Continuous-flow chemoselective reduction of cyclohexanone in a monolithic silica-supported Zr(OPri)4 multichannel microreactor

Ciemięga, Agnieszka; Maresz, Katarzyna; Mrowiec-Białoń, Julita

doi:10.1016/j.micromeso.2017.06.023

Cited by 11 publications

(9 citation statements)

References 36 publications

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“…Battilocchio et al reported the protocol for synthesizing various alcohols from aromatic and aliphatic carbonyl compounds using a packed-bed reactor filled with zirconium hydroxide catalyst [16]. In our previous works [17][18][19], we demonstrated excellent activity of zirconium-doped silica monolithic microreactors in cyclohexanone reductions and their improved performance compared with the batch process. It was shown that zirconium species terminated with propoxy ligands featured the highest activity in MPV reduction among various Lewis centers immobilized onto monoliths' surfaces used as reactive cores in microreactors.…”

Section: Resultsmentioning

confidence: 74%

“…The characterization of siliceous monolithic microreactors functionalized with zirconium species and their catalytic properties were described in our previous papers [17,18]. Kinetic studies were performed in the microreactors featured by the exceptionally low back-pressure.…”

Section: Resultsmentioning

confidence: 99%

“…The monoliths were functionalized with zirconium propoxide to obtained Lewis acid sites on the silica surface. The zirconium cations were terminated by propoxy/hydroxo ligands, which appeared to be very active catalytic centers [18,19]. The Inexpensive and non-toxic hydrogen donors and catalysts, mild reaction conditions, and exceptional chemoselectivity render this method of reduction favorable over alternatives.…”

Section: Resultsmentioning

confidence: 99%

“…The monoliths were functionalized with zirconium propoxide to obtained Lewis acid sites on the silica surface. The zirconium cations were terminated by propoxy/hydroxo ligands, which appeared to be very active catalytic centers [18,19]. The concentration of zirconium, determined by ICP MS analysis, was 7.03 wt % (in relation to the mass of silica support) in all studied microreactors.…”

Section: Resultsmentioning

confidence: 99%

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Selective Reduction of Ketones and Aldehydes in Continuous-Flow Microreactor—Kinetic Studies

2018

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Abstract:In this work, the kinetics of Meerwein-Ponndorf-Verley chemoselective reduction of carbonyl compounds was studied in monolithic continuous-flow microreactors. To the best of our knowledge, this is the first report on the MPV reaction kinetics performed in a flow process. The microreactors are a very attractive alternative to the batch reactors conventionally used in this process. The proposed micro-flow system for synthesis of unsaturated secondary alcohols proved to be very efficient and easily controlled. The microreactors had reactive cores made of zirconium-functionalized silica monoliths of excellent catalytic properties and flow characteristics. The catalytic experiments were carried out with the use of 2-butanol as a hydrogen donor. Herein, we present the kinetic parameters of cyclohexanone reduction in a flow reactor and data on the reaction rate for several important ketones and aldehydes. The lack of diffusion constraints in the microreactors was demonstrated. Our results were compared with those from other authors and demonstrate the great potential of microreactor applications in fine chemical and complex intermediate manufacturing.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The monoliths were functionalized with zirconium propoxide to obtained Lewis acid sites on the silica surface. The zirconium cations were terminated by propoxy/hydroxo ligands, which appeared to be very active catalytic centers [18,19]. The concentration of zirconium, determined by ICP MS analysis, was 7.03 wt % (in relation to the mass of silica support) in all studied microreactors.…”

Section: Resultsmentioning

confidence: 99%

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Selective Reduction of Ketones and Aldehydes in Continuous-Flow Microreactor—Kinetic Studies

2018

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“…Next, in a rare study of the effect of pore structure, three MMRs (4.5 × 40 mm rods), labeled M1-M3, activated with sulfonic groups and possessing the same bimodal pore architecture, yet macro-and mesopores of different sizes, were compared in a continuous-flow synthesis of n-butyl actetate, with a packed-bed reactor filled with Amberlyst 15 used as the benchmark (Ciemięga et al, 2017b). While the pore structure of M1 was similar to that in Koreniuk et al (2015b), other monoliths possessed much smaller flow-through (macro)pores: 4-6 (M2) and 1.3 µm in size (M3) (cf.…”

Section: Performance Of Monolithic Microchannel Reactors Silica Monolithic Microchannel Reactors For Acid-catalyzed Reactionsmentioning

confidence: 99%

Catalytic Functionalized Structured Monolithic Micro-/Mesoreactors: Engineering, Properties, and Performance in Flow Synthesis: An Overview and Guidelines

et al. 2021

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In this review article, we first discussed the development of silica monoliths with hierarchical macro-/mesopore structure and their potential figures of merit as continuous-flow micro-/mesoreactors of up to 30 ml working volume. Making use of the flow hindrance of different pore structures seen from the Darcy law perspective, we discriminated four structures of the monoliths (M1–M4). We then summarized the most important results, mainly from our studies of continuous-flow structured monolithic reactors and rotating bed reactors (RBRs) filled with structured pellets, activated with various catalytic entities and enzymes. The results show that an increase in the flow rate and thus velocity in reactors activated with more conventional catalytic sites has no or a minor positive effect on the apparent reaction rate. On the contrary, in those with the most open structure (M1) and functionalized with enzymes, it could increase by more than two orders of magnitude even at low overpressures. The production systems worked stably for at least 200 h. To conclude, the synthetic system made of the hierarchically structured monoliths, or RBRs filled with structured catalytic pellets, lay the foundation for a new platform for the high-yield production of a wide variety of specialty chemicals, even on a multikilogram scale, in a safe and sustained manner.

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A Continuous‐Flow Microreactor for Knoevenagel Condensation of Ethyl Cyanoacetate with Benzaldehyde: The Effect of Grafted Amino Groups on Catalytic Activity

2023

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Ethyl α‐cyanocinnamate was synthesized in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate in flow monolithic microreactor of 0.63 cm3 volume. The catalytically active core was made of silica monolith modified with various amine group precursors. Structural properties of the support, surface density of NHx groups, and catalytic activity were investigated. It was found that the poly‐ or di‐amine groups attached to the silica surface appeared to be more effective than the aminopropyl groups. Microreactors grafted with diamine functional groups, accompanied by hydrophobic methyl groups, showed the highest activity and stability. It was proved that the decisive role on the activity of catalysts was exerted by the presence of primary amines in diamine chain. The reaction conditions were optimized and it was found that almost full substrate conversion could be achieved in 6 min at 50 °C in the microreactor with low concentration of diamine groups equal to 0.33 mmol g−1.

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Continuous-flow chemoselective reduction of cyclohexanone in a monolithic silica-supported Zr(OPri)4 multichannel microreactor

Cited by 11 publications

References 36 publications

Selective Reduction of Ketones and Aldehydes in Continuous-Flow Microreactor—Kinetic Studies

Selective Reduction of Ketones and Aldehydes in Continuous-Flow Microreactor—Kinetic Studies

Catalytic Functionalized Structured Monolithic Micro-/Mesoreactors: Engineering, Properties, and Performance in Flow Synthesis: An Overview and Guidelines

A Continuous‐Flow Microreactor for Knoevenagel Condensation of Ethyl Cyanoacetate with Benzaldehyde: The Effect of Grafted Amino Groups on Catalytic Activity

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