Isopropanol Dehydration on Amorphous Silica–Alumina: Synergy of Brønsted and Lewis Acidities at Pseudo‐Bridging Silanols

Larmier, Kim; Chizallet, Céline; Maury, S.; Cadran, Nicolas; Abboud, Johnny; Lamic‐Humblot, Anne‐Félicie; Marceau, Éric; Lauron‐Pernot, Hélène

doi:10.1002/anie.201609494

Cited by 51 publications

(142 citation statements)

References 49 publications

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“…To design active non‐acidic catalysts based on our previous observations, we thus decided to use a weakly acidic support, such as alumina, and a non‐innocent precursor that could reconstitute a silica‐alumina cluster in close vicinity to the metallic sites. This would force the proximity of nickel with a Brønsted acid site, either terminal or pseudo‐bridged one, and enhance electrodeficiency of the nickel atom to increase its activity . Inspired by the action of ammonium hexafluorosilicate, (NH 4 ) 2 SiF 6 , to dealuminate zeolites by substituting aluminum atoms with silicon atoms under the action of SiF 6 2− , we used commercial nickel hexafluorosilicate, NiSiF 6 , as a nickel precursor for incipient wetness impregnation on alumina.…”

Section: Resultsmentioning

confidence: 99%

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

2017

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Only a few catalytic transformations can be efficiently catalyzed by both homogeneous or heterogeneous technologies, with short olefin oligomerization promoted by a nickel‐based catalysts among them. Homogeneous and heterogeneous catalysis are often opposed in terms of activity, active‐site description or recyclability, traditionally mentioned as “homogeneous versus. heterogeneous”. Unlike previous studies, we propose to emphasize the similarities between both catalysis by comparing industrially representative results obtained in continuous flow‐mode under similar mild conditions. A detailed analysis of both primary products of olefins oligomerization, and a set of secondary products obtained in experimental assays completed with recently published results of DFT calculations prompted us to postulate a common mechanistic pathway for nickel‐catalyzed ethylene oligomerization. Heterogeneous metallic ethylene oligomerization, for which nickel active sites identification has indeed long been under debate, seems to follow the Cossee–Arlman mechanism, well accepted as major mechanism in the homogeneous counterpart. This analysis allowed us to design an unprecedented heterogeneous catalyst active for ethylene and butene oligomerization.

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Section: Resultsmentioning

confidence: 99%

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

2017

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“…LAS are able to abstract hydride or electron-rich groups (i. e. À OH) to form carbenium ions, and to drive the hydrocarbon reactions. [10][11] Therefore, characterizing the type and population density of surface acid sites, as well as their local structure is of great importance.…”

Section: Introductionmentioning

confidence: 99%

NMR Spectroscopic Characterization of Flame‐Made Amorphous Silica‐Alumina for Cyclohexanol and Glyceraldehyde Conversion

et al. 2019

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Amorphous silica‐aluminas (ASAs), possessing both Brønsted acid sites (BAS) and Lewis acid sites (LAS), are important bifunctional catalysts in various industrial applications. Solid‐state NMR spectroscopy has been widely used for characterizing the local structure and the surface sites of ASAs with probe molecules. In this work, four‐, five‐ and six‐coordinated Al species have been observed on the flame‐made ASAs by 27Al MQ MAS NMR experiment. 1H/27Al TRAPDOR MAS NMR experiments confirmed that surface Al species contribute to the formation of BAS and protonate ammonia probe molecules. The adsorption of ammonia on Lewis acidic Al sites (δ1H=3.0 ppm) was evidenced by various 1H MAS NMR experiments on samples dehydrated at different temperatures, allowing the distinction from ammonium ions (δ1H=6.7 ppm) formed at BAS. The signal of ammonia adsorbed on LAS increased with increasing Al content in the ASAs. These properties together with the absence of pore diffusional constraints render the flame‐made ASAs excellent catalysts for cyclohexanol dehydration and the conversion of glyceraldehyde in ethanol to ethyl lactate, outperforming the performance of other ASAs or zeolites.

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“…According to the reports, the shape and porosity of amorphous materials formed upon calcination depended on chemical composition and drying conditions. It is worth pondering that how to cause disorder in the crystalline solid state, so that the crystalline state can be transformed into amorphous state . In recent years, researchers have made continuous efforts to develop a variety of methods of synthesizing amorphous materials.…”

Section: Introductionmentioning

confidence: 99%

Recent Progress in Some Amorphous Materials for Supercapacitors

Zheng

et al. 2018

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A breakthrough in technologies having "green" and sustainable energy storage conversion is urgent, and supercapacitors play a crucial role in this area of research. Owing to their unique porous structure, amorphous materials are considered one of the best active materials for high-performance supercapacitors due to their high specific capacity, excellent cycling stability, and fast charging rate. This Review summarizes the synthesis of amorphous materials (transition metal oxides, carbon-based materials, transition metal sulfides, phosphates, hydroxides, and their complexes) to highlight their electrochemical performance in supercapacitors.

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Isopropanol Dehydration on Amorphous Silica–Alumina: Synergy of Brønsted and Lewis Acidities at Pseudo‐Bridging Silanols

Cited by 51 publications

References 49 publications

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

NMR Spectroscopic Characterization of Flame‐Made Amorphous Silica‐Alumina for Cyclohexanol and Glyceraldehyde Conversion

Recent Progress in Some Amorphous Materials for Supercapacitors

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