ZSM-22 (TON) can be produced from a potassium based 1,6 hexamethylenediamin
e (1,6 HDM) synthesis mixture. However, ZSM-34 (an OFF/ERI intergrowth) is
synthesized from the same synthesis mixture with the addition of a source o
f sodium either from colloidal silica combined with sodium hydroxide or fro
m sodium silicate. NMR analyses of the as-synthesized zeolite samples deter
mined the presence of a carbonyl species for all of the ZSM-34 samples, but
not for any preparations that produced ZSM-22. The carbonyl species was pr
esent in all ZSM-34 preparations regardless of the diamine used (NH2CnH2nNH
2 for n = 4, 6, 8, or 10) and was present only after the synthesis mixture
was heated above the ambient temperature (even though the gel was still amo
rphous). The source of the carbonyl may be obtained from the reaction of ca
rbon dioxide preadsorbed in the basic sodium solution with the diamine to f
orm a carbamic acid. Molecular modeling studies, based on pore filling, cal
culated a favorable fit of the carbamic species within the pore system of t
he Erionite suggesting a reason for the formation of the OFF/ERI intergrowt
h. (C) 2000 Elsevier Science B.V. All rights reserved.