Structural characterization of MCM-41 over a wide range of length scales

Abstract

In the present work the meso- and macrostructural characteristics of the recently developed model mesoporous adsorbent MCM-41, of different pore diameters, prepared in our laboratory, have been estimated with the help of various techniques. The structure is found to comprise four different length scales¯those of the mesopores, the crystallites, the grains, and the particles. It was also found that the surface area estimated by the use of small angle scattering techniques is higher, while that estimated by mercury porosimetry is much lower, than that obtained from gas adsorption methods. On the basis of the macropore characterization by mercury porosimetry, and the considerable macropore area determined, it is seen that the actual mesopore area of MCM-41 may be significantly lower than the BET area. TEM studies indicated that even though MCM-41 does not have an ideal mesopore structure (because of the presence of curved pore channels), it may still be treated as a model mesoporous material for gas adsorption studies because of the large radius of curvature of the channels.