Intergrowth variants

Experiments to further demonstrate the critical role of extraframework Al, or another polyvalent cation, have recently been carried out in our laboratory (19.20). A series of faujasite-type zeolites was prepared that had Alf concentrations between 21 and 54 per u.c. At the low end of the range, AHF was used to remove the framework Al, and an H-ZSM-20 zeolite with 42 Alf/u.c. was synthesized. ZSM-20 is an intergrowth of the cubic faujasite structure and the hexagonal variant know as Breck s structure six (BSS) (21). Thus, it is a faujasite-like material. The catalytic activities of these zeolites for hexane cracking are compared in Figure 5 (lower data set) with the activities of zeolites prepared by steaming or by treatment with SiClA (upper data set). The solid lines represent N(0) distributions. The samples without extraframework Al exhibited very modest activity, even though some of them had a favorable N(0) concentration. 

Figure 9. Powder X-ray dif action data for four zeolites with, respectively, the cubic FAU-ftamework (a), the EMT-framewoik (a hexagonal variant - (d)), and with varying degrees of intergrowth between the two end member structure types (b and c).

The structure types Ce2(Gao.9Geo.i)7 and La2Ali+xGe6 t are the vacancy variant of the orthorhombic SmNiGe3 and can be considered as an intergrowth of AIB2-, deformed Po- and partially vacant BaAl4-type slabs. 

---