The anomalous sorptive behaviour of Zsm-5 and silicalite-I: Observation of low-pressure hysteresis in nitrogen adsorption

Abstract

A first stage of a systematic study of the nature of the low-pressure hysteresis loop observed in the nitrogen adsorption isotherms of some MFI zeolites is presented. It was shown that the pressure at which occurrence of this hysteresis loop takes place was linked to the presence of defect sites. The role of the exchangeable cation was also investigated, and it was suggested that in addition to the numbers of defect sites present, the strength of adsorbate-adsorbent interaction, and probably pore shape was also involved.