Preparation of zeolite coated substrates

Zeolite-coated substrates, and particularly magnetizable particles suitable for use in a magnetically stabilized fluidized bed, are prepared by introducing the substrate, preferably magnetizable particles such as magnetite or iron, into a a reaction mixture for forming a zeolite having adsorbent properties, such as zeolite Y, heating the reaction mixture and mixing so that there is relative movement of the substrate within the reaction mixture such that the zeolite is preferentially formed as a coating on the substrate.