N2 sorption scanning behavior of SBA-15 porous substrates

Abstract

The independent non-intersecting cylindrical pore nature of SBA-15 materials represents, in principle, a very adequate experimental system to analyze the N2 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 N2 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.