Application of Microwave Energy in Chemical Engineering · 2014-08-13 · Application of Microwave Energy in Chemical Engineering Ji Un Im, Seong-Soo Hong, Gun-Dae Lee and Seong Soo

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Korean Chem. Eng. Res., Vol. 42, No. 5, October, 2004, pp. 485-493

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Application of Microwave Energy in Chemical Engineering

Ji Un Im, Seong-Soo Hong, Gun-Dae Lee and Seong Soo Park†

Division of Applied Chemical Engineering, Pukyong National University, San 100, Yongdang-dong, Nam-gu, Busan 608-739, Korea

(Received 2 September 2004; accepted 15 September 2004)

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Abstract − The fast and convenient heating of foodstuffs in microwave ovens is routinely used in the common life.Recently, many researchers have recognized other potential applications for this method of heating, then have appliedthe rapid and selective heating associated with microwave technology to a number of useful processes. With the tool ofthe basic information required to apply the microwave technology to many processes, this paper reviewed briefly theprinciple and characteristic of microwave heating, the design of microwave unit, the interaction of microwave-matter,and the outlook of future microwave technology. Especially, it is focussed to explain the microwave thermal and non-thermal effects in organic synthesis based on medium effects and mechanistic considerations.

Key words: Microwave, Energy, Polarization, Microwave Effect, Non-thermal, Superheating

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Fig. 1. Electromagnetic spectrum.

Fig. 2. Behaviors of microwaves.

Fig. 3. Trend of publications in organic microwave synthesis.

Fig. 4. Loss tangent with increasing temperature for fused-silica andsoda-lime-silica glasses.

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Korean Chem. Eng. Res., Vol. 42, No. 5, October, 2004

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Table 1. Temperatures of the liquid samples irradiated at the microwavepower of 600 W

SamplesTemperature after

1 min irradiation (oC)Boiling point

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(Debye)

H2O 81 100 5.9EtOH 78 78 5.8n-C5H11OH 106 137 5.7CH3CO2H 110 119 5.6DMF 131 153 10.8n-C6H14 25 98 0.0CCl4 28 77 0.0

Table 2. Temperatures of the solid samples irradiated at the microwavepower of 600 W

Samples Irradiation time (min) Final temperature (oCs)

Al 6 1577C 1 1,283Co 3 1697Cu 7 1228Fe 7 1768Zn 3 1581

CuO 6 1167Cu2O 6 1,012Fe3O4 3 1,258MnO 6 1113MnO2 6 1,287WO3 6 1581ZnO 3 1,270

Fig. 5. Schematic presentation of polarization mechanisms.

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Elastomer ASTM designation ε' ε"

Natural rubber NR 2.35 0.00645Styrene-butadiene SBR 2.45 0.01070Polybutadiene BR - 0.00538Ethylene-propylene EPDM 2.35 0.00670Polyisobutylene IIR 2.35 0.00210Polychloroprene CR 4.00 0.13560Nitrile NMR 2.80 0.05040

Fig. 6. Heating rates of polymers exposed to microwaves.

Fig. 7. The schematic diagram of microwave system.

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Fig. 9. The schematic diagram of industrial microwave system.

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Table 4. A comparison of reaction times and yield in representative reactions using classical and microwave heating

Compound synthesized Procedure followed Reaction time Average yield (%) kmicrowave/kclassical

Hydrolysis of benzamide to benzoic acid in waterC6H5COOH Classical 1 h 90C6H5COOH Microwave 10 min 99 6

Oxidation of toluene to benzoic acid in waterC6H5COOH Classical 25 min 40C6H5COOH Microwave 5 min 40 5

Esterification of benzoic acid with methanolC6H5COOCH3 Classical 8 h 74C6H5COOCH3 Microwave 5 min 76 96

SN2 reaction of 4-cyanophenoxide ion with benzylchloride in methanolNCC6H4OCH2C6H5 Classical 16 h 89NCC6H4OCH2C6H5 Microwave 4 min 93 240NCC6H4OCH2C6H5 Classical 12 h 65NCC6H4OCH2C6H5 Microwave 35 sec 65 1,240

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Table 6. Boiling points of polar solvents

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Fig. 16. The position of the transition state along the reaction coordi-nates.

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Application of Microwave Energy in Chemical Engineering · 2014-08-13 · Application of Microwave Energy in Chemical Engineering Ji Un Im, Seong-Soo Hong, Gun-Dae Lee and Seong Soo