ARGON SORPTION IN ZSM-5

A new physisorption device collects accurate isotherm data at low pressures and low adsorptions. Thus, physisorption isotherms of microporous materials can he determined in fine detail in the region where the first sorbing atoms enter the unit cell of the solid. For argon phvsisorption in ZSM-5 at 87 K, a complex isotherm is observed. It is reproducible for several different crystal size samples. Simple molecular mechanics calculations for the ZSM-5/argon system allow interpretation of the observed isotherms. We found that: • We can identify the individual sorption features for argon in ZSM-5. • The first argon atom sorbing in the ZSM-5 unit cell can be discerned. • Initial argon sorption in ZSM-5 occurs in the 10-ring structures. The calculations employed are able to describe the main features of the observed isotherms but are not sufficiently refined to deal with the fine structure. © 1993 by Academic Press, Inc.