The development of zeolite catalysts with tailored pore architectures has been central to the success of the modern petrochemical industry. While medium-pore zeolites (e.g., ZSM-5, ZSM-11, ZSM-22, ZSM-35) dominate many industrial processes, large-pore zeolites play an irreplaceable role in reactions involving bulky molecules that cannot fit into 10-MR channels.
ZSM-48 is a large-pore zeolite with the AFI framework and was first reported by Rubin, Chu, and Maxwell (1981) at Mobil Oil Corporation. It was assigned the structure code AFI by the International Zeolite Association (IZA). Unlike its smaller-pore cousins, ZSM-48 features 12-membered ring channels — the largest ring size among common zeolite frameworks — giving it a pore aperture of ~7.3 Å, comparable to zeolite Beta and significantly larger than ZSM-5 (5.5 Å).
The general chemical composition of ZSM-48 is:
with the Si/Al ratio tunable from approximately 5 to infinity, enabling precise control over acidity and hydrophobic character.
| Property | Value |
|---|---|
| Framework type | AFI |
| Channel system | 1D, parallel |
| Pore opening | 7.3 × 7.3 Å (12-MR) |
| Channel dimension | 7.3 × 7.3 Å (elliptical) |
| Cage type | Hexagonal prism |
| Space group | P6/mmm (hexagonal) |
| Si/Al ratio | 5–∞ (tunable) |
| Crystal density | ~1.75 g/cm³ |
| Unit cell parameters | a = 18.9 Å, c = 5.1 Å |
The defining structural feature of ZSM-48 is its one-dimensional channel system composed of 12-membered rings:
However, the strictly one-dimensional nature of the channels means:
