Template-Free Synthesis of ZSM-5 Zeolite with Tunable Acidity and Diffusion for Efficient Cyclohexene Hydration

The cost-effective synthesis of ZSM-5 zeolite with tailored acidity and diffusion properties is essential for advancing its industrial application in cyclohexene hydration to cyclohexanol. Here, a series of ZSM-5 zeolite catalysts were successfully synthesized via a seed-induced, template-free crystallization method by varying the SiO2/Al2O3 ratio (SAR, 15–100) and seed suspension addition (0.5–20 wt %), followed by the systematic evaluation of their catalytic performance in cyclohexene hydration. Comprehensive physicochemical studies reveal that all samples possess highly crystalline MFI structures, with SAR primarily modulating acidity and seed addition controlling crystal size. The SAR = 50 sample with a proper acidity demonstrates optimal performance under optimized conditions (120 °C, 4 h, cyclohexene-to-water volume ratio = 1), achieving a cyclohexanol yield of 10.7%, comparable to commercial ZSM-5 (10.2%). Critically, based on the reaction results, the correlation between physicochemical properties and hydration activity is elucidated. This work validates the industrial potential of template-free synthesized ZSM-5 zeolite and provides novel insights for developing cost-effective, high-performance catalysts.