Rezumat
The behaviour of palygorskite as an adsorbent or catalyst support is governed mainly by the magnitude of its surface areas and degree of surface activity. Most heterogeneous catalytic reactions take place at elevated temperature. It is important and necessary to known the possible changes in physico- chemical properties and hence the catalytic activity due to the thermal treatment. The present work investigates the effect of heat treatment on the surface and textural properties of palygorskite and acid activated palygorskite. Samples were heated at required temperature (150°C, 350°C, 550°C and 750°C) for four hours. Chemical analysis, X ray diffractions, thermal analysis and textural properties evaluated on the basic of nitrogen adsorption have been reported for different samples. Acid-treated samples showed a shift of DTA curves maxima to low temperature with increasing acid treating time. The weight loss observed between 300-900°C was approximately half of the value observed for the untreated mineral over the same temperature range. On heating, water molecules are removed causing changes in the BET surface area and the porosity. The modification as function of the temperature differs with sample. However, at 750°C noticeable decrease of surface area, attributed to closure of mesoporosity, was observed for all the samples.