ZSM-5@KIT-6-encapsulated composite molecular sieves for the catalytic cracking of waste cooking oil model compound to produce light olefins

BACKGROUND A series of ZSM-5@KIT-6 composite molecular sieve catalysts was prepared by encapsulating ZSM-5 as a substrate in the mesoporous material KIT-6. The intent was to use these catalysts to promote the catalytic cracking of a waste cooking oil model compound (WCOMC) to produce light olefins. RESULTS The morphology, structural characteristics and acidity of each of the resulting catalysts were characterized by X-ray diffraction, transmission electron microscopy, N 2 -Brunauer–Emmett–Teller (N 2 -BET) surface area analysis and temperature-programmed ammonia desorption. The results showed that ZSM-5 was successfully coated with KIT-6. The BET surface areas of these catalysts ranged from 345 to 792 m 2 g −1 and the specimens had average pore sizes in the range of 2.37–5.51 nm. Total acidity increased with increases in the mass-based proportion of ZSM-5 in the material. CONCLUSION The catalytic cracking of WCOMC was studied in a lab-scale fixed-bed apparatus. Trials at a reaction temperature of 600 °C using the material having a mass-based ZSM-5 proportion of 80.0% (ZK-80) gave the highest gas-phase yield of light olefins of 43.8%. After 6000 min, the catalytic performance of this material remained stable, demonstrating a resistance to carbon deposits. The superior activity of the present composite catalysts can be ascribed to improvements in pore structure and acid strength distribution. © 2023 Society of Chemical Industry (SCI).