Characterization and catalytic activities of faujasites synthesized by using coal fly ash

Abstract

Coal combustion by-product fly ash was converted selectively into faujasite (Y type) zeolite and was used as a catalytic material. The conversion process tried to alleviate the disposal problem of large amounts of fly ash, and turned fly ash into useful materials. Fused fly ash powder and supernatant were used in the synthesis of Y type zeolite. The prepared Na-Y zeolites were characterized and ion-exchanged followed by calcinations to obtain H-Y. The catalytic properties of the solid obtained were evaluated using cumene cracking and compared with those of commercially available (standard) zeolites. It was found that most of the Si and Al components in the fly ash could be effectively transformed into Y type zeolite in the presence of seeds but not the mineral phase, such as mullite. Moreover, the supernatant of the fused powder solution can produce purer faujasites and the sediment can be reused to generate solution for the further preparation of zeolites. Investigation by NMR demonstrated that fusion plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. The H-Y zeolite derived from the supernatant of fly ash solution shows excellent cracking activity compared to that of standard.