Cracking and aromatization properties of some metal modified ZSM-5 catalysts for light alkane conversions

Abstract

ZSM-5 (HZ) was prepared by hydrothermal synthesis and, zinc and gallium incorporated ZSM-5 catalysts were prepared by adopting incipient wet impregnation (ZnHZ, GaHZ) and co-synthesis methods (Zn-Al-Si and Ga-Al-Si). The acidity and strength distribution of acid sites were measured by micro-calorimetric ammonia adsorption, where Zn-Al-Si and Ga-Al-Si exhibited lower acidity values when compared to the HZ, ZnHZ and GaHZ samples. The n-heptane aromatization activity of the catalysts is in the order of Zn-Al-Si>Ga-Al-Si>ZnHZ~GaHZ>HZ. The Zn-Al-Si catalyst exhibited the lowest acidity but highest aromatization activity with stable performance in the studied period of 360 min. The catalyst exhibited greater than 80% conversions with 50-65 wt.% selectivity to aromatics for the conversion of various industrial feedstocks namely NGC, light naphtha and raffinate. The major byproduct in this reaction is 21-33 wt.% LPG that makes the catalyst promising for industrial application.