Catalytic cracking of n-heptane over Fe modified HZSM-5 nanosheet to produce light olefins

Aiming at the acid modification and stabilization of ordered mesopores in HZSM-5 nanosheet (NS) zeolite for catalytic cracking, two kinds of Fe-modified NS zeolite catalysts were prepared by incipient wetness impregnation (Fe/NS) and an in-situ hydrothermal synthesis method ([email protected], N-[3-(trimethoxysilyl)propyl]ethylenediamine complexed Fe as precursors). Fe modification conveyed a lower n-heptane cracking conversion by the Fe/NS catalyst because of the decreased total acid content compared with the parent NS catalyst. However, the decreased Brønsted to Lewis acid ratios by Fe modification restricted the deep hydrogen transfer of olefins, leading to an enhanced ethylene and propylene yields in the product. Furthermore, for [email protected] catalyst, the highly dispersed FeOx between the nanosheet layers stabilized the mesopore arrangement, and the facilitated diffusion by highly connected channels further alleviated olefin consuming. At reaction temperature of 550 °C with a weight hourly space velocity of 8.64 h−1, a 41.8 wt% yield of light olefins (ethylene of 12.2 wt% and propylene of 29.6 wt%) by the [email protected] catalyst was realized, which was 10.4% and 21.7% higher than that of the Fe/NS and parent NS catalysts, respectively. Moreover, [email protected] also showed a good catalytic stability with a deactivation rate of only 4.37% after 18 h reaction.