23-P-23 - Catalytic in-situ infrared spectroscopic study of n-butyraldehyde aldol condensation

Rymsa, Ute; Hunger, Marc; Weitkamp, Jens

doi:10.1016/s0167-2991(01)81488-9

Cited by 3 publications

(9 citation statements)

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“…[1,2] This route however has serious drawbacks: i) corrosion of the equipment, ii) formation of by-products such as sodium butanoate or higher molecular weight species resulted from deeper 2-EN condensation; iii) extensive production of organic and alkali contaminated wastes. [3,4] Therefore significant efforts are focused at the development of solid base catalysts for butanal condensation. The catalysts reported so far include MgO, SrO, [3,5] alkali-exchanged zeolites, [6] NiÀ Ce doped alumina [7] and some other.…”

Section: Introductionmentioning

confidence: 99%

“…[3,4] Therefore significant efforts are focused at the development of solid base catalysts for butanal condensation. The catalysts reported so far include MgO, SrO, [3,5] alkali-exchanged zeolites, [6] NiÀ Ce doped alumina [7] and some other. [8] These catalysts have high selectivity towards 2-EN (76-92 %), however they show fast deactivation, resulting from deposition of heavy aldol oligomers and strongly bonded carboxylates on the catalysts surface.…”

Section: Introductionmentioning

confidence: 99%

“…Herein we report on the first implementation of Zr-BEA zeolites for self-condensation of butanal. The paper aims to clarify the main reaction pathways leading to target and side products over this catalyst, to determine the reactivity of different Lewis sites of Zr-BEA including fully condensed closed sites Zr(OSi) 4 and partially hydrolyzed open Zr(OSi) 3 (OH) and to establish the main directions for further catalyst improvement.…”

Section: Introductionmentioning

confidence: 99%

“…The main industrial route for its production involves, butanal condensation towards 2‐ethyl‐2‐hexenal (2‐EN) in the presence of aqueous alkali and its hydrogenation towards final product over Cu−Ni catalysts . This route however has serious drawbacks: i) corrosion of the equipment, ii) formation of by‐products such as sodium butanoate or higher molecular weight species resulted from deeper 2‐EN condensation; iii) extensive production of organic and alkali contaminated wastes . Therefore significant efforts are focused at the development of solid base catalysts for butanal condensation.…”

Section: Introductionmentioning

confidence: 99%

“…The catalysts reported so far include MgO, SrO, alkali‐exchanged zeolites, Ni−Ce doped alumina and some other . These catalysts have high selectivity towards 2‐EN (76–92 %), however they show fast deactivation, resulting from deposition of heavy aldol oligomers and strongly bonded carboxylates on the catalysts surface . Relatively high reaction temperature is required to increase catalyst stability and to facilitate products desorption.…”

Section: Introductionmentioning

confidence: 99%

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Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

2019

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Butanal conversion has been studied over Zr‐BEA zeolites with different amount of partially hydrolyzed open Zr‐sites and fully condensed closed sites. The kinetic study pointed that the main reaction pathway of butanal conversion involves its self‐condensation into 2‐ethyl‐2‐hexenal (2‐EN), the selectivity to 2‐EN being within 80–85 %. Besides, small amounts of 1‐butanol and butanoic acid are formed via Cannizzaro disproportionation of butanal. Secondary reactions include butanoic acid ketonization to 4‐heptanone and esterification to butyl butanoate and tandem hydrogenation/dehydration of 2‐EN into octadienes. A number of techniques, including FTIR spectroscopy of adsorbed CO, pyridine, 2,6‐di‐tert‐butylpyridine (DTBPy), TPD of isopropylamine and selective poisoning with DTBPy were applied for characterization of Zr‐sites and elucidation of their activity. Open Zr‐sites were found to be more active with respect to closed Zr‐sites in butanal condensation: the TOF values estimated at 433 K being 1.4 s−1 for open Zr‐sites and 0.6 s−1 for closed sites. On the contrary, selectivity into 2‐EN was similar for open and closed sites. The results point that Zr‐BEA catalysts with enhanced content of open sites are perspective catalysts for the selective synthesis of 2‐EN.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

2019

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TiO₂-Catalyzed n-Valeraldehyde Self-Condensation Reaction Mechanism and Kinetics

Zhao

et al. 2017

ACS Catal.

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The mechanism of a TiO2-catalyzed n-valeraldehyde self-condensation reaction was first investigated using in situ Fourier transform–infrared spectroscopy (FT-IR) analysis. The result shows that the n-valeraldehyde molecule is adsorbed in two ways separately to Ti4+ and Ti–OH active sites: one involving a strong interaction between the surface Ti4+ and the carbonyl oxygen of n-valeraldehyde molecule, causing a red shift of ν(CO) and the other involving an interaction between the TiO2 surface hydroxyl group Ti–OH and the carbonyl oxygen of n-valeraldehyde molecule via a hydrogen bond, causing a significant shift of Ti–OH peaks to a lower wavenumber. On the basis of the in situ FT-IR analysis, a TiO2-catalyzed n-valeraldehyde self-condensation reaction mechanism was proposed. In the process of n-valeraldehyde adsorption, the infrared characteristic peaks of 2-propyl-3-hydroxyheptanal were not observed, indicating that the dehydration of 2-propyl-3-hydroxyheptanal to 2-propyl-2-heptenal proceeded very quickly. In the process of desorption of products, the infrared characteristic peaks of carboxylates were detected on the surface of TiO2, suggesting that n-pentanoic acid is generated in the reaction system. In addition, we speculate that n-pentanoic acid has a strong interaction with the surface of TiO2 and the generated carboxylates are hardly desorbed, leading to the deactivation of TiO2 catalyst. In order to get a better understanding of the process of TiO2-catalyzed n-valeraldehyde self-condensation, the liquid-phase reaction was monitored in real time by an in situ IR (React-IR). In the whole course of the reaction, 2-propyl-3-hydroxyheptanal was not detected, confirming that this intermediate cannot exist stably, not only on the TiO2 surface but also in the reaction liquid. In order to further verify the reaction mechanism and to confirm the rate-determining step, several possible Langmuir–Hinshelwood models were assumed. By the model identification, the Langmuir–Hinshelwood model with the surface reaction as the rate-determining step is found to be the most probable one.

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Low-Temperature Activation Conditions for PAMAM Dendrimer Templated Pt Nanoparticles

Singh

Chandler

2005

Langmuir

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Surface immobilized polyamidoamine (PAMAM) dendrimer templated Pt nanoparticles were employed as precursors to heterogeneous catalysts. CO oxidation catalysis and in situ infrared spectroscopy were used to evaluate conditions for dendrimer removal. Infrared spectroscopy showed that PAMAM dendrimer amide bonds begin decomposing at temperatures as low as 75°C. Although the amide stretches are completely removed after 3 h of oxidation at 300°C, 16 h were required to reach maximum catalytic activity. Further treatment under oxidizing or reducing atmospheres did not cause substantial changes in activity. Infrared spectroscopy of the activated materials indicated that organic residues, probably surface carboxylates, are formed during oxidation. These surface species passivate the Pt NPs, and their removal was required to fully activate the catalyst. Substantially less forcing activation conditions were possible by employing a CO/O2/He oxidation treatment. At appropriate temperatures, CO acts as a protecting group for the Pt surface, helping to prevent fouling of the nanoparticle by organic residues. CO oxidation catalysis and infrared spectroscopy of adsorbed CO indicated that the low temperature activation treatment yielded supported nanoparticles that were substantially similar to those prepared with more forcing conditions.

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23-P-23 - Catalytic in-situ infrared spectroscopic study of n-butyraldehyde aldol condensation

Cited by 3 publications

References 0 publications

Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

TiO₂-Catalyzed n-Valeraldehyde Self-Condensation Reaction Mechanism and Kinetics

Low-Temperature Activation Conditions for PAMAM Dendrimer Templated Pt Nanoparticles

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23-P-23 - Catalytic in-situ infrared spectroscopic study of n-butyraldehyde aldol condensation

Cited by 3 publications

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Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

Selective Self‐Condensation of Butanal over Zr‐BEA Zeolites

TiO2-Catalyzed n-Valeraldehyde Self-Condensation Reaction Mechanism and Kinetics

Low-Temperature Activation Conditions for PAMAM Dendrimer Templated Pt Nanoparticles

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Product

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TiO₂-Catalyzed n-Valeraldehyde Self-Condensation Reaction Mechanism and Kinetics