High resolution argon adsorption isotherms for various zeolites

Ar isotherms (87.3 K) and N-2 isotherms (77.4 K) were measured for two silicas with different silanol content and two MFI zeolites with different alumina (proton) content. Silanols or protons give the significant effect on N-2 isotherms, but has little influence on Ar isotherms. Ar isotherms for seven zeolites of various micropore size were measured in the pressure range of p/p(o) = 10(-7)-0.99. Zeolites used are MFI (ZSM-5), MTW (ZSM-12), AFI (SSZ-24), AFI (AlPO-5), VFI (VPI-5) [group A], and LTA (Type A-Ca), FAU (Type Y) [group B]. Group A zeolites have micropore channels without cage, while group B zeolites have the window and cage. It has been found that the Polanyi adsorption potential of Ar atoms for the group A zeolites is closely related with channel size, and the adsorption potential of the group B zeolites depends on both of cage size and channel size.