poor time on stream stability. Alumina and silica-alumina on the other hand are relatively stable but reach only low activity levels. Here, a series of aluminosilicate catalysts (Si:Al ratio = 16) was prepared by non-hydrolytic sol-gel (NHSG) and are shown to feature an intermediate level of activity, between the HZSM-5 zeolite and a commercial silica-alumina. Importantly, the best samples, were very stable with time on stream. Unlike HZSM-5, which also catalyzes ethylene oligomerization due to its strong acid sites and is therefore prone to coking, NHSG prepared catalysts did not produce any traces of ethylene oligomers and did not show any trace of coke formation. Characterization (ICP-OES, N<sub>2</sub> physisorption, TEM, XPS, IR coupled with pyridine adsorption, Raman spectroscopy, solid state NMR spectroscopy) reveal that the unconventional synthetic method presented here allowed to prepare mesoporous aluminosilicate materials with a remarkable degree of homogeneity. It is this thorough dispersion of Al in the amorphous silicate matrix which is responsible for the formation of acid sites which are intermediate (in terms of strength and nature) between those of commercial silica-alumina and HZSM-5 zeolite. The texture of the best NHSG catalyst – mainly mesoporous with a high specific surface area (800 m² g<sup>−1</sup>) and pore volume (0.5 cm³ g<sup>−1</sup>) – was also unaffected after reaction. To overcome deactivation issues in ethanol dehydration, this study suggests to target amorphous aluminosilicate catalysts with open mesoporosity and with an intimate mixing of Al and Si.

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

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.<br>

Macrocellular Titanosilicate Monoliths as Highly Efficient Structured Olefin Epoxidation Catalysts

2019 ◽  
Author(s):  
Valentin Smeets ◽  
Ludivine van den Biggelaar ◽  
Tarek Barakat ◽  
Eric M. Gaigneaux ◽  
Damien Debecker
Keyword(s):  
Sol Gel ◽  
Silica Matrix ◽  
Flow Mode ◽  
Tetrahedral Coordination ◽  
Excellent Performance ◽  
One Pot ◽  
Templating Method ◽  
Porous Texture ◽  
Internal Phase ◽  
Epoxidation Of Cyclohexene

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.<br>

scholarly journals Catalytic myrtenol amination over gold, supported on alumina doped with ceria and zirconia

2018 ◽  
Vol 5 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Yu.S. Demidova ◽  
I.L. Simakova ◽  
E.V. Suslov ◽  
K.P. Volcho ◽  
N.F. Salakhutdinov ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Sol Gel ◽  
Gold Catalyst ◽  
Catalyst Support ◽  
Acid Sites ◽  
One Pot ◽  
Gel Method ◽  
Sol Gel Method ◽  
Alcohol Activation ◽  
The One

Abstract In the current work gold catalysts supported on both commercial oxides and oxides synthesized by the sol-gel method were used for the one-pot alcohol amination of myrtenol. In general, utilization of metal oxides synthesized by the sol-gel method as the gold catalyst support enhanced the knowledge regarding key parameters determining catalytic behavior. Synthesized alumina was characterized by stronger acid sites favoring primary amine accumulation on the catalyst surface, as compared to the commercial oxide. Utilization of mixed metal oxides synthesized by the sol-gel method resulted in the non-additive behavior of different oxides enhancing the catalytic activity. Introduction of ceria into alumina modified the support basicity resulting in more efficient alcohol activation.

scholarly journals Preparation of Mesoporous Mn–Ce–Ti–O Aerogels by a One-Pot Sol–Gel Method for Selective Catalytic Reduction of NO with NH3

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 475
Author(s):  
Yabin Wei ◽  
Shuangling Jin ◽  
Rui Zhang ◽  
Weifeng Li ◽  
Jiangcan Wang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Lewis Acid ◽  
Catalytic Reduction ◽  
Sol Gel ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
One Pot ◽  
Gel Method ◽  
Nh3 Scr ◽  
Composite Aerogels

Novel Mn–Ce–Ti–O composite aerogels with large mesopore size were prepared via a one-pot sol–gel method by using propylene oxide as a network gel inducer and ethyl acetoacetate as a complexing agent. The effect of calcination temperature (400, 500, 600, and 700 °C) on the NH3–selective catalytic reduction (SCR) performance of the obtained Mn–Ce–Ti–O composite aerogels was investigated. The results show that the Mn–Ce–Ti–O catalyst calcined at 600 °C exhibits the highest NH3–SCR activity and lowest apparent activation energy due to its most abundant Lewis acid sites and best reducibility. The NO conversion of the MCTO-600 catalyst maintains 100% at 200 °C in the presence of 100 ppm SO2, showing the superior resistance to SO2 poisoning as compared with the MnOx–CeO2–TiO2 catalysts reported the literature. This should be mainly attributed to its large mesopore sizes with an average pore size of 32 nm and abundant Lewis acid sites. The former fact facilitates the decomposition of NH4HSO4, and the latter fact reduces vapor pressure of NH3. The NH3–SCR process on the MCTO-600 catalyst follows both the Eley–Rideal (E–R) mechanism and the Langmuir–Hinshelwood (L–H) mechanism.

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

2020 ◽  
Vol 8 (44) ◽  
pp. 23526-23542
Author(s):  
Ales Styskalik ◽  
Imene Kordoghli ◽  
Claude Poleunis ◽  
Arnaud Delcorte ◽  
Zdenek Moravec ◽  
...  
Keyword(s):  
Sol Gel ◽  
Methyl Groups ◽  
Ethanol Dehydration ◽  
Mesoporous Aluminosilicate ◽  
Highly Porous

Introduction of methyl groups into the highly porous aluminosilicates prepared by non-hydrolytic sol–gel improves the ethylene yields in ethanol dehydration.

scholarly journals Ethanol Dehydration over WO3/TiO2Catalysts Using Titania Derived from Sol-Gel and Solvothermal Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Anchale Tresatayawed ◽  
Peangpit Glinrun ◽  
Bunjerd Jongsomjit
Keyword(s):  
Physicochemical Properties ◽  
Pore Volume ◽  
Catalytic Properties ◽  
Sol Gel ◽  
Acid Sites ◽  
Ethanol Conversion ◽  
Ethanol Dehydration ◽  
Preparation Methods ◽  
Solvothermal Methods ◽  
Different Characteristics

The present study aims to investigate the catalytic ethanol dehydration to higher value products including ethylene, diethyl ether (DEE), and acetaldehyde. The catalysts used for this reaction were WO3/TiO2catalysts having W loading of 13.5 wt.%. For a comparative study, the TiO2supports employed were varied by two different preparation methods including the sol-gel and solvothermal-derived TiO2supports, denoted as TiO2-SG and TiO2-SV, respectively. It is obvious that the different preparation methods essentially altered the physicochemical properties of TiO2supports. It was found that the TiO2-SV exhibited higher surface area and pore volume and larger amounts of acid sites than those of TiO2-SG. As a consequence, different characteristics of support apparently affected the catalytic properties of WO3/TiO2catalysts. As expected, both catalysts WO3/TiO2-SG and WO3/TiO2-SV exhibited increased ethanol conversion with increasing temperatures from 200 to 400°C. It appeared that the highest ethanol conversion (ca. 88%) at 400°C was achieved by the WO3/TiO2-SV catalysts due to its high acidity. It is worth noting that the presence of WO3onto TiO2-SV yielded a remarkable increase in DEE selectivity (ca. 68%) at 250°C. In summary, WO3/TiO2-SV catalyst is promising to convert ethanol into ethylene and DEE, having the highest ethylene yield of ca. 77% at 400°C and highest DEE yield of ca. 26% at 250°C. These can be attributed to proper pore structure, acidity, and distribution of WO3.

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