OXIDATION OF ORGANIC-MATTER IN POWDERED CLAYS AT TEMPERATURES LOWER THAN DEHYDROXYLATION TEMPERATURE OF CLAY-MINERALS .2. KINETICS

The kinetics of oxidation of organic matter in two naturally occurring clays containing 0.5 and 2% organic matter have been investigated ove r a range of temperatures, 300-450 degrees C, and oxygen partial press ures, 0.21-0.56 atm. Application of the shrinkage core model for two g eometries, spherical (discrete particles of matter) anti slab (layers of matter), gave poor correlation with the experimental results. A rev ised version of the shrinking core model was developed which rakes int o account that the form and composition of organic matter present in n atural clays are variable, and gave goon correlation with the experime ntal results for both geometries and both days. A high activation ener gy 128-153 kJ mol(-1), was calculated for the oxidation process. If is concluded that the chemical reaction is the overall rate controling s tep in the oxidation process. (C) 1997 The Institute of Materials.