Advantages of Porous H-ZSM-22 Zeolite for Catalyzing Oleic Acid Isomerization: High Selectivity and Regeneration Stability

In this study, highly crystalline ZSM-22 zeolite with a TON topology was synthesized via a seed–template co-assisted hydrothermal method and subsequently modified with low-concentration NH₄Cl to introduce Brønsted acid sites. The characterization of the catalyst revealed its well-defined rod-like crystals (2–5 μm), one-dimensional straight channels (0.46 × 0.57 nm), microporous surface area of 210 m 2 ·g −1 , Brønsted-to-Lewis (B/L) acid ratio of 0.45, and excellent thermal stability. Under optimized reaction conditions (270 °C, 3 h, 6 wt% catalyst), the catalyst achieved a 95.01% conversion of oleic acid and a 77.72% yield of isostearic acid. The confinement effect of the 1D channels effectively suppressed undesired side reactions, offering significantly enhanced selectivity compared to commercial zeolites such as ZSM-5. Thermogravimetric analysis demonstrated that calcination at 550 °C successfully removed coke deposits and restored catalyst activity. After five regeneration cycles, the conversion and yield remained at 89.50% and 72.80%, respectively, with less than 6% loss. These findings provide theoretical and technical guidance for the high-value catalytic transformation of biomass-derived fatty acids. Graphical H-ZSM-22 catalyst with good reusability