Structure and catalytic properties of Ga-MFI in propane aromatization Original Research Article

The structure–activity relationship in the dehydrogenation steps in propane-aromatization was examined by using MFI-type gallosilicate catalysts containing various amounts of gallium and calcined at various temperatures. The characterization by TPD of ammonia and TEM indicated that, with increasing gallium content, both the zeolitic acidity and the extraframework Ga2O3 increased, and that, with increasing calcination temperature, the number and the particle size of extraframework Ga2O3 species increased while the strong acidity decreased. The reactions of propane and cyclohexane were conducted to evaluate the catalytic activity, especially in the dehydrogenation steps in propane-aromatization, and it was found that the activity was strongly influenced by the calcination temperature. In the case of high gallium content, the conversions of propane and cyclohexane decreased with the calcination temperature, while in the case of low gallium content the conversions increased. The former result was attributed to the decrease in the acid amount due to the extraction of gallium from the MFI-framework, and the latter result to the increase in the number and the size of extraframework Ga2O3 particles.