Title : Aromatization of propane using GaAlMFI based catalyst
The aromatization of propane was performed over MFI-type Gallo-alumino-silicate (GaAlMFI) catalysts shaped to extrudates using nano-sized oxides (i.e. SiO2 or Al2O3). The GaAlMFI zeolites were hydrothermally synthesized having different Ga/(Ga+Al) and Si/(Ga+Al) ratios. It was observed that propane conversion and aromatic yield depend mainly on zeolite components in the case of either with or without nano-sized oxide. Both propane conversion and the aromatic yield on the catalyst were increased with an increase in Ga/(Ga+Al) ratio until an optimum value of ~0.3 in the zeolite. The dehydrogenation was increased with an increase in the Ga/(Ga+Al) ratio of the zeolite component due to an increase in non-framework (nfw) gallium species. The selectivity of aromatization to cracking (A/C) ratio in the case of the shaped catalyst with nano-sized oxides was remarkably increased with an increase in Ga/(Ga+Al) ratio of zeolite component due to a decrease in strong acid sites. The propane conversion and aromatic yield were also observed to increase with the increase in Si/(Ga+Al) ratio until an optimum value of ~20 and then dropped sharply. The A/C ratio passed through a maximum corresponding to the optimum value of ~20 for the Si/(Ga+Al) ratio and then decreased with an increase in the Si/(Ga+Al) ratio. The performance of the catalyst with nano-sized Al2O3 was better than that of the catalysts with nano-sized SiO2 or without nano-sized oxides. The calcination temperature of 550 ?C for the zeolite in the catalyst of GaAlMFI with nano-sized Al2O3 was observed to be the optimum resulting in maximum propane conversion and aromatic yield. The degree of aromatization to dehydrogenation (A/D) and A/C ratios were observed to pass through maxima at a calcination temperature of 550 ?C and then decreased with further increase in calcination temperature. It was confirmed by XPS that the nano-sized alumina promotes the formation of non-framework gallium species.