Structure-Direction by T-Atoms

It is also remarkable that the crystaUisation of TNU-7 depends critically on the presence of Ga in the synthesis mixture, as well as on its content. As seen in Table variation of the Ga concentration 

The phase appearing first is the major phase, and the product obtained in a trace amount is given in parentheses ANA, analcime MAZ, mazzite MOR, mordenite MER, merlinoite FER, ferrierite L, unknown but probably layered phase. 

A small amount (2 wt% of silica in the synthesis mixture) of the calcined gallosilicate with Si/ Ga = 2.60 or aluminosilicate mazzite with Si/Al = 3.17 prepared in the presence of tetramethy-lammonium ion was added as seeds prior to heating at 150 °C for 3 days. 

Structural chemical zoning in this gallosilicate zeolite, i.e. an alternation of Ga-rich MAZ and Ga-poor MOR layers in its framework, probably due to the local fluctuation of composition of the mother liquor caused by the crystallisation of the previous layer. 

Ge is directly below Si in the periodic table, and both SiOi and GeOz may crystallise as quartz, cristobalite and rutile phases. This tetravalent atom can adopt coordination numbers of 4-6 in contrast to Si that is normally tetrahedral in its oxides, therefore, it is not surprising that Ge substitution into several zeolite frameworks including THO, FAU, LTA and PHI topologies was successfully attempted five decades ago. Until the late 1990s, however, no attempts to synthesise new microporous germa-nate frameworks in which all Ge atoms are tetrahedral had been successful.f  

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