Insight into stepwise dealumination in acid-treatment of IM-5 for catalytic cracking of n-heptane and Fischer-Tropsch naphtha

10-membered ring IM-5 zeolite has shown excellent performance in many catalytic reactions. The efficient preparation of high silica by situ synthesis remains huge challenge. Here, with SiO2/Al2O3 ratio (SAR) 49–116 was acquired HNO3 treatment. An interesting stepwise dealumination behavior discovered during the whole acid-treatment process (based on XRF characterization). Extra-framework Si (EF-Si) compensated for defects framework, thereby postponed removal Al species at initial period acid treatment, as indicated 27Al, 29Si, 1H NMR and density-functional theory (DFT) calculations. dealuminated were revealed to retain more than 83 % crystallinity little loss micropore volume. Bimolecular reaction predominant n-heptane cracking resulted from decreased amount strength IM-5. Meanwhile, improved overall yields light olefins liquid petroleum gas (LPG) less coke production Fischer-Tropsch naphtha (FT-naphtha) reaction.