Abstract:

NaY zeolite was in-situ synthesized with kaolin microspheres as raw material.The effects of synthesis conditions on the crystallinity of Y zeolite were investigated in detail,such as mass ratio of solid-to-liquid,amount-of-substance ratio of alkali-to-silica,mass ratio of metakaolin to fully calcined kaolin microspheres and silicon sources.Results showed that the crystallinity of Y zeolite could be improved by properly reducing solid-to-liquid ratio and increasing alkali-to-silica ratio.But with the decrease of the solid-to-liquid ratio and the increase of the alkali-to-silica ratio,the attrition index of the products and the amount-of-substance ration of silica to alumina of Y zeolite decreased gradually.The crystallinity of Y zeolite could be increased to 28% with the mass ratio of metakaolin to fully calcined kaolin microspheres was 1∶4.However,with the further increase of the mass ratio of metakaolin to fully calcined kaolin microspheres,the crystallinity of Y zeolite changed little.Under the condition of the mass ratio of metakaolin to fully calcined kaolin microspheres of 2∶3 and solid-liquid ratio of 0.38 and using silica aerogel as partial silica source,the as-synthesized product had 37% Y crystallinity and its SiO₂/Al₂O₃ was 4.7.Also,the product showed good attrition index with 0.9%.

Key words: kaolin, NaY zeolite, in-situ crystallization