TEMPO-functionalized mesoporous silica particles as heterogeneous oxidation catalysts in flow

Schulze, Julia S.; Migenda, Julia; Becker, Maximilian; Schuler, Sören M. M.; Wende, Raffael C.; Schreiner, Peter R.; Smarsly, Bernd M.

doi:10.1039/c9ta12416k

Cited by 29 publications

(23 citation statements)

References 52 publications

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“…For instance, recently we showed that TEMPOfunctionalized mesoporous silica particles can generally be used as oxidative catalyst system in flow. [59] The results of the present study indicate that enhanced catalytic performance might be achieveable for such demanding organocatalysts by using meso-macroporous monoliths.The complete synthesis of the reactor gives control over each step, so the material can be optimized for various catalysts and reactions by studying the effects of individual parameters like porosity and degree of functionalization to achieve a deeper understanding of continuous flow catalysis with porous silica materials.…”

Section: Chemcatchemmentioning

confidence: 62%

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

et al. 2022

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We report the immobilization of 4-dimethylaminopyridine (DMAP), a versatile organocatalyst for sterically demanding esterifications, on mesoporous silica particles and macromesoporous silica monoliths, both possessing optimized properties for continuous flow synthesis. An alkyne-functionalized DMAP derivative was immobilized via click chemistry; the materials were characterized by physisorption analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and elemental analysis. While silica particles were functionalized in batch and packed into a packed-bed reactor, monoliths were cladded with a polyether ether ketone (PEEK) tube after sol-gel synthesis and functionalized in a circulating flow process. Samples with three different catalyst loadings were prepared, in order to study the impact of the catalyst amount on the mesopore space as well as the catalytic performance. In continuous flow experiments, complete conversion of 1-phenylethanol to phenylethylacetate was achieved with both materials and short contact times. Monoliths exhibited far lower pressures than packed bed reactors (7 bar at a flow rate of 1 mL min À 1 ) and reached turnover rates up to 9.3x10 À 2 s À 1 , which is almost twice as high as a comparable batch experiment. The absence of diffusion limitations in monoliths made investigations on reaction kinetics with microkinetics-dominated experiments possible. This study demonstrates that all properties needed for a successful transfer of immobilized organocatalysts to sophisticated flow syntheses with complex organocatalysts can be met with functionalized meso-macroporous monoliths.

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Section: Chemcatchemmentioning

confidence: 62%

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

et al. 2022

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“…In 2020, Schulze et al synthesized an organo-heterocatalyst by post-modifying a silica material (LiChrospher s Si 100, particle size 5 mm) to generate azidefunctionalized silica particles, which were further modified by applying click-chemistry with propargyl ether-TEMPO. 41 This TEMPO-modified mesoporous silica-based heterocatalyst showed a good performance for the conversion of benzyl alcohol to benzaldehyde in an HPLC column reactor. However, diacetoxyiodobenzene (DAIB), a mild secondary oxidising agent, was chosen as a co-catalyst to regenerate TEMPO during the reaction.…”

Section: Synthesis Of Organically Functionalized Mesoporous Silicasmentioning

confidence: 94%

Porous organic–inorganic hybrid materials for catalysis, energy and environmental applications

et al. 2022

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“…Beneficially, the heterogeneous catalyst remains highly active even after hours of operation (up to 9 hours). Other TEMPO-immobilised systems have also been developed; Sato and Okuno et al explored immobilisation on a polyethylene–polyacrylic acid polymer, and Smarsly et al using mesoporous silica particles [ 324 – 325 ]. Each support strategy offers different processing advantages and limitations based upon pressure drop, loading and ease of preparation.…”

Section: Reviewmentioning

confidence: 99%

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

Gambacorta¹,

Sharley²,

Baxendale³

2021

Beilstein J. Org. Chem.

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Due to their intrinsic physical properties, which includes being able to perform as volatile liquids at room and biological temperatures, fragrance ingredients/intermediates make ideal candidates for continuous-flow manufacturing. This review highlights the potential crossover between a multibillion dollar industry and the flourishing sub-field of flow chemistry evolving within the discipline of organic synthesis. This is illustrated through selected examples of industrially important transformations specific to the fragrances and flavours industry and by highlighting the advantages of conducting these transformations by using a flow approach. This review is designed to be a compendium of techniques and apparatus already published in the chemical and engineering literature which would constitute a known solution or inspiration for commonly encountered procedures in the manufacture of fragrance and flavour chemicals.

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TEMPO-functionalized mesoporous silica particles as heterogeneous oxidation catalysts in flow

Abstract: TEMPO was immobilized on continuous-flow-optimized mesoporous silica particles and a TEMPO/DAIB mediated oxidation followed by Knoevenagel condensation was investigated.

Cited by 29 publications

References 52 publications

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

DMAP Immobilized on Porous Silica Particles and Monoliths for the Esterification of Phenylethanol in Continuous Flow

Porous organic–inorganic hybrid materials for catalysis, energy and environmental applications

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

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