Thermal decomposition of TPA-ZSM-5 zeolites: effect of gas atmosphere and Si/Al ratio

Abstract

The thermal analysis of TPA-ZSM-5 (Si/Al = 13.6-39.7) and TPA-silicalite in the presence of inert and oxidizing gas atmospheres has been carried out in the temperature range 303-1273 K. The decomposition of TPA cations in the presence of air is a complex exothermic process. It occurs in two steps, one between 663 and 773 K and the other between 773 and 973 K. However, the decomposition in inert (nitrogen) atmosphere is endothermic and occurs in a single step and also at lower temperatures ( < 773 K). The decomposition is strongly influenced by the Si/Al ratio. The TPA cations associated with the acid sites are more stable than those associated with the non-acid sites of the zeolite. The activation energy of the decomposition increases with the increase in the Al content of the zeolite.