Preparation of Al-pillared montmorillonite from concentrated dispersions

Clays may be modified by introducing hydroxycations between the layers to obtain microporous solids with catalytic or adsorption properties. This study presents the differences occurring in samples when different Al/clay ratios are applied in pillaring a montmorillonite with aluminum. XRD, FTIR, 27Al MAS NMR, nitrogen adsorption isotherms and ammonia adsorption were applied in order to study the structure and properties of pillared materials. Besides the aluminum-forming pillars, we found a fraction of aluminum retained on the clay surface, its extent depending on the Al/clay ratio. This fraction, mainly in tetrahedral coordination, is a result of the pillaring process and especially affecting the textural properties and, to a lesser degree, the acidity. A relation between pillar density and acidity was also found.