Effect of ZSM-5 Particle Size and Framework Silica-to-Alumina Ratio on Hexane Aromatization

Abstract

Parent ZSM-5 and Ga-modified ZSM-5 catalysts with different Si/Al ratios and particle sizes were prepared. The physicochemical properties of the prepared catalysts were investigated by performing X-ray powder diffraction analysis, BET surface area analysis, and NH₃-TPD analysis. The performance of the aromatization reaction of the prepared catalysts was evaluated with 1-hexane as a model compound. The zeolite catalysts with a low SiO₂/Al₂O₃ ratio possessed better activity than those with a high SiO₂/Al₂O₃ ratio. Ga modification significantly improved the catalyst aromatization selectivity. Through aromatization, the acid sites of Ga-modified nano-sized zeolites promoted the selective conversion of produced olefin to aromatics by removing H-atoms. For the parent ZSM-5 and Ga-modified catalysts, the catalyst stability increased with an increase in the SiO₂/Al₂O₃ molar ratio. The nano-sized ZSM-5 catalyst with a high SiO₂/Al₂O₃ ratio exhibited better catalytic stability than the microscale ZSM-5, and the nano-sized catalyst with a low SiO₂/Al₂O₃ ratio showed very low stability.