Abstract: A gas phase catalytic reactor comprising a metal vessel defining a confinement volume in which electromagnetic waves are generated at a frequency greater than 10 MHz. The confinement volume contains a porous catalyst which is heated by the electromagnetic waves and which has a flow of reactive gas passing therethrough. In order to guarantee that the gas reacts only when in contact with the catalyst, a heat exchanger is used to cool the gas suddenly as it leaves the confinement volume.

Abstract: A device for microwave treatment of materials includes a mold (1) used to hold the material (3) to be treated and a microwave generator which is used to apply to the mold (1) the microwave energy necessary for treatment of the material. The mold includes at least two dielectric materials (4,5,6,7) surrounding the material (3) to be treated. The dielectric materials have dielectric permittivities which differ so that the attenuation of one elementary segment of length l located between the points of side z(n-1) and zn of the longitudinal dimension of the material (3) to be treated which includes at least one section broken up into segments of length l, is controlled by the relationship: ##EQU1## in which: .alpha. is the attenuation in the elementary segment in question,.alpha.o is the initial attenuation in the body of the section which includes the elementary segment in question,Po is the microwave power applied to the section, P(n-1) is the microwave power transmitted in the plane of side z(n-1).