Operando Spectroscopy of the Gas-Phase Aldol Condensation of Propanal over Solid Base Catalysts

Hernández-Giménez, Ana M.; Ruiz‐Martínez, Javier; Puértolas, Begoña; Pérez‐Ramírez, Javier; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.

doi:10.1007/s11244-017-0836-7

Cited by 31 publications

(34 citation statements)

References 57 publications

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“…Mini review Hinshelwood type reaction, although Eley-Rideal mechanisms were proposed for the condensation of other short-chain aldehydes. 132,133 While the formation of crotonaldehyde via the aldol condensation of acetaldehyde is generally accepted as a keystep of the Toussaint-Kagan pathway from ethanol to butadiene, our understanding of the molecular-level phenomena taking place remains limited. Several mechanisms have been proposed, but the direct observation of surface intermediates and their correlation to activity has been limited, ostensibly due to their high instability.…”

Section: Catalysis Science and Technologymentioning

confidence: 99%

Ethanol-to-butadiene: the reaction and its catalysts

Pomalaza

Ponton

Capron

et al. 2020

Catal. Sci. Technol.

115

107

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Section: Catalysis Science and Technologymentioning

confidence: 99%

Ethanol-to-butadiene: the reaction and its catalysts

Pomalaza

Ponton

Capron

et al. 2020

Catal. Sci. Technol.

115

107

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“…Mechanistic studies of aldehyde dimerization over HAP at 533-673 K by Young et al and Hernández-Giménez et al have suggested that product desorption is slow in the absence of a hydrogen donor [57,58]. If product desorption is rate-limiting, then every surface reaction prior to that step is quasi-equilibrated, including the dehydration of DAA.…”

Section: Acetone Condensation Over Ie-hapmentioning

confidence: 99%

The mechanism and kinetics of methyl isobutyl ketone synthesis from acetone over ion-exchanged hydroxyapatite

Zheng

Shylesh

et al. 2018

Journal of Catalysis

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The synthesis of methyl isobutyl ketone (MIBK) can be carried out by the condensation of acetone in the presence of hydrogen over a supported metal catalyst. Previous studies have shown that hydroxyapatite is an excellent catalyst for condensation reactions. The present investigation was undertaken in order to elucidate the reaction mechanism and site requirements for acetone coupling to MIBK over a physical mixture of hydroxyapatite and Pd/SiO 2. The reaction is found to proceed by consecutive aldol addition to form diacetone alcohol (DAA), dehydration of DAA to mesityl oxide (MO), and hydrogenation of MO to MIBK. The products formed by feeding DAA and MO reveal that aldol addition of acetone is rapid and reversible, and that the subsequent dehydration of DAA is rate-limiting. Pyridine and CO 2 titration show that aldol dehydration occurs over basic sites via an E 1cB mechanism. A series of cationsubstituted hydroxyapatite samples were prepared by ion-exchange to further investigate the role of acid-base strength on catalyst performance. Characterization of these samples by PXRD, BET, ICP-OES, XPS, CO 2-TPD, and Raman spectroscopy demonstrated that the exchange procedure used does not affect the bulk properties of hydroxyapatite. DFT calculations reveal that in addition to affecting the Lewis acidity/basicity of the support, the size of the cation plays a significant role in the chemistry: cations that are too large (Ba 2+) or too small (Mg 2+) adversely affect reaction rates due to excessive stabilization of intermediate species. Strontium-exchanged hydroxyapatite was found to be the most active catalyst because it promoted a-hydrogen abstraction and CAO bond cleavage of DAA efficiently.

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“…Increasing temperature, only gas-phase species were observed, detected in the cooled-down spectra. Thus, IR bands at 1722 and 1700 cm -1 appeared at 160°C and 240°C, corresponding to PAL [34 ] and acetone [35 ] respectively. These species derived from the acid catalyzed 1,2-PD dehydration path, being easily desorbed to the gas phase.…”

Section: Ftir Spectra Of Adsorbed 12-pdmentioning

confidence: 97%

A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts

Bandinelli

Lambiase

Tabanelli

et al. 2019

Applied Catalysis A: General

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The gas-phase oxidehydration (ODH) of 1,2-propanediol to propionic acid has been studied as an intermediate step in the multi-step transformation of biosourced glycerol into methylmethacrylate. The reaction involves the dehydration of 1,2-propanediol into propionaldehyde, which occurs in the presence of acid active sites, and a second step of oxidation of the aldehyde to the carboxylic acid. The two reactions were carried out using a cascade strategy and multifunctional catalysts, made of W-Nb-O, W-V-O and W-Mo-V-O hexagonal tungsten bronzes, the same systems which are also active and selective in the ODH of glycerol into acrylic acid. Despite the similarities of reactions involved, the ODH of 1,2-propanediol turned out to be less selective than glycerol ODH, with best yield to propanoic acid no higher than 13%, mainly because of the parallel reaction of oxidative cleavage, occurring on the reactant itself, which led to the formation of C 1-C 2 compounds.

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Operando Spectroscopy of the Gas-Phase Aldol Condensation of Propanal over Solid Base Catalysts

Cited by 31 publications

References 57 publications

Ethanol-to-butadiene: the reaction and its catalysts

Ethanol-to-butadiene: the reaction and its catalysts

The mechanism and kinetics of methyl isobutyl ketone synthesis from acetone over ion-exchanged hydroxyapatite

A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts

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