Effects of Ga content and reaction pressure upon the aromatization of propane over H–Ga–Al-bimetallosilicate catalysts

Aromatization of propane has been investigated at 540 °C in a reaction pressure range up to 0.686 MPaG over MFI-type H–Ga–Al-bimetallosilicates having various Ga/(Ga + Al) atomic ratios but a constant Si/(Ga + Al) ratio of 15. Both the propane conversion and the aromatic selectivity increased with increasing the Ga/(Ga + Al) ratio up to 0.25. Further increase in the Ga content decreased the propane conversion, although the aromatic selectivity increased. Of the catalysts examined, the H–Ga–Al-bimetallosilicate sample having the Ga/(Ga + Al) ratio of 0.25 showed the highest performance for propane aromatization. The effect of reaction pressure was investigated using this catalyst. With increasing the reaction pressure, the propane conversion increased, but the aromatic selectivity decreased. The reaction pressure was also found to strongly influence the cracking activity and the deactivation rate of the catalyst. From the analysis of the gaseous products, it was concluded that the aromatization reaction was suppressed under high reaction pressure conditions because of the formation of methane and ethane by protolytic cracking and hydrogen transfer from aromatic precursors to olefinic intermediates.