N2 sorption scanning behavior of SBA-15 porous substrates

The independent non-intersecting cylindrical pore nature of SBA-15 materials represents, in principle, a very adequate experimental system to analyze the N-2 sorption scanning behavior according to the theorems of the Independent Domain Theory of Sorption Hysteresis. In this work, SBA-15 materials of two general types have been synthesized: (i) substrates made by hexagonal arrays of cylinders of about the same sizes, and (ii) solids including a relatively wide distribution of cylindrical pores of varying diameters arranged in a fairly distorted hexagonal packing. Boundary and primary N-2 sorption scanning curves have been experimentally determined on all these materials in order to observe the possible irruption of cooperative processes during the filling and emptying of tubular SBA-15 pores. Pore domain complexion diagrams (i.e. graphs indicating the amount of pore sizes that are occupied by condensate or vapor) have been constructed by means of Non-Local Density Functional Theory calculations of the pore-size distributions that are incumbent to both boundary and primary scanning curves. It has been inferred that two phenomena branded as advanced adsorption and single pore-blocking can take place in reason of the undulating cross-section nature of some SBA-15 tube materials; the extents of the above irreversible processes depending on the degree of sinuosity of the cross sections of the tubes. (C) 2004 Elsevier B.V. All rights reserved.