Comparative textural study of highly ordered silicate and aluminosilicate mesoporous mesophase materials having different pore sizes

Honeycomb structure model was applied for describing surface properties in the MCM-41 and SEA-15 types of highly ordered silicas and aluminosilicates with different nominal mesopore diameters: about 4 nm and about 10 nm. As shown, calculations of internal specific surface area A(me) require a heterogeneity of this surface to be taken into account, the latter being quantified by the roughness coefficient beta. These calculations at the condition beta = 1.0 will allow to estimate the lower limit of specific surface area of the materials only. which will correspond to the perfectly smooth walls of mesopores. This description seems to be valid for the MCM-41 type systems, for which beta is about 1.1-1.2. On the contrary, beta is found to exceed 1.5 for the SEA-15 type materials. This fact is probably due to an essential non-smoothness of the mesopore surface in these systems and may be associated with their synthesis conditions. (C) 2001 Elsevier Science B.V. All rights reserved.