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Thermal Phenomena Under Microwave Field in the Organic Synthesis Processes: Application to the Diels Alder Reaction

Published online by Cambridge University Press:  10 February 2011

R. Saillard ,
M. Poux  and
M. Audhuy-Peaudecerf
R. Saillard
Affiliation:
19 rue Guy de Maupassant 92500 RUEIL MALMAISON, France
M. Poux
Affiliation:
ENSIGC, 18 chemin de la Loge 31078 TOULOUSE CEDEX, France
M. Audhuy-Peaudecerf
Affiliation:
ENSEEIHT, 2 rue Camichel 31071 TOULOUSE CEDEX, France
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Abstract

The influence of the microwave heating on chemical reactions were investigated. The kinetic of the Diels Alder reaction were studied under Microwave irradiation at a frequency of 2.45 GHz in a single mode cavity and were compared to the kinetic obtained by a conventional heating. Experiments were carried out in a liquid solvent in order to have a better control of the medium temperature measurement. In a second part, the presence of a catalytic solid phase was introduced. Some thermal fluctuations which are due to an heterogeneity of the electric field were detected in the medium. They reduce the precision of the results and cause problems of experimental reproducibility. A thermoluminescent material allow a good visualisation of these phenomena.

In addition, the profiles of the electric field intensity were modelled by a 2D finite elements method in our reactor in the presence of a solvent. Despite the small size of the sample and the use of a monomode cavity which both limited the heterogeneities of the medium temperature, we showed a great heterogeneity of the electric field intensity and as a result the heterogeneity of the temperature in our sample.

In order to avoid these phenomena which induce a lack of reproducibility, a stirring device was developed.

The values of the kinetics obtained under the 2 heating modes with the introduction of the stirring device. So, it induces a good control of the medium temperature.

All those investigations prompted us to the conclusion that there is no difference between microwave heating and a classical heating in the studied reaction.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 430: Symposium O – Microwave Processing of Materials V , 1996 , 411
Copyright
Copyright © Materials Research Society 1996

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