N-Heptane catalytic cracking on ZSM-5 zeolite nanosheets: Effect of nanosheet thickness

Abstract

To explore the effect of channel properties on catalytic activity, ZSM-5 zeolite nanosheets were synthesized with di-quaternary ammonium-type surfactant and used in n-heptane cracking reaction. Nanosheet thickness was changed from around 4 nm–20 nm by adjusting the ratio of surfactant to tetraethyl orthosilicate (TEOS). The synthesized zeolite nanosheets were characterized by physical and chemical adsorption, electron microscopy, X-ray diffraction (XRD), pyridine infrared (Py-IR), Thermogravimetric analysis (TGA) and Raman spectra. The results showed that zeolite with thicker nanosheets had more microporosity and was more conducive to remarkably improving the selectivity of light olefins. High mesoporosity of zeolite nanosheets greatly reduces the diffusion resistance and accelerates mass transfer which even increases the direct diffusion of insufficiently cracked intermediates. Thicker zeolite nanosheets with more micropores prolong the reaction time and thus improve the selectivity of target products. • Ordered mesoporous nanosheet zeolites were synthesized and used in catalytic cracking reaction. • Nanosheet thickness was regulated from around 4 nm–20 nm through the change of template concentration in synthetic gel. • Thicker nanosheet zeolite with more micropores was conducive to the production of ethylene and propylene. • A well linear dependence was found between total selectivity and HFʺ.