CHARACTERIZATION OF ACID-ACTIVATED MONTMORILLONITE AND VERMICULITE CLAYS BY THERMAL-DESORPTION AND DIFFERENTIAL SCANNING CALORIMETRIC TECHNIQUES

Montmorillonite and vermiculite clays, activated with hydrochloric aci d solutions of different concentrations, have been characterized by th ermal desorption and differential scanning calorimetric (DSC) techniqu es using ammonia and pyridine as probe molecules. The amount of adsorb ed ammonia is found to be about twice the amount of pyridine on all th e samples as determined by thermal desorption studies. DSC studies rev eal the heterogeneity of acidic sites on the activated catalysts. DSC thermograms show the existence of three distinct acidic sites with dif ferent strength on the surface of the catalysts.