UTILIZATION OF MICROWAVES IN THE STUDY OF REACTION-KINETICS IN LIQUIDAND SEMISOLID MEDIA

An apparatus, referred to as the microwave kinetics reactor (MWKR), in corporating a microwave-transparent pressure vessel with mechanical mi xing together with a microwave temperature controller, was developed a nd tested. Experiments were performed to determine a safe and practica l operating envelope for the MWKR. Temperatures measured at the center and at the top surface of varying viscosity solutions in the MWKR wer e used to determine the adequacy of mixing when the solutions were hea ted from room temperature to 120-degrees-C and held for a prescribed p eriod of time. The viscosities of the solutions were adjusted by addin g (carboxymethyl)cellulose (CMC) to distilled water. A 2% CMC solution represented the upper viscosity limit to be heated homogeneously in t he apparatus (approximately 2000 cP). To illustrate the usefulness of this apparatus in obtaining kinetic parameters, thiamin hydrochloride degradation kinetics in pea puree were determined at 100, 120, and 130 -degrees-C and compared to those obtained from the literature. The MWK R offers an attractive, efficient, convenient, and accurate alternativ e for the study of reaction kinetics in viscous fluids and semisolids because of its short come-up time and mixing capability. Experimentall y determined kinetic parameters compared very well to those obtained f rom the literature. As expected the kinetics was first-order, with an activation energy, E(a), of 27.0 kcal/mol.