The effect of heating rate and gas atmosphere on template decomposition in silicalite-1

Template evolution from TPABr/silicalite powder was studied in a thermogravimetric analyzer as a function of heating rate and gas atmosphere to determine the maximum rate of weight loss and the temperature at which the rate of weight loss was a maximum. Through the application of TPD theory, the activation energies of the thermal decomposition reactions in various gaseous atmospheres (helium, oxygen, air, ozone/air mixture) were also calculated. The results of these investigations showed that an increased calcination heating rate had a direct correlation with an increased rate of weight loss. The template removal reaction in an inert atmosphere (helium) was endothermic; however, the presence of oxidizing components in the gas atmosphere gave rise to significant exothermic reactions. We found that the least stressful conditions for template removal occurred with a heating rate of 0.5 K/min in an atmosphere containing a mixture of air and ozone (1%). For these conditions, the maximum rate of weight loss was 0.061%/min, and the temperature at maximum weight loss was 487 K; the template was fully removed at a final temperature of ca 723 K.