Pore-volume and surface area in microporous–mesoporous solids

To show the correct evaluation of pore-volume and surface area in microporous–mesoporous samples a series of mechanical mixtures of microporous zeolite NaY and mesoporous γ-alumina was prepared. The nitrogen adsorption isotherms (77 K) were analyzed by the modified (three parameters) BET equation and compared with the independent textural information obtained (a) from t-plots (with the standard isotherm of nonporous α-alumina and the standard isotherms of Lecloux–Pirard); and (b) by subtracting the isotherm of the parent NaY from mixed sample isotherms.For illustration, the failure of the classic (two-parameter) BET equation for samples of that type was demonstrated.