New instrumentation for the comprehension of chemical reactions under microwave and classical heating with the aid of a wide frequency band dielectric spectroscopy

¹ Laboratoire de Génie Électrique de Paris (LGEP-Supelec, Paris 6, Paris 11 (CNRS-UMR 8507)), Plateau de Moulon, 91192 Gif-sur-Yvette Cedex, France
² Laboratoire des Réactions Sélectives sur Supports, LRSS, Université Paris-Sud (CNRS UMR 8615), bâtiment 410, 91405 Orsay Cedex, France
³ Laboratoire de l'Interface, des Traitements, de l'Organisation et de la Dynamique des Systèmes, ITODYS, Université Paris 7 (CNRS UPRES A 7086), 2 place Jussieu, 75252 Paris Cedex 05, France

Corresponding author: chevalie@ccr.jussieu.fr

Received: 21 December 2000
Revised: 19 February 2001
Accepted: 5 April 2001
Published online: 15 September 2001

Abstract

An instrumentation system for measuring wide frequency band complex permittivity of a sample submitted to a microwave irradiation has been optimized in order to allow macroscopic temperature measurements. The reaction of saponification of aromatic esters is studied using this instrumentation. We take interest in the behavior of the ionic conductivity phenomenon occurring in the reactive medium during microwave heating, and we compare it with the results obtained under classical heating. We show that the activation energy associated with ionic conductivity is lower when the reaction is performed under microwaves than when it is performed under classical heating. We thus deduce that microwaves act on the reaction advancement as a catalyst, and thus makes the reaction easier.