THE ROLE OF THE TEMPLATE IN DIRECTING THE SI DISTRIBUTION IN SAPO ZEOLITES

X-ray diffraction and Al-27 and Si-29 MAS NMR are used to study the interaction of the templates (morpholine or TEAOH) with the SAPO-34 framework (chabasite structure) and to characterize the distribution of Si in the lattice. The interaction of the template with Si-O-Al bonds suggests the formation of penta- and hexacoordinated Al. Specific limits of Si contents (x(Si)) determine areas where Si(4A1) species are isolated (Si(4Al,9P)) or nonisolated (Si(4Al,nP,mSi)) or where Si forms islands. The two main parameters involved are the upper charge introduced by the template (b) and the upper x(Si) values (d) derived from topology, to have isolated Si, Two main cases of the distribution of Si are whether b < d or b > d. The results obtained for SAPO-34 are extended to any other SAPO.