HYDROTHERMAL METHOD FOR THE DIRECT SYNTHESIS OF ZEOLITES FROM FLY ASH.

摘要

The present invention describes a hydrothermal method for promoting the direct zeolitization of fly ash obtained from the thermoelectric industry as a byproduct of the mineral coal. The fly ashes include a total content of 80% of Si02+A1203, a low content of thermodynamically stable crystalline species such as quartz, mullite, calcite and a high content of amorphous material (79.5%), the same allowing the ashes to be specially reactive with a hydroxide of an alkaline and/or alkaline earth metal, so that performing the zeolitization by a method herein described. The method of the present invention comprises the reaction of the fly ashes under hydrothermal conditions with a metallic hydroxide in a predetermined ratio; the reagent mixture is directly subjected to a hydrothermal process with or without being stirred at a temperature of from about 175°C and for a period of time of up to 24 hours. The zeolites thus obtained are washed with deionised water, dried and packed in a sealed conta ined to be preserved. The method of the invention is useful for obtaining analcime zeolites and w zeolite, both as unique crystalline species, as well as zeolite P and ABW in a mixture with an amorphous phase.