A Nanocrystalline ZSM-5 for the Catalytic Cracking of Waste Cooking Oil

Graphical A series of hierarchical ZSM-5 nanocrystalline aggregates (HNZ-5) was synthesized for the catalytic cracking of model waste cooking oil model compound (WCOMC) to produce light olefins. A series of hierarchical ZSM-5 nanocrystalline aggregates (HNZ-5) was synthesized using a hydrothermal method with tetrapropylammonium hydroxide as a structural guide. The HNZ-5 samples having different Si/Al molar ratios all showed suitable hierarchical architectures and the maximum surface area was found to be 329 m 2 /g. The SEM image displayed the width of the individual crystal particles was ~100 nm, and its nanocrystalline clusters generated intercrystalline pores. Temperature-programmed desorption with NH 3 indicated that the total acidity of this material increased with increases in the Al 3+ content to a maximum of 0.47 mmol/g at a Si/Al ratio of 15. In addition, 27 Al magic angle spinning nuclear magnetic resonance spectra showed that the acid sites were associated with tetrahedral and octahedral Al sites. This HNZ-5 was applied to the catalytic cracking of waste cooking oil model compound and gave a light olefin yield as high as 43.9 % at 550 °C. Extending the reaction time to 6000 min provided a yield of light olefins in excess of 30 %, which was higher than that achieved using traditional ZSM-5. These data confirmed that the hierarchical pore structure of HNZ-5 resulting from the self-assembly of nanocrystals, together with exposed acidic sites, promoted the catalytic conversion of large molecules.