Common clays investigated for use as high tech environmental catalysts

Textural properties as a function of the starting mineral particle size

Development of new clean technologies in accordance with increasingly demanding environmental legislation requires new catalysts, adsorbents and/or catalyst supports. Clays have been identified as a promising materials resource for this application.
More specifically, Pillared Inter-Layered Clays (PILCs) have been identified as suitable for these purposes. However, their widespread use has been delayed by difficulties in obtaining a uniform and reproducible product.

Engineers and scientists from the Universidad de la República, M. Sergio, M. Musso, J. Medina and W. Diano, studied the influence of the starting material particle size on the textural properties of the pillared clays obtained by using the mineral without any other pretreatment than drying, grinding and sieving.

In their study, they transformed a Uruguayan montmorillonitic mineral into a microporous solid by pillaring. Using three different size fractions, they were in all cases able to produce yields upwards of 90%.

No significant difference was observed for particle sizes below 450 m m. Resultant microporous solids were obtained with specific surface areas over 350 m 2/g and specific total pore volume of about 0.250 mL/g. The specific micropore volumes represented about 70% of the total pore volume. Pore openings, determined by two independent methods, were in the range of 0.7-0.8 nm. The samples calcined at 750 oC retained about 72% of their textural parameter values.

The study showed that a high mineral yield and a simpler manipulation can yield economic advantages in producing microporous solids. The high mineral yield could be used in catalysis and adsorption processes, especially if size or form selectivity are required.