FORMATION PROCESS OF MULLITE FROM NH4-EXCHANGED ZEOLITE A()

Zeolite A (NH4-A) exchanged with NH4+ was used as a precursor of mulli te. NH4-A was dehydrated and deamoniated by heating up to 300-degrees- C and it entered an amorphous state. Mullite crystallized directly fro m the amorphous phase at above 950-degrees-C without forming a spinel phase as an intermediate phase. Since the starting material is zeolite A, which has the tetrahedral framework structure with homogeneous arr angement of Si, Al, and O atoms, these experimental results supported the previous hypothesis proposed for the formation process of mullite.