Microwave-assisted preparation of zeolite K–H from alumatrane and silatrane

Abstract

Using alumatrane and silatrane as sources of silica and alumina, respectively, and potassium hydroxide as the hydrolytic agent, a very high purity K-loaded zeolite was synthesized for the first time, via sol–gel processing and microwave heating techniques. Because of the bulky trialkoxyamine ligands, which shield the silicon and aluminium atoms, both alumatrane and silatrane are inert to hydrolysis, and can therefore be investigated over a wide pH range. By fixing the composition at SiO 2:0.1Al 2O 3:3K 2O:410H 2O and the microwave heating temperature at 150 °C for 240 min, based on x-ray diffraction analysis, the synthesized product is a K–H zeolite of hitherto unknown structure, designated as PPC-ZM-1. The Si:Al:K ratio of the synthesized product is 1.98:1:0.82, and the polycrystalline morphology resembles flower petals. The Si:Al loading ratio, microwave heating temperature and K 2O:SiO 2 ratio influence the morphology of the product. In addition, the K 2O:SiO 2 ratio also influences the microwave heating time to achieve complete crystallinity. Prolonged heating after obtaining crystalline product results in a change of the polycrystalline morphology to longer, more densely packed crystals.