The adsorption isotherms of mesoporous MCM-41 molecular sieve and supported MCM-41 catalysts have been investigated. These iostherms are highly abnormal as they not only exhibit two regions in their reversible parts, but also two hysteresis loops. The first discovered low pressure hysteresis at relative pressure below 0.4 is assigned to the capillary condensation in the mesoporous channels, whereas the hysteresis near saturation pressure is assigned to the capillary condensation in the mesopores between aggregates of the molecular sieve. The adsorption isotherms together with the XRD patterns of the samples can be used to characterize the orderliness of the structure and the accessibility of the mesoporous channels of MCM-41 effectively.

Key words: CATALYST, X-RAY DIFFRACTION ANALYSIS, MOLECULAR SIEVE, ADSORPTION ISOTHERM