THERMAL-DECOMPOSITION OF POTASSIUM CHLORATE IN THE PRESENCE OF CHROMIUM(III) OXIDE

The effect of the addition of chromium(III) oxide on the thermal decom position of potassium chlorate (PC) was studied using TG and DTG. Oxid e samples were prepared by calcination of Cr(NO3)3.9H2O and of chromia gel, as precursors, between 500 and 800-degrees-C. It was found that an oxide concentration of 10 wt.% by weight of PC was sufficiently act ive. Oxide activity was lowered as its calcination temperature was inc reased. Oxides prepared at 500-degrees-C from different precursors wer e characterized by X-ray powder diffraction to be Cr2O3. The DTA for P C showed one endotherm at 361-degrees-C due to fusion. This was follow ed by two exotherms at 426.8 and 442-degrees-C related to the decompos ition of PC and separation of KCl. DTA curves of the catalyzed decompo sition of PC exhibited a new exotherm at 415-degrees-C corresponding t o the formation of K2Cr2O7, followed by an endothermic peak at 420.7-4 36.2-degrees-C due to the melting of K2Cr2O7. IR spectroscopy confirme d the formation of K2Cr2O7 as a solid orange residue. The activation e nergies (DELTAE) of the thermal decomposition of pure PC and PC in the presence of Cr2O3 calcined at 500-degrees-C (from the different precu rsors) under non-isothermal conditions were calculated, from the TG re sults, using the Coats-Redfern equation. The decomposition process was found to obey the first order equation. A correlation between the oxi de precursors and their activities towards the decomposition of PC (DE LTAE values) was made through the calculated amount of excess surface oxygen for each oxide.