Crystallization of zeolite X coatings on stainless steel by microwave heating

The possibility of crystallization of zeolite X coatings on metal plates in a microwave oven was investigated. Characterizations were performed by X-ray diffraction, scanning electron microscopy, laser microscopy and gas adsorption. Crystalline zeolite X coatings with mass equivalent thicknesses of up to about 100 μm could be obtained on stainless steel plates. Heating the reaction mixture by microwaves instead of conventionally resulted in faster crystallization of zeolite X coatings on metal. The yield of zeolite was about 2.5–4.7 fold higher during different earlier periods of synthesis in the presence of microwave irradiation. The utilization of a device, containing graphite having good absorbance of microwaves, which was brought into firm contact with the metal plate, resulted in an increase of the zeolite yield by about 20 %. This indicated that the metal substrate profited from being heated conductively by the mentioned device, rather than being convectively heated by the reaction mixture.