Abstract
The competitive ion exchange of polycations has been used to prepare well ordered Ti, and Fe-pillared clays of high specific surface area from montmorillonite, and from a beidellitic clay either natural or acid treated. The competitor are Al polycations added to the pillaring solutions. The method has been applied to unpurified natural clays, giving PILCs with surface areas of around 250 m 2/g after drying at 523 K. The thermal stability of the resulting solids is increased with surface areas as high as 130–220 m 2/g after calcination at 773 K. The competitive ion exchange has been also applied to acid treated clays, with surface areas of the PILC reaching 200 m 2 g − 1 . The acid properties of these PILC, determined by microcalorimetry using NH 3 adsorption, are comparable to those of zeolites or supported heteropolyacids, with initial heats of adsorption of 150–160 kJ mol − 1 and site density of around 2 μmol/m 2. This acidity overpass that of pillared montmorillonites and saponites prepared by a conventional method. The acid-activated clays pillared by this procedure show a lower acidity than the pillared materials obtained from natural clays.
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