Influence of preparation method on thermal stability and acidity of Al-PILCs

In general, clays may be modified introducing hydroxications. between the constituent layers to obtain microporous solids, known as pillared clays (PILCs), useful in adsorption and catalysis. In this work, XRD, FT-IR, N-2 adsorption isotherms and ammonia adsorption techniques were applied to study the changes in structure and properties provided to a montmorillonite through pillaring when different preparation methods, Al/clay ratio and drying procedures are used in the synthesis. Above a certain Al/clay ratio, pillar density is addressed by the maximum exchange capacity of the clay at the pH of the pillaring solution. Under such a situation, micro- and meso-porosity remain almost unchanged whereas macroporosity is fully dependent on the concentration of the clay suspension and more on the drying conditions of the flocculated exchanged clay layers. Thermal analysis has shown as a useful tool to understand the changes in acidity with the temperature. (C) 2001 Elsevier Science B.V. All rights reserved.