Propane Conversion to Aromatics on Highly Active H-GaAlMFI: Effect of Thermal Pretreatment

The propane aromatization activity over H-GaAlMFI has been investigated after different thermal pretreatments (calcination temperature range: 500−800 °C) at a reaction temperature of 500 °C and in the space velocity range of 1500−12000 cm 3 /g/h. The calcination temperature had a strong influence on the strong acidity of the zeolite, propane conversion, and aromatic distribution. The decrease in acidity with increased thermal treatment severity correlated well with the decrease in the framework Ga. There was a considerable decrease in propane aromatization activity at calcination temperatures above 600 °C. The effect of calcination temperature on the propane aromatization activity can be explained in terms of change in the strong acidity of the zeolite and the extraframework Ga content. The selectivity for aromatics was found to decrease with increasing thermal pretreatment severity, while that for methane, ethane, and propylene was found to increase. The aromatic distribution was also influenced by the thermal pretreatment; the selectivity for benzene increased with increasing pretreatment temperature, while the selectivity for toluene, C 8 aromatics, and C 9+ aromatics decreased.