Acidity of Al–O(H)–Al Sites in Molecular Aluminosilicate Models Enables Alcohol Dehydration Reactions

2021 ◽  
Author(s):  
Fabian Beckmann ◽  
Kapil S. Lokare ◽  
Lukas Lätsch ◽  
Christophe Copéret ◽  
Christian Limberg
Keyword(s):  
Alcohol Dehydration ◽  
Dehydration Reactions

Alcohol Dehydration Reactions over Tungstated Zirconia Catalysts

1997 ◽  
Vol 169 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Gustavo Larsen ◽  
Edgar Lotero ◽  
Lucı́a M. Petkovic ◽  
David S. Shobe
Keyword(s):  
Tungstated Zirconia ◽  
Alcohol Dehydration ◽  
Dehydration Reactions

Silica-supported heteropolyacids as catalysts in alcohol dehydration reactions

2000 ◽  
Vol 161 (1-2) ◽  
pp. 223-232 ◽  
Author(s):  
P Vázquez ◽  
L Pizzio ◽  
C Cáceres ◽  
M Blanco ◽  
H Thomas ◽  
...  
Keyword(s):  
Alcohol Dehydration ◽  
Dehydration Reactions

Effects of Novel Supports on the Physical and Catalytic Properties of Tungstophosphoric Acid for Alcohol Dehydration Reactions

2008 ◽  
Vol 49 (3-4) ◽  
pp. 259-267 ◽  
Author(s):  
Jose E. Herrera ◽  
Ja Hun Kwak ◽  
Jian Zhi Hu ◽  
Yong Wang ◽  
Charles H. F. Peden
Keyword(s):  
Catalytic Properties ◽  
Tungstophosphoric Acid ◽  
Alcohol Dehydration ◽  
Dehydration Reactions

(100) facets of γ-Al2O3: The Active Surfaces for Alcohol Dehydration Reactions

2011 ◽  
Vol 141 (5) ◽  
pp. 649-655 ◽  
Author(s):  
Ja Hun Kwak ◽  
Donghai Mei ◽  
Charles H. F. Peden ◽  
Roger Rousseau ◽  
János Szanyi
Keyword(s):  
Alcohol Dehydration ◽  
Active Surfaces ◽  
Dehydration Reactions

scholarly journals Porous Silicates Modified with Zirconium Oxide and Sulfate Ions for Alcohol Dehydration Reactions

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Heriberto Esteban Benito ◽  
Ricardo García Alamilla ◽  
Juan Manuel Hernández Enríquez ◽  
Francisco Paraguay Delgado ◽  
Daniel Lardizabal Gutiérrez ◽  
...  
Keyword(s):  
Zirconium Oxide ◽  
Cetyltrimethylammonium Bromide ◽  
Pyridine Adsorption ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Alcohol Dehydration ◽  
Sulfate Ions ◽  
X Ray ◽  
Dehydration Reactions

Porous silicates were synthesized by a nonhydrothermal method, using sodium silicate as a source of silica and cetyltrimethylammonium bromide as a template agent. Catalysts were characterized using thermogravimetric analysis, N2physisorption, X-ray diffraction, FTIR spectroscopy, pyridine adsorption, potentiometric titration withn-butylamine, scanning electronic microscopy, and transmission electronic microscopy. The surface area of the materials synthesized was greater than 800 m2/g. The introduction of zirconium atoms within the porous silicates increased their acid strength from −42 to 115 mV, while the addition of sulfate ions raised this value to 470 mV. The catalytic activity for the dehydration of alcohols yields conversions of up to 70% for ethanol and 30% for methanol.

scholarly journals Highly Porous Hybrid Metallosilicate Materials Prepared by Non-Hydrolytic Sol-Gel: Hydrothermal Stability and Catalytic Properties in Ethanol Dehydration

2019 ◽  
Author(s):  
Ales Styskalik ◽  
Imene Kordoghli ◽  
Claude Poleunis ◽  
Arnaud Delcorte ◽  
Carmela Aprile ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Surface Acidity ◽  
Sol Gel ◽  
Silica Matrix ◽  
Alcohol Dehydration ◽  
Periodic Mesoporous Organosilica ◽  
Texture Surface ◽  
Hybrid Silica ◽  
Dehydration Reactions ◽  
Highly Porous

<div> <p>Herein, we present novel phenylene- and xylylene-bridged silica and metallosilicate materials prepared by non-hydrolytic sol-gel. The hybrid silica are highly porous, chemically similar to periodic mesoporous organosilica (PMO), but amorphous. Analogous hybrid metallosilicates are obtained by directly incorporating Al, Nb, or Sn in the hybrid silica framework. Exhibiting open texture, surface acidity and tunable hydrophobicity, these materials are excellent candidates for catalytic alcohol dehydration reactions. The gas-phase hydrothermal and thermal stability of these materials is examined. While the hybrid silica is expectedly stable, a stark decrease in stability is observed for phenylene bridged silsesquioxanes upon metal introduction. The extent of the hydrolytic Si−C(sp<sup>2</sup>) bond cleavage is quantitatively followed by <sup>29</sup>Si MAS NMR, TG analysis, and GC-FID analysis of effluent coming from samples exposed to water vapor. Two important features affecting the hydrothermal and thermal stability are identified: (i) the homogeneity of metal dispersion within the silica matrix, and (ii) the electronegativity of the incorporated metal. The stability of hybrid metallosilicates is significantly improved by replacing the phenylene bridges with xylylene bridges, due to the presence of more stable Si−C(sp<sup>3</sup>) bonds. Interestingly, the latter hybrid metallosilicate proves to be an active catalyst for the dehydration of ethanol to ethylene. Unlike the other hybrid materials presented here, it reaches high ethylene yields without undergoing degradation and deactivation.</p> </div>

scholarly journals Highly Porous Hybrid Metallosilicate Materials Prepared by Non-Hydrolytic Sol-Gel: Hydrothermal Stability and Catalytic Properties in Ethanol Dehydration

2019 ◽  
Author(s):  
Ales Styskalik ◽  
Imene Kordoghli ◽  
Claude Poleunis ◽  
Arnaud Delcorte ◽  
Carmela Aprile ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Surface Acidity ◽  
Sol Gel ◽  
Silica Matrix ◽  
Alcohol Dehydration ◽  
Periodic Mesoporous Organosilica ◽  
Texture Surface ◽  
Hybrid Silica ◽  
Dehydration Reactions ◽  
Highly Porous

<div> <p>Herein, we present novel phenylene- and xylylene-bridged silica and metallosilicate materials prepared by non-hydrolytic sol-gel. The hybrid silica are highly porous, chemically similar to periodic mesoporous organosilica (PMO), but amorphous. Analogous hybrid metallosilicates are obtained by directly incorporating Al, Nb, or Sn in the hybrid silica framework. Exhibiting open texture, surface acidity and tunable hydrophobicity, these materials are excellent candidates for catalytic alcohol dehydration reactions. The gas-phase hydrothermal and thermal stability of these materials is examined. While the hybrid silica is expectedly stable, a stark decrease in stability is observed for phenylene bridged silsesquioxanes upon metal introduction. The extent of the hydrolytic Si−C(sp<sup>2</sup>) bond cleavage is quantitatively followed by <sup>29</sup>Si MAS NMR, TG analysis, and GC-FID analysis of effluent coming from samples exposed to water vapor. Two important features affecting the hydrothermal and thermal stability are identified: (i) the homogeneity of metal dispersion within the silica matrix, and (ii) the electronegativity of the incorporated metal. The stability of hybrid metallosilicates is significantly improved by replacing the phenylene bridges with xylylene bridges, due to the presence of more stable Si−C(sp<sup>3</sup>) bonds. Interestingly, the latter hybrid metallosilicate proves to be an active catalyst for the dehydration of ethanol to ethylene. Unlike the other hybrid materials presented here, it reaches high ethylene yields without undergoing degradation and deactivation.</p> </div>

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

scholarly journals Pervasive fluid-rock interaction in subducted oceanic crust revealed by oxygen isotope zoning in garnet

2021 ◽  
Vol 176 (7) ◽  
Author(s):  
Thomas Bovay ◽  
Daniela Rubatto ◽  
Pierre Lanari
Keyword(s):  
Oxygen Isotope ◽  
Western Alps ◽  
Large Contribution ◽  
Chemical Mapping ◽  
Rock Interaction ◽  
Rock Density ◽  
Chemical Zoning ◽  
Dehydration Reactions ◽  
Subducted Oceanic Crust ◽  
Eclogite Facies

AbstractDehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

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