Hierarchical Meso-Microporous ZSM-5 Zeolite for Producing Light Olefins by Catalytically Cracking Oleic Acid

The introduction of mesopores to zeolite crystals via small organic templates has attracted widespread attention. In this study, we used cetylpyridinium bromide (CET–PyBr) to direct the synthesis of hierarchical meso-microporous ZSM-5 zeolite (HMM). By varying the CET–PyBr and sodium sulfate contents in the initial gel, the pore structure and acidity of the HMM were systematically modified. X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption were utilized to investigate HMM’s mesoporous network. In HMM, mesopore formation was attributed to the assembly of nanocrystal clusters. By optimizing the organic templates, the HMM formation mechanism was elucidated. The acidities of the HMM catalysts were further characterized using temperature-programmed ammonia desorption, magic angle spinning nuclear magnetic resonance, and Py-IR spectroscopy. At 500 °C, the catalytic cracking of oleic acid over HMM yielded up to 54.0% light olefins, and HMM maintained its activity for up to 40 h. HMM’s homogeneous mesopores and moderate acidity contributed to its extended lifespan and enhanced its gaseous product yield.