EFFECT OF PORE-SIZE ON ADSORBATE CONDENSATION AND HYSTERESIS WITHIN A POTENTIAL MODEL ADSORBENT - M41S

The use of M41S (MCM-41) materials, which have cylindrical-like mesopores, has highlighted the effect of pore diameter on the position, presence and size of the hysteresis loop observed in association with argon and nitrogen adsorbate-adsorbate co-operative condensation. A distinct step in the adsorption isotherm was observed for each of three materials with varying pore diameters (2.5, 4.0 and 4.5 nm). An increase in the pore size leads to a shift in this step to higher relative pressures and to the appearance of a significant hysteresis loop. This may indicate the transition from secondary micropores to mesopores with respect to the nitrogen adsorbate.