N. Shigemoto et al., CHARACTERIZATION OF NA-X, NA-A, AND COAL FLY-ASH ZEOLITES AND THEIR AMORPHOUS PRECURSORS BY IR, MAS NMR AND XPS, Journal of Materials Science, 30(22), 1995, pp. 5777-5783
By fusion with sodium hydroxide followed by a hydrothermal reaction, f
ly ash and Al-enriched fly ash were converted into Na-X and Na-A zeoli
tes, respectively. The authentic Na-X, Na-A and fly ash zeolites as we
ll as their amorphous precursors have been characterized by IR, Si-29
and Al-27 MAS NMR, XPS/AES, TG, and comparative ion-exchange studies o
f Cs and K with Na in zeolite samples. It appears that the same struct
ural unit with a terminal OH, such as a sodalite unit, was formed in t
he induction period of the hydrothermal reaction for Na-X and Na-A, an
d then cross-linked through D4R and D6R external linkages to build up
the zeolite framework of Na-A and Na-X, respectively.