Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts
The application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when...
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| Format: | Article |
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MDPI AG
2020-07-01
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| Series: | Catalysts |
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| Online Access: | https://www.mdpi.com/2073-4344/10/7/777 |
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| author | Satoshi Horikoshi Yuuhei Arai Iftikhar Ahmad Clayton DeCamillis Keith Hicks Bob Schauer Nick Serpone |
| author_facet | Satoshi Horikoshi Yuuhei Arai Iftikhar Ahmad Clayton DeCamillis Keith Hicks Bob Schauer Nick Serpone |
| author_sort | Satoshi Horikoshi |
| collection | DOAJ |
| description | The application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when using a strong microwave absorber such as activated carbon (AC) particulates as supports of metal-based catalysts. Two model reactions performed in low boiling point nonpolar solvents are described wherein arc discharges easily occur under the more conventional fixed frequency microwave (FFM) approach: (i) the synthesis of 4-methylbiphenyl (4MBP) by the Suzuki-Miyaura cross-coupling process catalyzed by Pd particles supported on AC particulates (Pd/AC), and (ii) the synthesis of toluene via the dehydrogenation of methylcyclohexane (MCH) catalyzed by Pt particles dispersed on AC particulates (Pt/AC). Contrary to the usage of fixed frequency microwaves (5.85 GHz and 6.65 GHz), the use of VFM microwaves increased the chemical yields of 4MBP {49% versus 5–8% after 60 min} and toluene {89% versus 24% after 10 min} by suppressing the formation of discharges that otherwise occur on the catalyst/AC surface with FFM microwaves. Consequently, relative to the latter approach, the VFM technology is significantly advantageous, especially in reactions with solid conductive catalysts, not least of which are the reduction in power consumption, thus energy savings, and the prevention of potential mishaps. |
| first_indexed | 2024-03-10T18:31:32Z |
| format | Article |
| id | doaj.art-69c87792b3fd40d383b457085a654a66 |
| institution | Directory Open Access Journal |
| issn | 2073-4344 |
| language | English |
| last_indexed | 2024-03-10T18:31:32Z |
| publishDate | 2020-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Catalysts |
| spelling | doaj.art-69c87792b3fd40d383b457085a654a662023-11-20T06:32:26ZengMDPI AGCatalysts2073-43442020-07-0110777710.3390/catal10070777Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive CatalystsSatoshi Horikoshi0Yuuhei Arai1Iftikhar Ahmad2Clayton DeCamillis3Keith Hicks4Bob Schauer5Nick Serpone6Department of Material & Life Science, Faculty of Science and Technology, Sophia University, 7-1, Kioicho, Chiyodaku, Tokyo 102-8554, JapanDepartment of Material & Life Science, Faculty of Science and Technology, Sophia University, 7-1, Kioicho, Chiyodaku, Tokyo 102-8554, JapanLambda Technologies, Inc., Applications Engineering Team, 860 Aviation Parkway, Suite 900, Morrisville, NC 27560, USALambda Technologies, Inc., Applications Engineering Team, 860 Aviation Parkway, Suite 900, Morrisville, NC 27560, USALambda Technologies, Inc., Applications Engineering Team, 860 Aviation Parkway, Suite 900, Morrisville, NC 27560, USALambda Technologies, Inc., Applications Engineering Team, 860 Aviation Parkway, Suite 900, Morrisville, NC 27560, USAPhotoGreen Laboratory, Dipartimento di Chimica, Universita di Pavia, Via Taramelli 10, 27100 Pavia, ItalyThe application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when using a strong microwave absorber such as activated carbon (AC) particulates as supports of metal-based catalysts. Two model reactions performed in low boiling point nonpolar solvents are described wherein arc discharges easily occur under the more conventional fixed frequency microwave (FFM) approach: (i) the synthesis of 4-methylbiphenyl (4MBP) by the Suzuki-Miyaura cross-coupling process catalyzed by Pd particles supported on AC particulates (Pd/AC), and (ii) the synthesis of toluene via the dehydrogenation of methylcyclohexane (MCH) catalyzed by Pt particles dispersed on AC particulates (Pt/AC). Contrary to the usage of fixed frequency microwaves (5.85 GHz and 6.65 GHz), the use of VFM microwaves increased the chemical yields of 4MBP {49% versus 5–8% after 60 min} and toluene {89% versus 24% after 10 min} by suppressing the formation of discharges that otherwise occur on the catalyst/AC surface with FFM microwaves. Consequently, relative to the latter approach, the VFM technology is significantly advantageous, especially in reactions with solid conductive catalysts, not least of which are the reduction in power consumption, thus energy savings, and the prevention of potential mishaps.https://www.mdpi.com/2073-4344/10/7/777variable frequency microwavesfixed frequency microwavesmicrowave chemistryarc dischargessolid catalystsorganic synthesis |
| spellingShingle | Satoshi Horikoshi Yuuhei Arai Iftikhar Ahmad Clayton DeCamillis Keith Hicks Bob Schauer Nick Serpone Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts Catalysts variable frequency microwaves fixed frequency microwaves microwave chemistry arc discharges solid catalysts organic synthesis |
| title | Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts |
| title_full | Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts |
| title_fullStr | Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts |
| title_full_unstemmed | Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts |
| title_short | Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts |
| title_sort | application of variable frequency microwaves in microwave assisted chemistry relevance and suppression of arc discharges on conductive catalysts |
| topic | variable frequency microwaves fixed frequency microwaves microwave chemistry arc discharges solid catalysts organic synthesis |
| url | https://www.mdpi.com/2073-4344/10/7/777 |
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