Effect of cobalt in activity reduction of close aluminums in the HZSM-5 framework and its role in enhancing light olefins production in Catalytic cracking of LPG fuel

In this investigation, HZSM-5 zeolite with AlCl3 as aluminum source were synthesized by hydrothermal method and modified with cobalt. HZSM-5 and Co/HZSM-5 zeolites were used to investigate the product distribution in LPG fuel cracking. The prepared HZSM-5 and Co/HZSM-5 catalysts were characterized by XRD, FTIR, SEM, BET, XRF, NH3-TPD and Al MAS NMR analyses. The results of NH3-TPD showed that the acidity of Co/HZSM-5 zeolite was lower than HZSM-5. Aluminum distribution in the framework of HZSM-5 was determined by chemical analysis of XRF and reflectance UV-Visible analysis. The results indicated that the proportion of close Al atoms and single Al atoms in the zeolite framework was found to be 28.6% and 71.4%, respectively. The obtained olefin yield for Co/HZSM-5 (48.1%) was higher than HZSM-5 (45.4%) in catalytic cracking of LPG fuel. The yield of C5 heavy products, the formed coke and deactivation rate for Co/HZSM-5 catalyst were lower than unmodified HZSM-5.