<i>In situ</i> Raman monitoring of dielectric-heating-enhanced freeze-drying under different electromagnetic wave frequencies

Tsubaki, Shuntaro; Matsuzawa, Toshihiro; Fujii, Satoshi; Suzuki, Eiichi; Kanamori, H.; Hoshino, Tetsuya; Hosoda, Saichi; Wada, Yuji

doi:10.1039/c9ra00981g

Cited by 3 publications

(3 citation statements)

References 26 publications

(25 reference statements)

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“…35 More recently, we have demonstrated changes in the structure of water during freeze-drying under MW and radio frequency (RF) dielectric heating by monitoring the O−H stretching band of water molecules associated with the hydrogen bonding network. 36 In this paper, we investigate the state of chemical bonding and the deposition of carbon on the surface of the catalyst during the catalytic dehydration of 2-propanol using WO 3 to understand the mechanism by which MW irradiation enhances the catalytic reaction. The inter-and intramolecular dehydration of 2-propanol forms diisopropyl ether and propylene, respectively, depending on the reaction temperature; therefore, this reaction is suitable for evaluating the MW heating effect.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Horikoshi et al used Raman spectroscopy to directly observe the structural changes on the surface of the TiO 2 catalyst during the photoinduced degradation of organic molecules, which was enhanced under MW irradiation . More recently, we have demonstrated changes in the structure of water during freeze-drying under MW and radio frequency (RF) dielectric heating by monitoring the O–H stretching band of water molecules associated with the hydrogen bonding network …”

Section: Introductionmentioning

confidence: 99%

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Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Tsubaki

Matsuzawa

Suzuki

et al. 2020

Ind. Eng. Chem. Res.

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Operando Raman spectroscopy was performed to understand the mechanism of a microwave (MW)-enhanced fixed-bed catalytic reaction. An MW operando Raman spectroscopy system was constructed by integrating a Raman spectroscopy probe (785 nm) with a single-mode (TM110) MW cavity resonator equipped with a semiconductor MW generator. MW heating enhanced the dehydration of 2-propanol to diisopropyl ether and propylene by +54 to +60% under the air flow condition. In the argon flow condition, the conversion of 2-propanol was further enhanced by +71 to +83% with >99.9% selectivity toward propylene when MW heating was used. Operando Raman spectroscopy revealed that MW irradiation enhances the reduction of the WO3 surface and exhibits intense light emission, especially under the argon flow condition. The enhanced generation of WO3–x species on the surface of the WO3 catalyst should be, therefore, a key factor in the enhancement of the dehydration of 2-propanol under MW irradiation.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Tsubaki

Matsuzawa

Suzuki

et al. 2020

Ind. Eng. Chem. Res.

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“…CO 2 -rich amine solutions (30 wt %, 5.0 mL) were added to a quartz test tube and placed in the maximum electric field ( E -max) of the waveguide (915 MHz, 2.45 GHz) and parallel-plate-type applicator (Figure S3). , Dielectric heating started after replacing the inside of the reaction system with Ar. A constant MW and RF power of 40 W was applied for 15 min.…”

Section: Results and Discussionmentioning

confidence: 99%

Insights into the Dielectric-Heating-Enhanced Regeneration of CO₂-Rich Aqueous Amine Solutions

Tsubaki

Furusawa

Yamada

et al. 2020

ACS Sustainable Chem. Eng.

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Microwaves (MW) and radio frequency (RF) dielectric heating were used to facilitate the regeneration of CO 2rich amine solutions, and the mechanism of the rate enhancement by dielectric heating was discussed. Dielectric measurements of aqueous solutions of monoethanolamine (primary amine), 2-(ethylamino)ethanol (secondary amine), and N-methyl diethanolamine (tertiary amine) revealed that the formation of carbamate and bicarbonate ions by CO 2 absorption improves the dielectric loss tangent. Dielectric heating by MWs (2.45 GHz, 915 MHz) and RF (200 MHz) was compared to facilitate regeneration of the CO 2 -rich amine solution at a constant power of 40 W. The CO 2 release rate was the highest at 2.45 GHz in all aqueous amine solutions, which was 1.47 to 1.74 times that of conventional heating by an oil bath operated at 120 °C. However, the CO 2 release rate decreased as the frequency decreased to 915 and 200 MHz. Electromagnetic field simulation suggested that CO 2 release was enhanced owing to the generation of a more intense electric field at 2.45 GHz than at lower frequencies.

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Nondestructive 3D imaging and quantification of hydrated biofilm matrix by confocal Raman microscopy coupled with non-negative matrix factorization

et al. 2022

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In situ Raman monitoring of dielectric-heating-enhanced freeze-drying under different electromagnetic wave frequencies

Abstract: We studied the effect of dielectric heating on the enhancement of freeze-drying by electromagnetic waves (EMWs) under different frequencies: 2.45 GHz microwaves (MWs), and 27 and 200 MHz radio frequencies (RFs).

Cited by 3 publications

References 26 publications

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Insights into the Dielectric-Heating-Enhanced Regeneration of CO₂-Rich Aqueous Amine Solutions

Nondestructive 3D imaging and quantification of hydrated biofilm matrix by confocal Raman microscopy coupled with non-negative matrix factorization

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In situ Raman monitoring of dielectric-heating-enhanced freeze-drying under different electromagnetic wave frequencies

Abstract: We studied the effect of dielectric heating on the enhancement of freeze-drying by electromagnetic waves (EMWs) under different frequencies: 2.45 GHz microwaves (MWs), and 27 and 200 MHz radio frequencies (RFs).

Cited by 3 publications

References 26 publications

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO3

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO3

Insights into the Dielectric-Heating-Enhanced Regeneration of CO2-Rich Aqueous Amine Solutions

Nondestructive 3D imaging and quantification of hydrated biofilm matrix by confocal Raman microscopy coupled with non-negative matrix factorization

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Resources

About

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Operando Raman Spectroscopy of the Microwave-Enhanced Catalytic Dehydration of 2-Propanol by WO₃

Insights into the Dielectric-Heating-Enhanced Regeneration of CO₂-Rich Aqueous Amine Solutions