Host: The Society of Chemical Engineers, Japan
Hydrothermal synthesis of faujasite-type (FAU) zeolite using a coal fly ash was investigated while rotating. We discussed that the formation of FAU from coal fly ash was influenced by four synthetic factors as follows; 1) the addition of FAU seeds, 2) the addition of an aluminum source, 3) alkalinity of synthetic mixture and 4) crystallization temperature in the temperature range of 90 to 120°C. The addition of FAU seeds in the synthetic mixture was essential for the formation of FAU, otherwise GIS-type zeolite (GIS), an undesired by-product, was simultaneously formed. Higher alkaline conditions using aqueous NaOH solution (3 N) gave a higher yield of FAU (45.4 wt%). The highest yield of FAU (56.7 wt%) was obtained with the addition of 1.4 mmol (g-coal)-1 of aluminum in 3N-aqueous NaOH solution. A further increasing amount of the addition of aluminum resulted in increasing yields of sodalite (SOD) and LTA-type zeolite (LTA). The induction period of the formation of GIS was longer at the lower crystallization temperature of 90°C.
